From 9e5baacd26b3399a12b7570398a15d3bc631bd7b Mon Sep 17 00:00:00 2001
From: Dan Freeman <dfreeman@salsify.com>
Date: Thu, 12 Dec 2019 18:31:57 +0100
Subject: [PATCH 01/23] Include decorator and class field plugins after
 TypeScript, if present

---
 index.js                 | 6 +++---
 node-tests/addon-test.js | 6 ++++++
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/index.js b/index.js
index 6010ab74..68e05ab5 100644
--- a/index.js
+++ b/index.js
@@ -340,7 +340,8 @@ module.exports = {
         plugins,
         [require.resolve('@babel/plugin-proposal-decorators'), { legacy: true }],
         {
-          before: ['@babel/plugin-proposal-class-properties', '@babel/plugin-transform-typescript']
+          before: ['@babel/plugin-proposal-class-properties'],
+          after: ['@babel/plugin-transform-typescript']
         }
       );
     }
@@ -357,8 +358,7 @@ module.exports = {
         plugins,
         [require.resolve('@babel/plugin-proposal-class-properties'), { loose: options.loose || false }],
         {
-          after: ['@babel/plugin-proposal-decorators'],
-          before: ['@babel/plugin-transform-typescript']
+          after: ['@babel/plugin-proposal-decorators', '@babel/plugin-transform-typescript']
         }
       );
     }
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index b4429b48..8265e81b 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -792,6 +792,12 @@ describe('ember-cli-babel', function() {
 
       expect(loosePlugins[1][1].loose).to.equal(true, 'loose setting added correctly');
     });
+
+    it('should include class fields and decorators after typescript if detected', function() {
+      let plugins = this.addon._addDecoratorPlugins(['@babel/plugin-transform-typescript'], {});
+      expect(plugins[0]).to.equal('@babel/plugin-transform-typescript', 'typescript still first');
+      expect(plugins.length).to.equal(3, 'class fields and decorators added');
+    });
   });
 
   describe('_shouldIncludeHelpers()', function() {

From f602be43632f20dffb36ac4972481bd73adb173e Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 03:26:42 -0500
Subject: [PATCH 02/23] feat: add TypeScript tranform when e-c-ts >=
 4.0.0-alpha

---
 index.js     | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 package.json |  3 ++
 yarn.lock    | 41 ++++++++++++++++++++++++-
 3 files changed, 127 insertions(+), 2 deletions(-)

diff --git a/index.js b/index.js
index 68e05ab5..e1a3962e 100644
--- a/index.js
+++ b/index.js
@@ -254,14 +254,20 @@ module.exports = {
   },
 
   _getExtensions(config) {
+    let shouldIncludeTypeScriptPlugins = this._shouldIncludeTypeScriptPlugins();
     let emberCLIBabelConfig = config['ember-cli-babel'] || {};
-    return emberCLIBabelConfig.extensions || ['js'];
+    let extensions = emberCLIBabelConfig.extensions || ['js'];
+    if (shouldIncludeTypeScriptPlugins && !extensions.includes('ts')) {
+      extensions.push('ts');
+    }
+    return extensions;
   },
 
   _getBabelOptions(config) {
     let addonProvidedConfig = this._getAddonProvidedConfig(config);
     let shouldCompileModules = this._shouldCompileModules(config);
     let shouldIncludeHelpers = this._shouldIncludeHelpers(config);
+    let shouldIncludeTypeScriptPlugins = this._shouldIncludeTypeScriptPlugins();
     let shouldIncludeDecoratorPlugins = this._shouldIncludeDecoratorPlugins(config);
 
     let emberCLIBabelConfig = config['ember-cli-babel'];
@@ -292,6 +298,10 @@ module.exports = {
     let userPlugins = addonProvidedConfig.plugins;
     let userPostTransformPlugins = addonProvidedConfig.postTransformPlugins;
 
+    if (shouldIncludeTypeScriptPlugins) {
+      userPlugins = this._addTypeScriptPlugins(userPlugins.slice(), addonProvidedConfig.options);
+    }
+
     if (shouldIncludeDecoratorPlugins) {
       userPlugins = this._addDecoratorPlugins(userPlugins.slice(), addonProvidedConfig.options);
     }
@@ -320,6 +330,79 @@ module.exports = {
     return options;
   },
 
+  _shouldIncludeTypeScriptPlugins() {
+    let checker = new VersionChecker(this.parent).for('ember-cli-typescript', 'npm');
+
+    return checker.gte('4.0.0-alpha');
+  },
+
+  _shouldIncludeOptionalChainingNullishCoalescingPlugins() {
+    let checker = new VersionChecker(this.parent).for('typescript', 'npm');
+
+    return checker.gte('3.7.0');
+  },
+
+  _addTypeScriptPlugins(plugins) {
+    const { hasPlugin, addPlugin } = require('ember-cli-babel-plugin-helpers');
+    const shouldIncludeOptionalChainingNullishCoalescingPlugins = this._shouldIncludeOptionalChainingNullishCoalescingPlugins();
+
+    if (shouldIncludeOptionalChainingNullishCoalescingPlugins) {
+      if (hasPlugin(plugins, '@babel/plugin-proposal-optional-chaining')) {
+        if (this.parent === this.project) {
+          this.project.ui.writeWarnLine(`${
+            this._parentName()
+          } has added the optional chaining plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 and typescript >= 3.7 are installed! You can remove the transform, or the addon that provided it.`);
+        }
+      } else {
+        addPlugin(
+          plugins,
+          [
+            require.resolve('@babel/plugin-proposal-optional-chaining'),
+          ]
+        );
+      }
+
+      if (hasPlugin(plugins, '@babel/plugin-proposal-nullish-coalescing-operator')) {
+        if (this.parent === this.project) {
+          this.project.ui.writeWarnLine(`${
+            this._parentName()
+          } has added the nullish coalescing operator plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 and typescript >= 3.7 are installed! You can remove the transform, or the addon that provided it.`);
+        }
+      } else {
+        addPlugin(
+          plugins,
+          [
+            require.resolve('@babel/plugin-proposal-nullish-coalescing-operator'),
+          ]
+        );
+      }
+    }
+
+    if (hasPlugin(plugins, '@babel/plugin-transform-typescript')) {
+      if (this.parent === this.project) {
+        this.project.ui.writeWarnLine(`${
+          this._parentName()
+        } has added the TypeScript transform plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 is installed! You can remove the transform, or the addon that provided it.`);
+      }
+    } else {
+      addPlugin(
+        plugins,
+        [
+          require.resolve('@babel/plugin-transform-typescript'),
+          { allowDeclareFields: true },
+        ],
+        {
+          before: [
+            '@babel/plugin-proposal-class-properties',
+            '@babel/plugin-proposal-private-methods',
+            '@babel/plugin-proposal-decorators',
+          ]
+        }
+      );
+    }
+    return plugins;
+  },
+
   _shouldIncludeDecoratorPlugins(config) {
     let customOptions = config['ember-cli-babel'] || {};
 
diff --git a/package.json b/package.json
index 296a007d..253abf4e 100644
--- a/package.json
+++ b/package.json
@@ -43,8 +43,11 @@
     "@babel/core": "^7.7.0",
     "@babel/plugin-proposal-class-properties": "^7.7.0",
     "@babel/plugin-proposal-decorators": "^7.7.0",
+    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.7.4",
+    "@babel/plugin-proposal-optional-chaining": "^7.7.5",
     "@babel/plugin-transform-modules-amd": "^7.5.0",
     "@babel/plugin-transform-runtime": "^7.6.0",
+    "@babel/plugin-transform-typescript": "^7.7.4",
     "@babel/polyfill": "^7.7.0",
     "@babel/preset-env": "^7.7.0",
     "@babel/runtime": "^7.7.0",
diff --git a/yarn.lock b/yarn.lock
index eff7b3e8..086dea7d 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -477,6 +477,14 @@
     "@babel/helper-plugin-utils" "^7.0.0"
     "@babel/plugin-syntax-json-strings" "^7.2.0"
 
+"@babel/plugin-proposal-nullish-coalescing-operator@^7.7.4":
+  version "7.7.4"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-nullish-coalescing-operator/-/plugin-proposal-nullish-coalescing-operator-7.7.4.tgz#7db302c83bc30caa89e38fee935635ef6bd11c28"
+  integrity sha512-TbYHmr1Gl1UC7Vo2HVuj/Naci5BEGNZ0AJhzqD2Vpr6QPFWpUmBRLrIDjedzx7/CShq0bRDS2gI4FIs77VHLVQ==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.0.0"
+    "@babel/plugin-syntax-nullish-coalescing-operator" "^7.7.4"
+
 "@babel/plugin-proposal-object-rest-spread@^7.6.2":
   version "7.6.2"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-object-rest-spread/-/plugin-proposal-object-rest-spread-7.6.2.tgz#8ffccc8f3a6545e9f78988b6bf4fe881b88e8096"
@@ -493,6 +501,14 @@
     "@babel/helper-plugin-utils" "^7.0.0"
     "@babel/plugin-syntax-optional-catch-binding" "^7.2.0"
 
+"@babel/plugin-proposal-optional-chaining@^7.7.5":
+  version "7.7.5"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-optional-chaining/-/plugin-proposal-optional-chaining-7.7.5.tgz#f0835f044cef85b31071a924010a2a390add11d4"
+  integrity sha512-sOwFqT8JSchtJeDD+CjmWCaiFoLxY4Ps7NjvwHC/U7l4e9i5pTRNt8nDMIFSOUL+ncFbYSwruHM8WknYItWdXw==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.0.0"
+    "@babel/plugin-syntax-optional-chaining" "^7.7.4"
+
 "@babel/plugin-proposal-unicode-property-regex@^7.7.0":
   version "7.7.0"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-unicode-property-regex/-/plugin-proposal-unicode-property-regex-7.7.0.tgz#549fe1717a1bd0a2a7e63163841cb37e78179d5d"
@@ -529,6 +545,13 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
 
