From fe6ee945d4e5bf42673cf7d50f16a4a5e8b6a93b Mon Sep 17 00:00:00 2001
From: Logan Smyth <loganfsmyth@gmail.com>
Date: Thu, 27 Sep 2018 11:07:41 -0700
Subject: [PATCH] Upgrade the source-map module for WASM performance.

---
 .travis.yml                                   |  2 +-
 packages/devtools-source-map/assets.js        |  3 +-
 packages/devtools-source-map/package.json     |  2 +-
 .../devtools-source-map/src/source-map.js     | 29 +++++++++++++++----
 .../src/utils/wasmAssetBrowser.js             |  6 ++++
 yarn.lock                                     |  4 +++
 6 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 2c43c321b3..7491c8e953 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,7 +13,7 @@ env:
   global:
     - DISPLAY=':99.0'
     - YARN_VERSION='1.9.4'
-    - MC_COMMIT='156f9442db84' # https://hg.mozilla.org/mozilla-central/shortlog
+    - MC_COMMIT='13b0256be449' # https://hg.mozilla.org/mozilla-central/shortlog
 
 notifications:
   slack:
diff --git a/packages/devtools-source-map/assets.js b/packages/devtools-source-map/assets.js
index 7454b042b0..a911626402 100644
--- a/packages/devtools-source-map/assets.js
+++ b/packages/devtools-source-map/assets.js
@@ -4,5 +4,6 @@
 // @flow
 
 module.exports = {
-  "dwarf_to_json.wasm": require.resolve("./wasm/dwarf_to_json.wasm")
+  "dwarf_to_json.wasm": require.resolve("./wasm/dwarf_to_json.wasm"),
+  "source-map-mappings.wasm": require.resolve("source-map/lib/mappings.wasm")
 };
diff --git a/packages/devtools-source-map/package.json b/packages/devtools-source-map/package.json
index 19c4f1b567..bd1a55df13 100644
--- a/packages/devtools-source-map/package.json
+++ b/packages/devtools-source-map/package.json
@@ -22,6 +22,6 @@
     "devtools-utils": "0.0.14",
     "md5": "^2.2.1",
     "regenerator-runtime": "^0.10.3",
-    "source-map": "^0.6.1"
+    "source-map": "^0.7.3"
   }
 }
diff --git a/packages/devtools-source-map/src/source-map.js b/packages/devtools-source-map/src/source-map.js
index 27dfcd92f4..ea33d388dd 100644
--- a/packages/devtools-source-map/src/source-map.js
+++ b/packages/devtools-source-map/src/source-map.js
@@ -171,17 +171,36 @@ async function getGeneratedLocation(
     return location;
   }
 
-  const { line, column } = map.generatedPositionFor({
+  const positions = map.allGeneratedPositionsFor({
     source: originalSource.url,
     line: location.line,
-    column: location.column == null ? 0 : location.column,
-    bias: SourceMapConsumer.LEAST_UPPER_BOUND
+    column: location.column == null ? 0 : location.column
   });
 
+  // Prior to source-map 0.7, the source-map module returned the earliest
+  // generated location in the file when there were multiple generated
+  // locations. The current comparison fn in 0.7 does not appear to take
+  // generated location into account properly.
+  let match;
+  for (const pos of positions) {
+    if (!match || pos.line < match.line || pos.column < match.column) {
+      match = pos;
+    }
+  }
+
+  if (!match) {
+    match = map.generatedPositionFor({
+      source: originalSource.url,
+      line: location.line,
+      column: location.column == null ? 0 : location.column,
+      bias: SourceMapConsumer.LEAST_UPPER_BOUND
+    });
+  }
+
   return {
     sourceId: generatedSourceId,
-    line,
-    column
+    line: match.line,
+    column: match.column
   };
 }
 
diff --git a/packages/devtools-source-map/src/utils/wasmAssetBrowser.js b/packages/devtools-source-map/src/utils/wasmAssetBrowser.js
index 21331f3dba..e123c278bd 100644
--- a/packages/devtools-source-map/src/utils/wasmAssetBrowser.js
+++ b/packages/devtools-source-map/src/utils/wasmAssetBrowser.js
@@ -3,10 +3,16 @@
  * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
 // @flow
 
+const { SourceMapConsumer } = require("source-map");
+
 let root;
 function setAssetRootURL(assetRoot: string): void {
   // Remove any trailing slash so we don't generate a double-slash below.
   root = assetRoot.replace(/\/$/, "");
+
+  SourceMapConsumer.initialize({
+    "lib/mappings.wasm": `${root}/source-map-mappings.wasm`
+  });
 }
 
 async function getDwarfToWasmData(name: string): Promise<ArrayBuffer> {
diff --git a/yarn.lock b/yarn.lock
index 97038e477a..4de0e8993d 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -11025,6 +11025,10 @@ source-map@^0.6.0, source-map@^0.6.1, source-map@~0.6.1:
   version "0.6.1"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
 
+source-map@^0.7.3:
+  version "0.7.3"
+  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.7.3.tgz#5302f8169031735226544092e64981f751750383"
+
 space-separated-tokens@^1.0.0:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/space-separated-tokens/-/space-separated-tokens-1.1.2.tgz#e95ab9d19ae841e200808cd96bc7bd0adbbb3412"