Respect babel retainLines option.

README.md

@@ -82,6 +82,7 @@ interface EmberCLIBabelConfig {
     exclude?: string[];
     useBuiltIns?: boolean;
     sourceMaps?: boolean | "inline" | "both";
+    retainLines?: boolean;
     plugins?: BabelPlugin[];
   };
 
@@ -171,6 +172,22 @@ let app = new EmberApp(defaults, {
 });
 ```
 
+#### Enabling Retain Lines
+
+Babel generated source maps will enable you to debug your original ES6 source code. This is disabled by default because this will lead to wacky code but is handy for scenarios where you can't use source maps or breakpoints in external debugger are offset (vscode has this issue, see the extension https://github.com/Microsoft/vscode-chrome-debug)
+
+To enable it, pass `retainLines: true` in your `babel` options.
+
+```js
+// ember-cli-build.js
+
+var app = new EmberApp(defaults, {
+  babel: {
+    retainLines: true
+  }
+});
+```
+
 #### Modules
 
 Older versions of Ember CLI (`< 2.12`) use its own ES6 module transpiler.

index.js

@@ -204,10 +204,16 @@ module.exports = {
       sourceMaps = config.babel.sourceMaps;
     }
 
+    let retainLines = false;
+    if (config.babel && "retainLines" in config.babel) {
+      retainLines = config.babel.retainLines;
+    }
+
     let options = {
       annotation: providedAnnotation || `Babel: ${this._parentName()}`,
       sourceMaps,
-      throwUnlessParallelizable
+      throwUnlessParallelizable,
+      retainLines
     };
 
     let userPlugins = addonProvidedConfig.plugins;

node-tests/addon-test.js

@@ -722,6 +722,13 @@ describe('ember-cli-babel', function() {
       expect(result.sourceMaps).to.equal('inline');
     });
 
+    it("uses provided retainLines if specified", function() {
+      let options = { babel: { retainLines: true } };
+
+      let result = this.addon.buildBabelOptions(options);
+      expect(result.retainLines).to.equal(true);
+    });
+
     it('does not include all provided options', function() {
       let babelOptions = { blah: true };
       let options = {