+"@babel/plugin-syntax-nullish-coalescing-operator@^7.7.4":
+  version "7.7.4"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-nullish-coalescing-operator/-/plugin-syntax-nullish-coalescing-operator-7.7.4.tgz#e53b751d0c3061b1ba3089242524b65a7a9da12b"
+  integrity sha512-XKh/yIRPiQTOeBg0QJjEus5qiSKucKAiApNtO1psqG7D17xmE+X2i5ZqBEuSvo0HRuyPaKaSN/Gy+Ha9KFQolw==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.0.0"
+
 "@babel/plugin-syntax-object-rest-spread@^7.2.0":
   version "7.2.0"
   resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-object-rest-spread/-/plugin-syntax-object-rest-spread-7.2.0.tgz#3b7a3e733510c57e820b9142a6579ac8b0dfad2e"
@@ -543,6 +566,13 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
 
+"@babel/plugin-syntax-optional-chaining@^7.7.4":
+  version "7.7.4"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-optional-chaining/-/plugin-syntax-optional-chaining-7.7.4.tgz#c91fdde6de85d2eb8906daea7b21944c3610c901"
+  integrity sha512-2MqYD5WjZSbJdUagnJvIdSfkb/ucOC9/1fRJxm7GAxY6YQLWlUvkfxoNbUPcPLHJyetKUDQ4+yyuUyAoc0HriA==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.0.0"
+
 "@babel/plugin-syntax-top-level-await@^7.7.0":
   version "7.7.0"
   resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-top-level-await/-/plugin-syntax-top-level-await-7.7.0.tgz#f5699549f50bbe8d12b1843a4e82f0a37bb65f4d"
@@ -550,7 +580,7 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
 
-"@babel/plugin-syntax-typescript@^7.2.0":
+"@babel/plugin-syntax-typescript@^7.2.0", "@babel/plugin-syntax-typescript@^7.7.4":
   version "7.7.4"
   resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-typescript/-/plugin-syntax-typescript-7.7.4.tgz#5d037ffa10f3b25a16f32570ebbe7a8c2efa304b"
   integrity sha512-77blgY18Hud4NM1ggTA8xVT/dBENQf17OpiToSa2jSmEY3fWXD2jwrdVlO4kq5yzUTeF15WSQ6b4fByNvJcjpQ==
@@ -803,6 +833,15 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
 
+"@babel/plugin-transform-typescript@^7.7.4":
+  version "7.7.4"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-transform-typescript/-/plugin-transform-typescript-7.7.4.tgz#2974fd05f4e85c695acaf497f432342de9fc0636"
+  integrity sha512-X8e3tcPEKnwwPVG+vP/vSqEShkwODOEeyQGod82qrIuidwIrfnsGn11qPM1jBLF4MqguTXXYzm58d0dY+/wdpg==
+  dependencies:
+    "@babel/helper-create-class-features-plugin" "^7.7.4"
+    "@babel/helper-plugin-utils" "^7.0.0"
+    "@babel/plugin-syntax-typescript" "^7.7.4"
+
 "@babel/plugin-transform-typescript@~7.4.0":
   version "7.4.5"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-typescript/-/plugin-transform-typescript-7.4.5.tgz#ab3351ba35307b79981993536c93ff8be050ba28"

From e2680b1e9af6585fe196805632bc2d81600c8798 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 04:34:25 -0500
Subject: [PATCH 03/23] tests: add tests for _addTypeScriptPlugins()

---
 node-tests/addon-test.js | 52 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 8265e81b..8521515e 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -746,6 +746,58 @@ describe('ember-cli-babel', function() {
     });
   });
 
+  describe('_addTypeScriptPlugins', function() {
+    it('should add only the TypeScript plugin by default', function() {
+      expect(this.addon._addTypeScriptPlugins([], {}).length).to.equal(1, 'plugin added correctly');
+    });
+
+    it('should warn and not add the TypeScript plugin if already added', function() {
+      this.addon.project.ui = {
+        writeWarnLine(message) {
+          expect(message).to.match(/has added the TypeScript transform plugin to its build/);
+        }
+      };
+
+      expect(
+        this.addon._addTypeScriptPlugins([
+          ['@babel/plugin-transform-typescript']
+        ],
+        {}
+      ).length).to.equal(1, 'plugin was not added');
+    });
+
+    it('should add optional chaining and nullish coalescing operator when told to', function() {
+      this.addon._shouldIncludeOptionalChainingNullishCoalescingPlugins = function() { return true; }
+      expect(this.addon._addTypeScriptPlugins([], {}).length).to.equal(3, 'plugins added correctly');
+    });
+
+    it('should warn and not add optional chaining if already added', function() {
+      this.addon._shouldIncludeOptionalChainingNullishCoalescingPlugins = function() { return true; }
+      this.addon.project.ui = {
+        writeWarnLine(message) {
+          expect(message).to.match(/has added the optional chaining plugin to its build/);
+        }
+      };
+
+      expect(this.addon._addTypeScriptPlugins([
+        ['@babel/plugin-proposal-optional-chaining']
+      ], {}).length).to.equal(3, 'plugin was not added');
+    });
+
+    it('should warn and not add nullish coalescing operator if already added', function() {
+      this.addon._shouldIncludeOptionalChainingNullishCoalescingPlugins = function() { return true; }
+      this.addon.project.ui = {
+        writeWarnLine(message) {
+          expect(message).to.match(/has added the nullish coalescing operator plugin to its build/);
+        }
+      };
+
+      expect(this.addon._addTypeScriptPlugins([
+        ['@babel/plugin-proposal-nullish-coalescing-operator']
+      ], {}).length).to.equal(3, 'plugin was not added');
+    });
+  });
+
   describe('_addDecoratorPlugins', function() {
     it('should include babel transforms by default', function() {
       expect(this.addon._addDecoratorPlugins([], {}).length).to.equal(2, 'plugins added correctly');

From 55ac0b29cf8cb5d66a0a4495b768a2b01c7c2b03 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 05:26:27 -0500
Subject: [PATCH 04/23] tests: add (failing) test for _getExtensions

---
 node-tests/addon-test.js | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 8521515e..1864c618 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -1031,6 +1031,23 @@ describe('ember-cli-babel', function() {
     });
   });
 
+  describe('_getExtensions', function() {
+    it('defaults to js only', function() {
+      expect(this.addon._getExtensions({})).to.have.members(['js']);
+    });
+    it('adds ts automatically', function() {
+      this.addon._shouldIncludeTypeScriptPlugins = function() { return true; }
+      expect(this.addon._getExtensions({})).to.have.members(['js', 'ts']);
+    });
+    it('respects user-configured extensions', function() {
+      expect(this.addon._getExtensions({ 'ember-cli-babel': { extensions: ['coffee'] } })).to.have.members(['coffee']);
+    });
+    it('respects user-configured extensions even when adding TS plugin', function() {
+      this.addon._shouldIncludeTypeScriptPlugins = function() { return true; }
+      expect(this.addon._getExtensions({ 'ember-cli-babel': { extensions: ['coffee'] } })).to.have.members(['coffee']);
+    });
+  });
+
   describe('buildBabelOptions', function() {
     this.timeout(0);
 

From 7f81c4768d98e539727c0e3937e17a48bc8ad039 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 05:27:11 -0500
Subject: [PATCH 05/23] fix: don't add ts to user-configured extensions

---
 index.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/index.js b/index.js
index e1a3962e..fd1a26cd 100644
--- a/index.js
+++ b/index.js
@@ -256,11 +256,11 @@ module.exports = {
   _getExtensions(config) {
     let shouldIncludeTypeScriptPlugins = this._shouldIncludeTypeScriptPlugins();
     let emberCLIBabelConfig = config['ember-cli-babel'] || {};
-    let extensions = emberCLIBabelConfig.extensions || ['js'];
-    if (shouldIncludeTypeScriptPlugins && !extensions.includes('ts')) {
-      extensions.push('ts');
+    let defaultExtensions = ['js'];
+    if (shouldIncludeTypeScriptPlugins) {
+      defaultExtensions.push('ts');
     }
-    return extensions;
+    return emberCLIBabelConfig.extensions || defaultExtensions;
   },
 
   _getBabelOptions(config) {

From 5a1f5a89039083af6620c7c7fd2856cffa93a5b8 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 11:13:47 -0500
Subject: [PATCH 06/23] refactor: simplify extension determination

---
 index.js | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/index.js b/index.js
index fd1a26cd..28c25b05 100644
--- a/index.js
+++ b/index.js
@@ -256,11 +256,7 @@ module.exports = {
   _getExtensions(config) {
     let shouldIncludeTypeScriptPlugins = this._shouldIncludeTypeScriptPlugins();
     let emberCLIBabelConfig = config['ember-cli-babel'] || {};
-    let defaultExtensions = ['js'];
-    if (shouldIncludeTypeScriptPlugins) {
-      defaultExtensions.push('ts');
-    }
-    return emberCLIBabelConfig.extensions || defaultExtensions;
+    return emberCLIBabelConfig.extensions || (shouldIncludeTypeScriptPlugins ? ['js', 'ts'] : ['js']);
   },
 
