chore(broccoli): implement diffing LodashRenderer plugin

Closes #2438

tools/broccoli/broccoli-lodash.ts

@@ -0,0 +1,45 @@
+import fs = require('fs');
+import fse = require('fs-extra');
+import path = require('path');
+var _ = require('lodash');
+import {wrapDiffingPlugin, DiffingBroccoliPlugin, DiffResult} from './diffing-broccoli-plugin';
+
+interface LodashRendererOptions {
+  encoding?: string;
+  context?: any;
+  // files option unsupported --- use Funnel on inputTree instead.
+  files?: string[];
+}
+
+const kDefaultOptions: LodashRendererOptions = {encoding: 'utf-8', context: {}, files: []};
+
+
+/**
+ * Intercepts each changed file and replaces its contents with
+ * the associated changes.
+ */
+export class LodashRenderer implements DiffingBroccoliPlugin {
+  constructor(private inputPath, private cachePath,
+              private options: LodashRendererOptions = kDefaultOptions) {}
+
+  rebuild(treeDiff: DiffResult) {
+    let{encoding = 'utf-8', context = {}} = this.options;
+    let processFile = (relativePath) => {
+      let sourceFilePath = path.join(this.inputPath, relativePath);
+      let destFilePath = path.join(this.cachePath, relativePath);
+      let content = fs.readFileSync(sourceFilePath, {encoding});
+      let transformedContent = _.template(content)(context);
+      fse.outputFileSync(destFilePath, transformedContent);
+    };
+
+    let removeFile = (relativePath) => {
+      let destFilePath = path.join(this.cachePath, relativePath);
+      fs.unlinkSync(destFilePath);
+    };
+
+    treeDiff.changedPaths.forEach(processFile);
+    treeDiff.removedPaths.forEach(removeFile);
+  }
+}
+
+export default wrapDiffingPlugin(LodashRenderer);

tools/broccoli/trees/dart_tree.ts

@@ -7,7 +7,7 @@ import destCopy from '../broccoli-dest-copy';
 var Funnel = require('broccoli-funnel');
 import mergeTrees from '../broccoli-merge-trees';
 var path = require('path');
-var renderLodashTemplate = require('broccoli-lodash');
+import renderLodashTemplate from '../broccoli-lodash';
 var stew = require('broccoli-stew');
 import ts2dart from '../broccoli-ts2dart';
 import dartfmt from '../broccoli-dartfmt';
@@ -124,13 +124,9 @@ function getTemplatedPubspecsTree() {
     }
   };
   // Generate pubspec.yaml from templates.
-  // Lodash insists on dropping one level of extension, so first artificially rename the yaml
-  // files to .yaml.template.
-  var pubspecs = stew.rename(modulesFunnel(['**/pubspec.yaml']), '.yaml', '.yaml.template');
+  var pubspecs = modulesFunnel(['**/pubspec.yaml']);
   // Then render the templates.
-  return renderLodashTemplate(
-      pubspecs,
-      {files: ['**/pubspec.yaml.template'], context: {'packageJson': COMMON_PACKAGE_JSON}});
+  return renderLodashTemplate(pubspecs, {context: {'packageJson': COMMON_PACKAGE_JSON}});
 }
 
 function getDocsTree() {

tools/broccoli/trees/node_tree.ts

@@ -6,7 +6,7 @@ import transpileWithTraceur from '../traceur/index';
 var Funnel = require('broccoli-funnel');
 import mergeTrees from '../broccoli-merge-trees';
 var path = require('path');
-var renderLodashTemplate = require('broccoli-lodash');
+import renderLodashTemplate from '../broccoli-lodash';
 import replace from '../broccoli-replace';
 var stew = require('broccoli-stew');
 
@@ -73,11 +73,9 @@ module.exports = function makeNodeTree(destinationPath) {
     }
   };
 
-  // Add a .template extension since renderLodashTemplate strips one extension
-  var packageJsons = stew.rename(new Funnel(modulesTree, {include: ['**/package.json']}), '.json',
-                                 '.json.template');
-  packageJsons = renderLodashTemplate(
-      packageJsons, {files: ["**/**"], context: {'packageJson': COMMON_PACKAGE_JSON}});
+  var packageJsons = new Funnel(modulesTree, {include: ['**/package.json']});
+  packageJsons =
+      renderLodashTemplate(packageJsons, {context: {'packageJson': COMMON_PACKAGE_JSON}});
 
   // HACK: workaround for Traceur behavior.
   // It expects all transpiled modules to contain this marker.