Add support for npm overrides

README.md

@@ -143,6 +143,14 @@ module.exports = async function() {
           devDependencies: {
             'ember-source': '2.11.0'
           },
+          /*
+            You can optionally define npm overrides to enforce a  specific dependency version
+            to be installed. This is useful if other libraries you depend on include different
+            versions of a package. This does nothing if `useYarn` is true;
+          */
+          overrides: {
+            'lodash': '5.0.0'
+          }
           /*
             When `useYarn` is true, you can optionally define yarn resolutions to enforce a
             specific dependency version to be installed. This is useful if other libraries

lib/dependency-manager-adapters/npm.js

@@ -178,6 +178,8 @@ module.exports = CoreObject.extend({
 
     if (this.useYarnCommand) {
       this._overridePackageJSONDependencies(packageJSON, depSet, 'resolutions');
+    } else {
+      this._overridePackageJSONDependencies(packageJSON, depSet, 'overrides');
     }
 
     return packageJSON;

test/dependency-manager-adapters/npm-adapter-test.js

@@ -536,6 +536,75 @@ describe('npmAdapter', () => {
       expect(resultJSON.resolutions).to.be.undefined;
     });
 
+    it('adds a override for the specified dependency version', () => {
+      let npmAdapter = new NpmAdapter({
+        cwd: tmpdir,
+      });
+      let packageJSON = {
+        dependencies: { 'ember-cli-babel': '5.0.0' },
+      };
+      let depSet = {
+        dependencies: { 'ember-cli-babel': '6.0.0' },
+        overrides: { 'ember-cli-babel': '6.0.0' },
+      };
+
+      let resultJSON = npmAdapter._packageJSONForDependencySet(packageJSON, depSet);
+
+      expect(resultJSON.overrides['ember-cli-babel']).to.equal('6.0.0');
+    });
+
+    it('removes a dependency from overrides if its version is null', () => {
+      let npmAdapter = new NpmAdapter({
+        cwd: tmpdir,
+      });
+      let packageJSON = {
+        dependencies: { 'ember-cli-babel': '5.0.0' },
+        overrides: { 'ember-cli-babel': '5.0.0' },
+      };
+      let depSet = {
+        dependencies: { 'ember-cli-babel': '6.0.0' },
+        overrides: { 'ember-cli-babel': null },
+      };
+
+      let resultJSON = npmAdapter._packageJSONForDependencySet(packageJSON, depSet);
+
+      expect(resultJSON.overrides['ember-cli-babel']).to.be.undefined;
+    });
+
+    it('doesnt add overrides if there are none specified', () => {
+      let npmAdapter = new NpmAdapter({
+        cwd: tmpdir,
+      });
+      let packageJSON = {
+        dependencies: { 'ember-cli-babel': '5.0.0' },
+      };
+      let depSet = {
+        dependencies: { 'ember-cli-babel': '6.0.0' },
+      };
+
+      let resultJSON = npmAdapter._packageJSONForDependencySet(packageJSON, depSet);
+
+      expect(resultJSON.resolutions).to.be.undefined;
+    });
+
+    it('doesnt add overrides when using yarn', () => {
+      let npmAdapter = new NpmAdapter({
+        cwd: tmpdir,
+        useYarnCommand: true,
+      });
+      let packageJSON = {
+        dependencies: { 'ember-cli-babel': '5.0.0' },
+      };
+      let depSet = {
+        dependencies: { 'ember-cli-babel': '6.0.0' },
+        overrides: { 'ember-cli-babel': '6.0.0' },
+      };
+
+      let resultJSON = npmAdapter._packageJSONForDependencySet(packageJSON, depSet);
+
+      expect(resultJSON.overrides).to.be.undefined;
+    });
+
     it('changes specified npm dev dependency versions', () => {
       let npmAdapter = new NpmAdapter({ cwd: tmpdir });
       let packageJSON = {