   _getBabelOptions(config) {

From e88eeb9e1c04b3edd390f09751ff36b0906ef8fe Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 11:23:47 -0500
Subject: [PATCH 07/23] feat: added caching of ember-cli-typescript version
 check

also s/_shouldIncludeTypeScriptPlugins/_shouldHandleTypeScript/

Co-authored-by: Dan Freeman <dfreeman@salsify.com>
---
 index.js                 | 20 +++++++++++++-------
 node-tests/addon-test.js |  4 ++--
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/index.js b/index.js
index 28c25b05..9eb2e064 100644
--- a/index.js
+++ b/index.js
@@ -254,16 +254,16 @@ module.exports = {
   },
 
   _getExtensions(config) {
-    let shouldIncludeTypeScriptPlugins = this._shouldIncludeTypeScriptPlugins();
+    let shouldHandleTypeScript = this._shouldHandleTypeScript();
     let emberCLIBabelConfig = config['ember-cli-babel'] || {};
-    return emberCLIBabelConfig.extensions || (shouldIncludeTypeScriptPlugins ? ['js', 'ts'] : ['js']);
+    return emberCLIBabelConfig.extensions || (shouldHandleTypeScript ? ['js', 'ts'] : ['js']);
   },
 
   _getBabelOptions(config) {
     let addonProvidedConfig = this._getAddonProvidedConfig(config);
     let shouldCompileModules = this._shouldCompileModules(config);
     let shouldIncludeHelpers = this._shouldIncludeHelpers(config);
-    let shouldIncludeTypeScriptPlugins = this._shouldIncludeTypeScriptPlugins();
+    let shouldHandleTypeScript = this._shouldHandleTypeScript();
     let shouldIncludeDecoratorPlugins = this._shouldIncludeDecoratorPlugins(config);
 
     let emberCLIBabelConfig = config['ember-cli-babel'];
@@ -294,7 +294,7 @@ module.exports = {
     let userPlugins = addonProvidedConfig.plugins;
     let userPostTransformPlugins = addonProvidedConfig.postTransformPlugins;
 
-    if (shouldIncludeTypeScriptPlugins) {
+    if (shouldHandleTypeScript) {
       userPlugins = this._addTypeScriptPlugins(userPlugins.slice(), addonProvidedConfig.options);
     }
 
@@ -326,10 +326,16 @@ module.exports = {
     return options;
   },
 
-  _shouldIncludeTypeScriptPlugins() {
-    let checker = new VersionChecker(this.parent).for('ember-cli-typescript', 'npm');
+  _shouldHandleTypeScript() {
+    if (this._cachedShouldHandleTypescript === undefined) {
+      // TODO: this doesn't account for things like in-repo addons and other
+      // weird inclusion structures
+      let checker = new VersionChecker(this.parent).for('ember-cli-typescript', 'npm');
 
-    return checker.gte('4.0.0-alpha');
+      this._cachedShouldHandleTypescript = checker.gte('4.0.0-alpha.0');
+    }
+
+    return this._cachedShouldHandleTypescript;
   },
 
   _shouldIncludeOptionalChainingNullishCoalescingPlugins() {
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 1864c618..b1cb8029 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -1036,14 +1036,14 @@ describe('ember-cli-babel', function() {
       expect(this.addon._getExtensions({})).to.have.members(['js']);
     });
     it('adds ts automatically', function() {
-      this.addon._shouldIncludeTypeScriptPlugins = function() { return true; }
+      this.addon._shouldHandleTypeScript = function() { return true; }
       expect(this.addon._getExtensions({})).to.have.members(['js', 'ts']);
     });
     it('respects user-configured extensions', function() {
       expect(this.addon._getExtensions({ 'ember-cli-babel': { extensions: ['coffee'] } })).to.have.members(['coffee']);
     });
     it('respects user-configured extensions even when adding TS plugin', function() {
-      this.addon._shouldIncludeTypeScriptPlugins = function() { return true; }
+      this.addon._shouldHandleTypeScript = function() { return true; }
       expect(this.addon._getExtensions({ 'ember-cli-babel': { extensions: ['coffee'] } })).to.have.members(['coffee']);
     });
   });

From b05c974ae0d970a61359c1e90edb2697fe4d6757 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 16:37:44 -0500
Subject: [PATCH 08/23] fix: conditionally apply class feature ordering
 restrictions

Co-authored-by: Dan Freeman <dfreeman@salsify.com>
---
 index.js | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/index.js b/index.js
index 9eb2e064..8388e845 100644
--- a/index.js
+++ b/index.js
@@ -344,6 +344,23 @@ module.exports = {
     return checker.gte('3.7.0');
   },
 
+	_buildClassFeaturePluginConstraints(constraints) {
+    // With older versions of ember-cli-typescript, class feature plugins like
+    // @babel/plugin-proposal-class-properties were run before the TS transform.
+    // With more recent language features like `declare` field modifiers, Babel
+    // now has assertions requiring that the TS transform runs first, so if we
+    // know we're responsible for setting that transform up, we follow those rules.
+    if (this._shouldHandleTypeScript()) {
+      constraints.after = constraints.after || [];
+      constraints.after.push('@babel/plugin-transform-typescript');
+    } else {
+      constraints.before = constraints.before || [];
+      constraints.before.push('@babel/plugin-transform-typescript');
+    }
+
+    return constraints;
+  },
+
   _addTypeScriptPlugins(plugins) {
     const { hasPlugin, addPlugin } = require('ember-cli-babel-plugin-helpers');
     const shouldIncludeOptionalChainingNullishCoalescingPlugins = this._shouldIncludeOptionalChainingNullishCoalescingPlugins();
@@ -424,10 +441,9 @@ module.exports = {
       addPlugin(
         plugins,
         [require.resolve('@babel/plugin-proposal-decorators'), { legacy: true }],
-        {
-          before: ['@babel/plugin-proposal-class-properties'],
-          after: ['@babel/plugin-transform-typescript']
-        }
+        this._buildClassFeaturePluginConstraints({
+          before: ['@babel/plugin-proposal-class-properties']
+        })
       );
     }
 
@@ -442,9 +458,9 @@ module.exports = {
       addPlugin(
         plugins,
         [require.resolve('@babel/plugin-proposal-class-properties'), { loose: options.loose || false }],
-        {
-          after: ['@babel/plugin-proposal-decorators', '@babel/plugin-transform-typescript']
-        }
+        this._buildClassFeaturePluginConstraints({
+          after: ['@babel/plugin-proposal-decorators']
+        })
       );
     }
 

From 134b0a4aa6589299b88a5f7f7e0cb82f3d0641f0 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 16:50:33 -0500
Subject: [PATCH 09/23] tests: test conditional class feature ordering
 restrictions

---
 node-tests/addon-test.js | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index b1cb8029..8c61b15e 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -845,11 +845,19 @@ describe('ember-cli-babel', function() {
       expect(loosePlugins[1][1].loose).to.equal(true, 'loose setting added correctly');
     });
 
-    it('should include class fields and decorators after typescript if detected', function() {
+    it('should include class fields and decorators after typescript if handling typescript', function() {
+      this.addon._shouldHandleTypeScript = function() { return true; }
       let plugins = this.addon._addDecoratorPlugins(['@babel/plugin-transform-typescript'], {});
       expect(plugins[0]).to.equal('@babel/plugin-transform-typescript', 'typescript still first');
       expect(plugins.length).to.equal(3, 'class fields and decorators added');
     });
+
+    it('should include class fields and decorators before typescript if not handling typescript', function() {
+      this.addon._shouldHandleTypeScript = function() { return false; }
+      let plugins = this.addon._addDecoratorPlugins(['@babel/plugin-transform-typescript'], {});
+      expect(plugins.length).to.equal(3, 'class fields and decorators added');
+      expect(plugins[2]).to.equal('@babel/plugin-transform-typescript', 'typescript is now last');
+    });
   });
 
   describe('_shouldIncludeHelpers()', function() {

From 2e79c2f876f356b9b6eabdcdfe7dfc3e3903f032 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 19 Dec 2019 16:58:29 -0500
Subject: [PATCH 10/23] fix: don't conditionally add optional chaining and
 nullish coalescing

---
 index.js                 | 61 +++++++++++++++++-----------------------
 node-tests/addon-test.js | 13 ++-------
 2 files changed, 29 insertions(+), 45 deletions(-)

diff --git a/index.js b/index.js
index 8388e845..adfddd91 100644
--- a/index.js
+++ b/index.js
@@ -338,12 +338,6 @@ module.exports = {
     return this._cachedShouldHandleTypescript;
   },
 
-  _shouldIncludeOptionalChainingNullishCoalescingPlugins() {
-    let checker = new VersionChecker(this.parent).for('typescript', 'npm');
-
-    return checker.gte('3.7.0');
-  },
-
 	_buildClassFeaturePluginConstraints(constraints) {
     // With older versions of ember-cli-typescript, class feature plugins like
     // @babel/plugin-proposal-class-properties were run before the TS transform.
@@ -363,38 +357,35 @@ module.exports = {
 
   _addTypeScriptPlugins(plugins) {
     const { hasPlugin, addPlugin } = require('ember-cli-babel-plugin-helpers');
-    const shouldIncludeOptionalChainingNullishCoalescingPlugins = this._shouldIncludeOptionalChainingNullishCoalescingPlugins();
-
-    if (shouldIncludeOptionalChainingNullishCoalescingPlugins) {
-      if (hasPlugin(plugins, '@babel/plugin-proposal-optional-chaining')) {
-        if (this.parent === this.project) {
-          this.project.ui.writeWarnLine(`${
-            this._parentName()
-          } has added the optional chaining plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 and typescript >= 3.7 are installed! You can remove the transform, or the addon that provided it.`);
-        }
-      } else {
-        addPlugin(
-          plugins,
-          [
-            require.resolve('@babel/plugin-proposal-optional-chaining'),
-          ]
-        );
+
+    if (hasPlugin(plugins, '@babel/plugin-proposal-optional-chaining')) {
+      if (this.parent === this.project) {
+        this.project.ui.writeWarnLine(`${
+          this._parentName()
+        } has added the optional chaining plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 and typescript >= 3.7 are installed! You can remove the transform, or the addon that provided it.`);
       }
+    } else {
+      addPlugin(
+        plugins,
+        [
+          require.resolve('@babel/plugin-proposal-optional-chaining'),
+        ]
+      );
+    }
 
-      if (hasPlugin(plugins, '@babel/plugin-proposal-nullish-coalescing-operator')) {
-        if (this.parent === this.project) {
-          this.project.ui.writeWarnLine(`${
-            this._parentName()
-          } has added the nullish coalescing operator plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 and typescript >= 3.7 are installed! You can remove the transform, or the addon that provided it.`);
-        }
-      } else {
-        addPlugin(
-          plugins,
-          [
-            require.resolve('@babel/plugin-proposal-nullish-coalescing-operator'),
-          ]
-        );
+    if (hasPlugin(plugins, '@babel/plugin-proposal-nullish-coalescing-operator')) {
+      if (this.parent === this.project) {
+        this.project.ui.writeWarnLine(`${
+          this._parentName()
+        } has added the nullish coalescing operator plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 and typescript >= 3.7 are installed! You can remove the transform, or the addon that provided it.`);
       }
+    } else {
+      addPlugin(
+        plugins,
+        [
+          require.resolve('@babel/plugin-proposal-nullish-coalescing-operator'),
+        ]
+      );
     }
 
     if (hasPlugin(plugins, '@babel/plugin-transform-typescript')) {
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 8c61b15e..427f32f9 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -747,8 +747,8 @@ describe('ember-cli-babel', function() {
   });
 
   describe('_addTypeScriptPlugins', function() {
-    it('should add only the TypeScript plugin by default', function() {
-      expect(this.addon._addTypeScriptPlugins([], {}).length).to.equal(1, 'plugin added correctly');
+    it('should add TypeScript, optional chaining, and nullish coalescing operator plugins', function() {
+      expect(this.addon._addTypeScriptPlugins([], {}).length).to.equal(3, 'plugins added correctly');
     });
 
     it('should warn and not add the TypeScript plugin if already added', function() {
@@ -763,16 +763,10 @@ describe('ember-cli-babel', function() {
           ['@babel/plugin-transform-typescript']
         ],
         {}
-      ).length).to.equal(1, 'plugin was not added');
-    });
-
-    it('should add optional chaining and nullish coalescing operator when told to', function() {
-      this.addon._shouldIncludeOptionalChainingNullishCoalescingPlugins = function() { return true; }
-      expect(this.addon._addTypeScriptPlugins([], {}).length).to.equal(3, 'plugins added correctly');
+      ).length).to.equal(3, 'plugin was not added');
     });
 
     it('should warn and not add optional chaining if already added', function() {
-      this.addon._shouldIncludeOptionalChainingNullishCoalescingPlugins = function() { return true; }
       this.addon.project.ui = {
         writeWarnLine(message) {
           expect(message).to.match(/has added the optional chaining plugin to its build/);
@@ -785,7 +779,6 @@ describe('ember-cli-babel', function() {
     });
 
     it('should warn and not add nullish coalescing operator if already added', function() {
-      this.addon._shouldIncludeOptionalChainingNullishCoalescingPlugins = function() { return true; }
       this.addon.project.ui = {
         writeWarnLine(message) {
           expect(message).to.match(/has added the nullish coalescing operator plugin to its build/);

From 14e75901c68fe491c3f072674509f285b99121fd Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Fri, 20 Dec 2019 13:07:59 -0500
Subject: [PATCH 11/23] refactor: get e-c-ts version from parent.addons

---
 index.js | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/index.js b/index.js
index adfddd91..0c2437b2 100644
--- a/index.js
+++ b/index.js
@@ -327,15 +327,9 @@ module.exports = {
   },
 
   _shouldHandleTypeScript() {
-    if (this._cachedShouldHandleTypescript === undefined) {
-      // TODO: this doesn't account for things like in-repo addons and other
-      // weird inclusion structures
-      let checker = new VersionChecker(this.parent).for('ember-cli-typescript', 'npm');
-
-      this._cachedShouldHandleTypescript = checker.gte('4.0.0-alpha.0');
-    }
-
-    return this._cachedShouldHandleTypescript;
+      let typeScriptAddon = this.parent.addons.find(a => a.name === 'ember-cli-typescript');
+      return typeof typeScriptAddon !== 'undefined'
+        && semver.gte(typeScriptAddon.pkg.version, '4.0.0-alpha.0');
   },
 
 	_buildClassFeaturePluginConstraints(constraints) {

From 24b8d09c07a23b0c89505d294e9060290e37eb5a Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Fri, 20 Dec 2019 13:41:53 -0500
Subject: [PATCH 12/23] tests: add test for _shouldHandleTypeScript

---
 node-tests/addon-test.js | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 427f32f9..b0068370 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -746,6 +746,30 @@ describe('ember-cli-babel', function() {
     });
   });
 
+  describe('_shouldHandleTypeScript', function() {
+    it('should return false by default', function() {
+      expect(this.addon._shouldHandleTypeScript({})).to.be.false;
+    });
+    it('should return true when ember-cli-typescript >= 4.0.0-alpha.0 is installed', function() {
+      this.addon.parent.addons.push({
+        name: 'ember-cli-typescript',
+        pkg: {
+          version: '4.0.0-alpha.0',
+        },
+      });
+      expect(this.addon._shouldHandleTypeScript({})).to.be.true;
+    });
+    it('should return false when ember-cli-typescript < 4.0.0-alpha.0 is installed', function() {
+      this.addon.parent.addons.push({
+        name: 'ember-cli-typescript',
+        pkg: {
+          version: '3.0.0',
+        },
+      });
+      expect(this.addon._shouldHandleTypeScript({})).to.be.false;
+    });
+  });
+
   describe('_addTypeScriptPlugins', function() {
     it('should add TypeScript, optional chaining, and nullish coalescing operator plugins', function() {
       expect(this.addon._addTypeScriptPlugins([], {}).length).to.equal(3, 'plugins added correctly');

From 7c6db1500b9fdd875aab8f915201dab5262e86e6 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Fri, 20 Dec 2019 14:17:48 -0500
Subject: [PATCH 13/23] feat: add  flag for manual override

---
 index.js                 | 25 +++++++++++++++----------
 node-tests/addon-test.js | 27 ++++++++++++++++++++++-----
 2 files changed, 37 insertions(+), 15 deletions(-)

diff --git a/index.js b/index.js
index 0c2437b2..0fe359f7 100644
--- a/index.js
+++ b/index.js
@@ -254,7 +254,7 @@ module.exports = {
   },
 
   _getExtensions(config) {
-    let shouldHandleTypeScript = this._shouldHandleTypeScript();
+    let shouldHandleTypeScript = this._shouldHandleTypeScript(config);
     let emberCLIBabelConfig = config['ember-cli-babel'] || {};
     return emberCLIBabelConfig.extensions || (shouldHandleTypeScript ? ['js', 'ts'] : ['js']);
   },
@@ -263,7 +263,7 @@ module.exports = {
     let addonProvidedConfig = this._getAddonProvidedConfig(config);
     let shouldCompileModules = this._shouldCompileModules(config);
     let shouldIncludeHelpers = this._shouldIncludeHelpers(config);
-    let shouldHandleTypeScript = this._shouldHandleTypeScript();
+    let shouldHandleTypeScript = this._shouldHandleTypeScript(config);
     let shouldIncludeDecoratorPlugins = this._shouldIncludeDecoratorPlugins(config);
 
     let emberCLIBabelConfig = config['ember-cli-babel'];
@@ -299,7 +299,7 @@ module.exports = {
     }
 
     if (shouldIncludeDecoratorPlugins) {
-      userPlugins = this._addDecoratorPlugins(userPlugins.slice(), addonProvidedConfig.options);
+      userPlugins = this._addDecoratorPlugins(userPlugins.slice(), addonProvidedConfig.options, config);
     }
 
     options.plugins = [].concat(
@@ -326,19 +326,24 @@ module.exports = {
     return options;
   },
 
-  _shouldHandleTypeScript() {
-      let typeScriptAddon = this.parent.addons.find(a => a.name === 'ember-cli-typescript');
+  _shouldHandleTypeScript(config) {
+      let emberCLIBabelConfig = config['ember-cli-babel'] || {};
+      if (typeof emberCLIBabelConfig.enableTypeScriptTransforms === 'boolean') {
+        return emberCLIBabelConfig.enableTypeScriptTransforms;
+      }
+      let typeScriptAddon = this.parent.addons
+        && this.parent.addons.find(a => a.name === 'ember-cli-typescript');
       return typeof typeScriptAddon !== 'undefined'
         && semver.gte(typeScriptAddon.pkg.version, '4.0.0-alpha.0');
   },
 
-	_buildClassFeaturePluginConstraints(constraints) {
+	_buildClassFeaturePluginConstraints(constraints, config) {
     // With older versions of ember-cli-typescript, class feature plugins like
     // @babel/plugin-proposal-class-properties were run before the TS transform.
     // With more recent language features like `declare` field modifiers, Babel
     // now has assertions requiring that the TS transform runs first, so if we
     // know we're responsible for setting that transform up, we follow those rules.
-    if (this._shouldHandleTypeScript()) {
+    if (this._shouldHandleTypeScript(config)) {
       constraints.after = constraints.after || [];
       constraints.after.push('@babel/plugin-transform-typescript');
     } else {
@@ -413,7 +418,7 @@ module.exports = {
     return customOptions.disableDecoratorTransforms !== true;
   },
 
-  _addDecoratorPlugins(plugins, options) {
+  _addDecoratorPlugins(plugins, options, config) {
     const { hasPlugin, addPlugin } = require('ember-cli-babel-plugin-helpers');
 
     if (hasPlugin(plugins, '@babel/plugin-proposal-decorators')) {
@@ -428,7 +433,7 @@ module.exports = {
         [require.resolve('@babel/plugin-proposal-decorators'), { legacy: true }],
         this._buildClassFeaturePluginConstraints({
           before: ['@babel/plugin-proposal-class-properties']
-        })
+        }, config)
       );
     }
 
@@ -445,7 +450,7 @@ module.exports = {
         [require.resolve('@babel/plugin-proposal-class-properties'), { loose: options.loose || false }],
         this._buildClassFeaturePluginConstraints({
           after: ['@babel/plugin-proposal-decorators']
-        })
+        }, config)
       );
     }
 
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index b0068370..b69e7516 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -768,6 +768,21 @@ describe('ember-cli-babel', function() {
       });
       expect(this.addon._shouldHandleTypeScript({})).to.be.false;
     });
+    it('should return true when TypeScript transforms are manually enabled', function() {
+      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransforms: true } })).to.be.true;
+    });
+    it('should return false when TypeScript transforms are manually disabled', function() {
+      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransforms: false } })).to.be.false;
+    });
+    it('should return false when TypeScript transforms are manually disabled, even when ember-cli-typescript >= 4.0.0-alpha.0 is installed', function() {
+      this.addon.parent.addons.push({
+        name: 'ember-cli-typescript',
+        pkg: {
+          version: '4.0.0-alpha.0',
+        },
+      });
+      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransforms: false } })).to.be.false;
+    });
   });
 
   describe('_addTypeScriptPlugins', function() {
@@ -817,7 +832,7 @@ describe('ember-cli-babel', function() {
 
   describe('_addDecoratorPlugins', function() {
     it('should include babel transforms by default', function() {
-      expect(this.addon._addDecoratorPlugins([], {}).length).to.equal(2, 'plugins added correctly');
+      expect(this.addon._addDecoratorPlugins([], {}, {}).length).to.equal(2, 'plugins added correctly');
     });
 
     it('should include only fields if it detects decorators plugin', function() {
@@ -831,6 +846,7 @@ describe('ember-cli-babel', function() {
         this.addon._addDecoratorPlugins([
           ['@babel/plugin-proposal-decorators']
         ],
+        {},
         {}
       ).length).to.equal(2, 'plugins were not added');
     });
@@ -847,31 +863,32 @@ describe('ember-cli-babel', function() {
           [
             ['@babel/plugin-proposal-class-properties']
           ],
+          {},
           {}
         ).length
       ).to.equal(2, 'plugins were not added');
     });
 
     it('should use babel options loose mode for class properties', function() {
-      let strictPlugins = this.addon._addDecoratorPlugins([], {});
+      let strictPlugins = this.addon._addDecoratorPlugins([], {}, {});
 
       expect(strictPlugins[1][1].loose).to.equal(false, 'loose is false if no option is provided');
 
-      let loosePlugins = this.addon._addDecoratorPlugins([], { loose: true });
+      let loosePlugins = this.addon._addDecoratorPlugins([], { loose: true }, {});
 
       expect(loosePlugins[1][1].loose).to.equal(true, 'loose setting added correctly');
     });
 
     it('should include class fields and decorators after typescript if handling typescript', function() {
       this.addon._shouldHandleTypeScript = function() { return true; }
-      let plugins = this.addon._addDecoratorPlugins(['@babel/plugin-transform-typescript'], {});
+      let plugins = this.addon._addDecoratorPlugins(['@babel/plugin-transform-typescript'], {}, {});
       expect(plugins[0]).to.equal('@babel/plugin-transform-typescript', 'typescript still first');
       expect(plugins.length).to.equal(3, 'class fields and decorators added');
     });
 
     it('should include class fields and decorators before typescript if not handling typescript', function() {
       this.addon._shouldHandleTypeScript = function() { return false; }
-      let plugins = this.addon._addDecoratorPlugins(['@babel/plugin-transform-typescript'], {});
+      let plugins = this.addon._addDecoratorPlugins(['@babel/plugin-transform-typescript'], {}, {});
       expect(plugins.length).to.equal(3, 'class fields and decorators added');
       expect(plugins[2]).to.equal('@babel/plugin-transform-typescript', 'typescript is now last');
     });

From ac58290139e2d0b78542a1c6d9984c5cc866e0da Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Mon, 30 Dec 2019 15:33:24 -0500
Subject: [PATCH 14/23] refactor: only enforce TS transform else case

---
 index.js | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/index.js b/index.js
index 0fe359f7..de278d15 100644
--- a/index.js
+++ b/index.js
@@ -340,13 +340,7 @@ module.exports = {
 	_buildClassFeaturePluginConstraints(constraints, config) {
     // With older versions of ember-cli-typescript, class feature plugins like
     // @babel/plugin-proposal-class-properties were run before the TS transform.
-    // With more recent language features like `declare` field modifiers, Babel
-    // now has assertions requiring that the TS transform runs first, so if we
-    // know we're responsible for setting that transform up, we follow those rules.
-    if (this._shouldHandleTypeScript(config)) {
-      constraints.after = constraints.after || [];
-      constraints.after.push('@babel/plugin-transform-typescript');
-    } else {
+    if (!this._shouldHandleTypeScript(config)) {
       constraints.before = constraints.before || [];
       constraints.before.push('@babel/plugin-transform-typescript');
     }

From 21de7961f3916b801d0a8f0eed11cafab79c7a38 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Mon, 30 Dec 2019 15:39:50 -0500
Subject: [PATCH 15/23] feat: handle ts (in addition to js) by default

---
 index.js                 |  3 +--
 node-tests/addon-test.js | 10 +---------
 2 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/index.js b/index.js
index de278d15..6bb81023 100644
--- a/index.js
+++ b/index.js
@@ -254,9 +254,8 @@ module.exports = {
   },
 
   _getExtensions(config) {
-    let shouldHandleTypeScript = this._shouldHandleTypeScript(config);
     let emberCLIBabelConfig = config['ember-cli-babel'] || {};
-    return emberCLIBabelConfig.extensions || (shouldHandleTypeScript ? ['js', 'ts'] : ['js']);
+    return emberCLIBabelConfig.extensions || ['js', 'ts'];
   },
 
   _getBabelOptions(config) {
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 1d73fc72..223462d8 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -1074,20 +1074,12 @@ describe('ember-cli-babel', function() {
   });
 
   describe('_getExtensions', function() {
-    it('defaults to js only', function() {
-      expect(this.addon._getExtensions({})).to.have.members(['js']);
-    });
-    it('adds ts automatically', function() {
-      this.addon._shouldHandleTypeScript = function() { return true; }
+    it('defaults to js and ts', function() {
       expect(this.addon._getExtensions({})).to.have.members(['js', 'ts']);
     });
     it('respects user-configured extensions', function() {
       expect(this.addon._getExtensions({ 'ember-cli-babel': { extensions: ['coffee'] } })).to.have.members(['coffee']);
     });
-    it('respects user-configured extensions even when adding TS plugin', function() {
-      this.addon._shouldHandleTypeScript = function() { return true; }
-      expect(this.addon._getExtensions({ 'ember-cli-babel': { extensions: ['coffee'] } })).to.have.members(['coffee']);
-    });
   });
 
   describe('buildBabelOptions', function() {

From 802323f8fa0379de04b92f04b934f7e7dcbc72fb Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Wed, 8 Jan 2020 07:01:43 -0500
Subject: [PATCH 16/23] chore: s/\t/ /

---
 index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/index.js b/index.js
index 6bb81023..131bec85 100644
--- a/index.js
+++ b/index.js
@@ -336,7 +336,7 @@ module.exports = {
         && semver.gte(typeScriptAddon.pkg.version, '4.0.0-alpha.0');
   },
 
-	_buildClassFeaturePluginConstraints(constraints, config) {
+  _buildClassFeaturePluginConstraints(constraints, config) {
     // With older versions of ember-cli-typescript, class feature plugins like
     // @babel/plugin-proposal-class-properties were run before the TS transform.
     if (!this._shouldHandleTypeScript(config)) {

From 5d7a817b2effa5c90ca86970f34b59662fea7892 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Wed, 8 Jan 2020 07:04:57 -0500
Subject: [PATCH 17/23] chore: add ember-cli-typescript version to comment

---
 index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/index.js b/index.js
index 131bec85..04939403 100644
--- a/index.js
+++ b/index.js
@@ -337,7 +337,7 @@ module.exports = {
   },
 
   _buildClassFeaturePluginConstraints(constraints, config) {
-    // With older versions of ember-cli-typescript, class feature plugins like
+    // With versions of ember-cli-typescript < 4.0, class feature plugins like
     // @babel/plugin-proposal-class-properties were run before the TS transform.
     if (!this._shouldHandleTypeScript(config)) {
       constraints.before = constraints.before || [];

From 5fb2aa02a0272dcf7a7722e4431dd83697c56ad3 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Wed, 8 Jan 2020 07:42:18 -0500
Subject: [PATCH 18/23] docs: document enableTypeScriptTransforms

---
 README.md | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/README.md b/README.md
index 189c6a6b..54625547 100755
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ allow you to use latest Javascript in your Ember CLI project.
     + [Enabling Source Maps](#enabling-source-maps)
     + [Modules](#modules)
     + [Disabling Debug Tooling Support](#disabling-debug-tooling-support)
+    + [Enabling TypeScript Transforms](#enabling-typescript-transforms)
   * [Addon usage](#addon-usage)
     + [Adding Custom Plugins](#adding-custom-plugins)
     + [Additional Trees](#additional-trees)
@@ -121,6 +122,7 @@ interface EmberCLIBabelConfig {
     disablePresetEnv?: boolean;
     disableEmberModulesAPIPolyfill?: boolean;
     disableDecoratorTransforms?: boolean;
+    enableTypeScriptTransforms?: boolean;
     extensions?: string[];
   };
 }
@@ -259,6 +261,40 @@ module.exports = function(defaults) {
 }
 ```
 
+#### Enabling TypeScript Transforms
+
+The transform plugins required for Babel to transpile TypeScript (including
+transforms required for all valid TypeScript features such as optional
+chaining and nullish coalescing) will automatically be enabled when
+`ember-cli-typescript` >= 4.0 is installed.
+
+You can enable the TypeScript Babel transforms manually *without*
+`ember-cli-typescript` by setting the `enableTypeScriptTransforms`to `true`.
+
+NOTE: Setting this option to `true` is not compatible with
+`ember-cli-typescript` < 4.0 because of conflicting Babel plugin ordering
+constraints and is unnecessary because `ember-cli-typescript` < 4.0 adds the
+TypeScript Babel transforms itself.
+
+NOTE: Setting this option to `true` does *not* enable type-checking. For
+integrated type-checking, you will need
+[`ember-cli-typescript`](https://ember-cli-typescript.com).
+
+In an app, manually enabling the TypeScript transforms would look like:
+
+```js
+// ember-cli-build.js
+module.exports = function(defaults) {
+  let app = new EmberApp(defaults, {
+    'ember-cli-babel': {
+      enableTypeScriptTransforms: true
+    }
+  });
+
+  return app.toTree();
+}
+```
+
 ### Addon usage
 
 #### Adding Custom Plugins

From 63932609ee71abd1441ce43553dd46e0019dca86 Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Thu, 9 Jan 2020 20:19:14 -0500
Subject: [PATCH 19/23] Revert "feat: handle ts (in addition to js) by default"

This reverts commit 21de7961f3916b801d0a8f0eed11cafab79c7a38.
---
 index.js                 |  3 ++-
 node-tests/addon-test.js | 10 +++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/index.js b/index.js
index 04939403..8d2fe42e 100644
--- a/index.js
+++ b/index.js
@@ -254,8 +254,9 @@ module.exports = {
   },
 
   _getExtensions(config) {
+    let shouldHandleTypeScript = this._shouldHandleTypeScript(config);
     let emberCLIBabelConfig = config['ember-cli-babel'] || {};
-    return emberCLIBabelConfig.extensions || ['js', 'ts'];
+    return emberCLIBabelConfig.extensions || (shouldHandleTypeScript ? ['js', 'ts'] : ['js']);
   },
 
   _getBabelOptions(config) {
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 223462d8..1d73fc72 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -1074,12 +1074,20 @@ describe('ember-cli-babel', function() {
   });
 
   describe('_getExtensions', function() {
-    it('defaults to js and ts', function() {
+    it('defaults to js only', function() {
+      expect(this.addon._getExtensions({})).to.have.members(['js']);
+    });
+    it('adds ts automatically', function() {
+      this.addon._shouldHandleTypeScript = function() { return true; }
       expect(this.addon._getExtensions({})).to.have.members(['js', 'ts']);
     });
     it('respects user-configured extensions', function() {
       expect(this.addon._getExtensions({ 'ember-cli-babel': { extensions: ['coffee'] } })).to.have.members(['coffee']);
     });
+    it('respects user-configured extensions even when adding TS plugin', function() {
+      this.addon._shouldHandleTypeScript = function() { return true; }
+      expect(this.addon._getExtensions({ 'ember-cli-babel': { extensions: ['coffee'] } })).to.have.members(['coffee']);
+    });
   });
 
   describe('buildBabelOptions', function() {

From 9bf6424154f1f1ec1004ebb5ae9821c50b2841ef Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Sat, 18 Jan 2020 10:22:54 -0500
Subject: [PATCH 20/23] fix: e-c-ts was released as 4.0.0-alpha.1

---
 index.js                 |  2 +-
 node-tests/addon-test.js | 10 +++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/index.js b/index.js
index 8d2fe42e..cc904887 100644
--- a/index.js
+++ b/index.js
@@ -334,7 +334,7 @@ module.exports = {
       let typeScriptAddon = this.parent.addons
         && this.parent.addons.find(a => a.name === 'ember-cli-typescript');
       return typeof typeScriptAddon !== 'undefined'
-        && semver.gte(typeScriptAddon.pkg.version, '4.0.0-alpha.0');
+        && semver.gte(typeScriptAddon.pkg.version, '4.0.0-alpha.1');
   },
 
   _buildClassFeaturePluginConstraints(constraints, config) {
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 1d73fc72..dbfe2108 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -750,16 +750,16 @@ describe('ember-cli-babel', function() {
     it('should return false by default', function() {
       expect(this.addon._shouldHandleTypeScript({})).to.be.false;
     });
-    it('should return true when ember-cli-typescript >= 4.0.0-alpha.0 is installed', function() {
+    it('should return true when ember-cli-typescript >= 4.0.0-alpha.1 is installed', function() {
       this.addon.parent.addons.push({
         name: 'ember-cli-typescript',
         pkg: {
-          version: '4.0.0-alpha.0',
+          version: '4.0.0-alpha.1',
         },
       });
       expect(this.addon._shouldHandleTypeScript({})).to.be.true;
     });
-    it('should return false when ember-cli-typescript < 4.0.0-alpha.0 is installed', function() {
+    it('should return false when ember-cli-typescript < 4.0.0-alpha.1 is installed', function() {
       this.addon.parent.addons.push({
         name: 'ember-cli-typescript',
         pkg: {
@@ -774,11 +774,11 @@ describe('ember-cli-babel', function() {
     it('should return false when TypeScript transforms are manually disabled', function() {
       expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransforms: false } })).to.be.false;
     });
-    it('should return false when TypeScript transforms are manually disabled, even when ember-cli-typescript >= 4.0.0-alpha.0 is installed', function() {
+    it('should return false when TypeScript transforms are manually disabled, even when ember-cli-typescript >= 4.0.0-alpha.1 is installed', function() {
       this.addon.parent.addons.push({
         name: 'ember-cli-typescript',
         pkg: {
-          version: '4.0.0-alpha.0',
+          version: '4.0.0-alpha.1',
         },
       });
       expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransforms: false } })).to.be.false;

From f6adfe19b9aa02fe0d97f09f86cf517fe2175a1d Mon Sep 17 00:00:00 2001
From: Dan Freeman <dfreeman@salsify.com>
Date: Mon, 20 Jan 2020 11:02:41 -0500
Subject: [PATCH 21/23] fix: don't emit modules for .d.ts files

---
 index.js                 | 13 +++++++++++--
 node-tests/addon-test.js | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/index.js b/index.js
index cc904887..9d78a9b1 100644
--- a/index.js
+++ b/index.js
@@ -41,7 +41,8 @@ module.exports = {
     return this._cachedDebugTree.apply(null, arguments);
   },
 
-  transpileTree(inputTree, config) {
+  transpileTree(inputTree, _config) {
+    let config = _config || this._getAddonOptions();
     let description = `000${++count}`.slice(-3);
     let postDebugTree = this._debugTree(inputTree, `${description}:input`);
 
@@ -51,7 +52,15 @@ module.exports = {
       output = postDebugTree;
     } else {
       let BabelTranspiler = require('broccoli-babel-transpiler');
-      output = new BabelTranspiler(postDebugTree, options);
+      let transpilationInput = postDebugTree;
+
+      if (this._shouldHandleTypeScript(config)) {
+        let Funnel = require('broccoli-funnel');
+        let inputWithoutDeclarations = new Funnel(transpilationInput, { exclude: ['**/*.d.ts'] });
+        transpilationInput = this._debugTree(inputWithoutDeclarations, `${description}:filtered-input`);
+      }
+
+      output = new BabelTranspiler(transpilationInput, options);
     }
 
     return this._debugTree(output, `${description}:output`);
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index dbfe2108..61c0014e 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -635,6 +635,42 @@ describe('ember-cli-babel', function() {
       }));
     });
 
+    describe('TypeScript transpilation', function() {
+      beforeEach(function() {
+        this.addon.parent.addons.push({
+          name: 'ember-cli-typescript',
+          pkg: {
+            version: '4.0.0-alpha.1'
+          }
+        });
+      });
+
+      it('should transpile .ts files', co.wrap(function*() {
+        input.write({ 'foo.ts': `let foo: string = "hi";` });
+
+        subject = this.addon.transpileTree(input.path());
+        output = createBuilder(subject);
+
+        yield output.build();
+
+        expect(
+          output.read()
+        ).to.deep.equal({
+          'foo.js': `define("foo", [], function () {\n  "use strict";\n\n  var foo = "hi";\n});`
+        });
+      }));
+
+      it('should exclude .d.ts files', co.wrap(function*() {
+        input.write({ 'foo.d.ts': `declare let foo: string;` });
+
+        subject = this.addon.transpileTree(input.path());
+        output = createBuilder(subject);
+
+        yield output.build();
+
+        expect(output.read()).to.deep.equal({});
+      }))
+    });
 
     describe('_shouldDoNothing', function() {
       it("will no-op if nothing to do", co.wrap(function* () {

From d0db857cf75745f4f256059259eff4ca6727861c Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Mon, 27 Jan 2020 16:15:31 -0500
Subject: [PATCH 22/23] chore: upgrade to latest @babel packages

---
 package.json |  6 +++---
 yarn.lock    | 55 +++++++++-------------------------------------------
 2 files changed, 12 insertions(+), 49 deletions(-)

diff --git a/package.json b/package.json
index 29ba5bc5..f945314a 100644
--- a/package.json
+++ b/package.json
@@ -43,11 +43,11 @@
     "@babel/core": "^7.8.3",
     "@babel/plugin-proposal-class-properties": "^7.8.3",
     "@babel/plugin-proposal-decorators": "^7.8.3",
-    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.7.4",
-    "@babel/plugin-proposal-optional-chaining": "^7.7.5",
+    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.8.3",
+    "@babel/plugin-proposal-optional-chaining": "^7.8.3",
     "@babel/plugin-transform-modules-amd": "^7.8.3",
     "@babel/plugin-transform-runtime": "^7.8.3",
-    "@babel/plugin-transform-typescript": "^7.7.4",
+    "@babel/plugin-transform-typescript": "^7.8.3",
     "@babel/polyfill": "^7.8.3",
     "@babel/preset-env": "^7.8.3",
     "@babel/runtime": "^7.8.3",
diff --git a/yarn.lock b/yarn.lock
index 9ddbd675..a4445663 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -84,7 +84,7 @@
     levenary "^1.1.0"
     semver "^5.5.0"
 
-"@babel/helper-create-class-features-plugin@^7.7.4", "@babel/helper-create-class-features-plugin@^7.8.3":
+"@babel/helper-create-class-features-plugin@^7.8.3":
   version "7.8.3"
   resolved "https://registry.yarnpkg.com/@babel/helper-create-class-features-plugin/-/helper-create-class-features-plugin-7.8.3.tgz#5b94be88c255f140fd2c10dd151e7f98f4bff397"
   integrity sha512-qmp4pD7zeTxsv0JNecSBsEmG1ei2MqwJq4YQcK3ZWm/0t07QstWfvuV/vm3Qt5xNMFETn2SZqpMx2MQzbtq+KA==
@@ -300,14 +300,6 @@
     "@babel/helper-plugin-utils" "^7.8.3"
     "@babel/plugin-syntax-json-strings" "^7.8.0"
 
-"@babel/plugin-proposal-nullish-coalescing-operator@^7.7.4":
-  version "7.7.4"
-  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-nullish-coalescing-operator/-/plugin-proposal-nullish-coalescing-operator-7.7.4.tgz#7db302c83bc30caa89e38fee935635ef6bd11c28"
-  integrity sha512-TbYHmr1Gl1UC7Vo2HVuj/Naci5BEGNZ0AJhzqD2Vpr6QPFWpUmBRLrIDjedzx7/CShq0bRDS2gI4FIs77VHLVQ==
-  dependencies:
-    "@babel/helper-plugin-utils" "^7.0.0"
-    "@babel/plugin-syntax-nullish-coalescing-operator" "^7.7.4"
-
 "@babel/plugin-proposal-nullish-coalescing-operator@^7.8.3":
   version "7.8.3"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-nullish-coalescing-operator/-/plugin-proposal-nullish-coalescing-operator-7.8.3.tgz#e4572253fdeed65cddeecfdab3f928afeb2fd5d2"
@@ -332,14 +324,6 @@
     "@babel/helper-plugin-utils" "^7.8.3"
     "@babel/plugin-syntax-optional-catch-binding" "^7.8.0"
 
-"@babel/plugin-proposal-optional-chaining@^7.7.5":
-  version "7.7.5"
-  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-optional-chaining/-/plugin-proposal-optional-chaining-7.7.5.tgz#f0835f044cef85b31071a924010a2a390add11d4"
-  integrity sha512-sOwFqT8JSchtJeDD+CjmWCaiFoLxY4Ps7NjvwHC/U7l4e9i5pTRNt8nDMIFSOUL+ncFbYSwruHM8WknYItWdXw==
-  dependencies:
-    "@babel/helper-plugin-utils" "^7.0.0"
-    "@babel/plugin-syntax-optional-chaining" "^7.7.4"
-
 "@babel/plugin-proposal-optional-chaining@^7.8.3":
   version "7.8.3"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-optional-chaining/-/plugin-proposal-optional-chaining-7.8.3.tgz#ae10b3214cb25f7adb1f3bc87ba42ca10b7e2543"
@@ -384,13 +368,6 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.8.0"
 
-"@babel/plugin-syntax-nullish-coalescing-operator@^7.7.4":
-  version "7.7.4"
-  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-nullish-coalescing-operator/-/plugin-syntax-nullish-coalescing-operator-7.7.4.tgz#e53b751d0c3061b1ba3089242524b65a7a9da12b"
-  integrity sha512-XKh/yIRPiQTOeBg0QJjEus5qiSKucKAiApNtO1psqG7D17xmE+X2i5ZqBEuSvo0HRuyPaKaSN/Gy+Ha9KFQolw==
-  dependencies:
-    "@babel/helper-plugin-utils" "^7.0.0"
-
 "@babel/plugin-syntax-nullish-coalescing-operator@^7.8.0":
   version "7.8.3"
   resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-nullish-coalescing-operator/-/plugin-syntax-nullish-coalescing-operator-7.8.3.tgz#167ed70368886081f74b5c36c65a88c03b66d1a9"
@@ -412,13 +389,6 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.8.0"
 
-"@babel/plugin-syntax-optional-chaining@^7.7.4":
-  version "7.7.4"
-  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-optional-chaining/-/plugin-syntax-optional-chaining-7.7.4.tgz#c91fdde6de85d2eb8906daea7b21944c3610c901"
-  integrity sha512-2MqYD5WjZSbJdUagnJvIdSfkb/ucOC9/1fRJxm7GAxY6YQLWlUvkfxoNbUPcPLHJyetKUDQ4+yyuUyAoc0HriA==
-  dependencies:
-    "@babel/helper-plugin-utils" "^7.0.0"
-
 "@babel/plugin-syntax-optional-chaining@^7.8.0":
   version "7.8.3"
   resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-optional-chaining/-/plugin-syntax-optional-chaining-7.8.3.tgz#4f69c2ab95167e0180cd5336613f8c5788f7d48a"
@@ -433,20 +403,13 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.8.3"
 
-"@babel/plugin-syntax-typescript@^7.2.0":
+"@babel/plugin-syntax-typescript@^7.2.0", "@babel/plugin-syntax-typescript@^7.8.3":
   version "7.8.3"
   resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-typescript/-/plugin-syntax-typescript-7.8.3.tgz#c1f659dda97711a569cef75275f7e15dcaa6cabc"
   integrity sha512-GO1MQ/SGGGoiEXY0e0bSpHimJvxqB7lktLLIq2pv8xG7WZ8IMEle74jIe1FhprHBWjwjZtXHkycDLZXIWM5Wfg==
   dependencies:
     "@babel/helper-plugin-utils" "^7.8.3"
 
-"@babel/plugin-syntax-typescript@^7.7.4":
-  version "7.7.4"
-  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-typescript/-/plugin-syntax-typescript-7.7.4.tgz#5d037ffa10f3b25a16f32570ebbe7a8c2efa304b"
-  integrity sha512-77blgY18Hud4NM1ggTA8xVT/dBENQf17OpiToSa2jSmEY3fWXD2jwrdVlO4kq5yzUTeF15WSQ6b4fByNvJcjpQ==
-  dependencies:
-    "@babel/helper-plugin-utils" "^7.0.0"
-
 "@babel/plugin-transform-arrow-functions@^7.8.3":
   version "7.8.3"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-arrow-functions/-/plugin-transform-arrow-functions-7.8.3.tgz#82776c2ed0cd9e1a49956daeb896024c9473b8b6"
@@ -694,14 +657,14 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.8.3"
 
-"@babel/plugin-transform-typescript@^7.7.4":
-  version "7.7.4"
-  resolved "https://registry.yarnpkg.com/@babel/plugin-transform-typescript/-/plugin-transform-typescript-7.7.4.tgz#2974fd05f4e85c695acaf497f432342de9fc0636"
-  integrity sha512-X8e3tcPEKnwwPVG+vP/vSqEShkwODOEeyQGod82qrIuidwIrfnsGn11qPM1jBLF4MqguTXXYzm58d0dY+/wdpg==
+"@babel/plugin-transform-typescript@^7.8.3":
+  version "7.8.3"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-transform-typescript/-/plugin-transform-typescript-7.8.3.tgz#be6f01a7ef423be68e65ace1f04fc407e6d88917"
+  integrity sha512-Ebj230AxcrKGZPKIp4g4TdQLrqX95TobLUWKd/CwG7X1XHUH1ZpkpFvXuXqWbtGRWb7uuEWNlrl681wsOArAdQ==
   dependencies:
-    "@babel/helper-create-class-features-plugin" "^7.7.4"
-    "@babel/helper-plugin-utils" "^7.0.0"
-    "@babel/plugin-syntax-typescript" "^7.7.4"
+    "@babel/helper-create-class-features-plugin" "^7.8.3"
+    "@babel/helper-plugin-utils" "^7.8.3"
+    "@babel/plugin-syntax-typescript" "^7.8.3"
 
 "@babel/plugin-transform-typescript@~7.4.0":
   version "7.4.5"

From 4ab55d1f44776f3579e22d655953a59f207bbacf Mon Sep 17 00:00:00 2001
From: "James C. Davis" <james@cos.io>
Date: Mon, 27 Jan 2020 16:38:26 -0500
Subject: [PATCH 23/23] refactor: don't explicitly add
 optional-chaining/nullish coalescing

As of 7.8.0, @babel/preset-env enables optional-chaining and
nullish-coalescing by default.
---
 README.md                | 22 +++++++++----------
 index.js                 | 38 ++++-----------------------------
 node-tests/addon-test.js | 46 ++++++++--------------------------------
 package.json             |  2 --
 4 files changed, 23 insertions(+), 85 deletions(-)

diff --git a/README.md b/README.md
index 54625547..ead52c7a 100755
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ allow you to use latest Javascript in your Ember CLI project.
     + [Enabling Source Maps](#enabling-source-maps)
     + [Modules](#modules)
     + [Disabling Debug Tooling Support](#disabling-debug-tooling-support)
-    + [Enabling TypeScript Transforms](#enabling-typescript-transforms)
+    + [Enabling TypeScript Transpilation](#enabling-typescript-transpilation)
   * [Addon usage](#addon-usage)
     + [Adding Custom Plugins](#adding-custom-plugins)
     + [Additional Trees](#additional-trees)
@@ -122,7 +122,7 @@ interface EmberCLIBabelConfig {
     disablePresetEnv?: boolean;
     disableEmberModulesAPIPolyfill?: boolean;
     disableDecoratorTransforms?: boolean;
-    enableTypeScriptTransforms?: boolean;
+    enableTypeScriptTransform?: boolean;
     extensions?: string[];
   };
 }
@@ -261,33 +261,31 @@ module.exports = function(defaults) {
 }
 ```
 
-#### Enabling TypeScript Transforms
+#### Enabling TypeScript Transpilation
 
-The transform plugins required for Babel to transpile TypeScript (including
-transforms required for all valid TypeScript features such as optional
-chaining and nullish coalescing) will automatically be enabled when
-`ember-cli-typescript` >= 4.0 is installed.
+The transform plugin required for Babel to transpile TypeScript will
+automatically be enabled when `ember-cli-typescript` >= 4.0 is installed.
 
-You can enable the TypeScript Babel transforms manually *without*
-`ember-cli-typescript` by setting the `enableTypeScriptTransforms`to `true`.
+You can enable the TypeScript Babel transform manually *without*
+`ember-cli-typescript` by setting the `enableTypeScriptTransform` to `true`.
 
 NOTE: Setting this option to `true` is not compatible with
 `ember-cli-typescript` < 4.0 because of conflicting Babel plugin ordering
 constraints and is unnecessary because `ember-cli-typescript` < 4.0 adds the
-TypeScript Babel transforms itself.
+TypeScript Babel transform itself.
 
 NOTE: Setting this option to `true` does *not* enable type-checking. For
 integrated type-checking, you will need
 [`ember-cli-typescript`](https://ember-cli-typescript.com).
 
-In an app, manually enabling the TypeScript transforms would look like:
+In an app, manually enabling the TypeScript transform would look like:
 
 ```js
 // ember-cli-build.js
 module.exports = function(defaults) {
   let app = new EmberApp(defaults, {
     'ember-cli-babel': {
-      enableTypeScriptTransforms: true
+      enableTypeScriptTransform: true
     }
   });
 
diff --git a/index.js b/index.js
index 9d78a9b1..2b01723f 100644
--- a/index.js
+++ b/index.js
@@ -304,7 +304,7 @@ module.exports = {
     let userPostTransformPlugins = addonProvidedConfig.postTransformPlugins;
 
     if (shouldHandleTypeScript) {
-      userPlugins = this._addTypeScriptPlugins(userPlugins.slice(), addonProvidedConfig.options);
+      userPlugins = this._addTypeScriptPlugin(userPlugins.slice(), addonProvidedConfig.options);
     }
 
     if (shouldIncludeDecoratorPlugins) {
@@ -337,8 +337,8 @@ module.exports = {
 
   _shouldHandleTypeScript(config) {
       let emberCLIBabelConfig = config['ember-cli-babel'] || {};
-      if (typeof emberCLIBabelConfig.enableTypeScriptTransforms === 'boolean') {
-        return emberCLIBabelConfig.enableTypeScriptTransforms;
+      if (typeof emberCLIBabelConfig.enableTypeScriptTransform === 'boolean') {
+        return emberCLIBabelConfig.enableTypeScriptTransform;
       }
       let typeScriptAddon = this.parent.addons
         && this.parent.addons.find(a => a.name === 'ember-cli-typescript');
@@ -357,39 +357,9 @@ module.exports = {
     return constraints;
   },
 
-  _addTypeScriptPlugins(plugins) {
+  _addTypeScriptPlugin(plugins) {
     const { hasPlugin, addPlugin } = require('ember-cli-babel-plugin-helpers');
 
-    if (hasPlugin(plugins, '@babel/plugin-proposal-optional-chaining')) {
-      if (this.parent === this.project) {
-        this.project.ui.writeWarnLine(`${
-          this._parentName()
-        } has added the optional chaining plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 and typescript >= 3.7 are installed! You can remove the transform, or the addon that provided it.`);
-      }
-    } else {
-      addPlugin(
-        plugins,
-        [
-          require.resolve('@babel/plugin-proposal-optional-chaining'),
-        ]
-      );
-    }
-
-    if (hasPlugin(plugins, '@babel/plugin-proposal-nullish-coalescing-operator')) {
-      if (this.parent === this.project) {
-        this.project.ui.writeWarnLine(`${
-          this._parentName()
-        } has added the nullish coalescing operator plugin to its build, but ember-cli-babel provides this by default now when ember-cli-typescript >= 4.0 and typescript >= 3.7 are installed! You can remove the transform, or the addon that provided it.`);
-      }
-    } else {
-      addPlugin(
-        plugins,
-        [
-          require.resolve('@babel/plugin-proposal-nullish-coalescing-operator'),
-        ]
-      );
-    }
-
     if (hasPlugin(plugins, '@babel/plugin-transform-typescript')) {
       if (this.parent === this.project) {
         this.project.ui.writeWarnLine(`${
diff --git a/node-tests/addon-test.js b/node-tests/addon-test.js
index 61c0014e..0cf54828 100644
--- a/node-tests/addon-test.js
+++ b/node-tests/addon-test.js
@@ -804,28 +804,24 @@ describe('ember-cli-babel', function() {
       });
       expect(this.addon._shouldHandleTypeScript({})).to.be.false;
     });
-    it('should return true when TypeScript transforms are manually enabled', function() {
-      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransforms: true } })).to.be.true;
+    it('should return true when the TypeScript transform is manually enabled', function() {
+      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransform: true } })).to.be.true;
     });
-    it('should return false when TypeScript transforms are manually disabled', function() {
-      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransforms: false } })).to.be.false;
+    it('should return false when the TypeScript transforms is manually disabled', function() {
+      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransform: false } })).to.be.false;
     });
-    it('should return false when TypeScript transforms are manually disabled, even when ember-cli-typescript >= 4.0.0-alpha.1 is installed', function() {
+    it('should return false when the TypeScript transform is manually disabled, even when ember-cli-typescript >= 4.0.0-alpha.1 is installed', function() {
       this.addon.parent.addons.push({
         name: 'ember-cli-typescript',
         pkg: {
           version: '4.0.0-alpha.1',
         },
       });
-      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransforms: false } })).to.be.false;
+      expect(this.addon._shouldHandleTypeScript({ 'ember-cli-babel': { enableTypeScriptTransform: false } })).to.be.false;
     });
   });
 
-  describe('_addTypeScriptPlugins', function() {
-    it('should add TypeScript, optional chaining, and nullish coalescing operator plugins', function() {
-      expect(this.addon._addTypeScriptPlugins([], {}).length).to.equal(3, 'plugins added correctly');
-    });
-
+  describe('_addTypeScriptPlugin', function() {
     it('should warn and not add the TypeScript plugin if already added', function() {
       this.addon.project.ui = {
         writeWarnLine(message) {
@@ -834,35 +830,11 @@ describe('ember-cli-babel', function() {
       };
 
       expect(
-        this.addon._addTypeScriptPlugins([
+        this.addon._addTypeScriptPlugin([
           ['@babel/plugin-transform-typescript']
         ],
         {}
-      ).length).to.equal(3, 'plugin was not added');
-    });
-
-    it('should warn and not add optional chaining if already added', function() {
-      this.addon.project.ui = {
-        writeWarnLine(message) {
-          expect(message).to.match(/has added the optional chaining plugin to its build/);
-        }
-      };
-
-      expect(this.addon._addTypeScriptPlugins([
-        ['@babel/plugin-proposal-optional-chaining']
-      ], {}).length).to.equal(3, 'plugin was not added');
-    });
-
-    it('should warn and not add nullish coalescing operator if already added', function() {
-      this.addon.project.ui = {
-        writeWarnLine(message) {
-          expect(message).to.match(/has added the nullish coalescing operator plugin to its build/);
-        }
-      };
-
-      expect(this.addon._addTypeScriptPlugins([
-        ['@babel/plugin-proposal-nullish-coalescing-operator']
-      ], {}).length).to.equal(3, 'plugin was not added');
+      ).length).to.equal(1, 'plugin was not added');
     });
   });
 
diff --git a/package.json b/package.json
index f945314a..896bcd28 100644
--- a/package.json
+++ b/package.json
@@ -43,8 +43,6 @@
     "@babel/core": "^7.8.3",
     "@babel/plugin-proposal-class-properties": "^7.8.3",
     "@babel/plugin-proposal-decorators": "^7.8.3",
-    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.8.3",
-    "@babel/plugin-proposal-optional-chaining": "^7.8.3",
     "@babel/plugin-transform-modules-amd": "^7.8.3",
     "@babel/plugin-transform-runtime": "^7.8.3",
     "@babel/plugin-transform-typescript": "^7.8.3",