feat(@angular-devkit/build-optimizer): don't use getImportTslibTransformer

This transformer can cause size regressions when it introduces `tslib` imports across independent chunks.

It should be deprecated because tslib adoption has become more ubiquitous.

Should also speed up Build Optimizer processing time because there's one less thing to do.

Author: filipesilva

packages/angular_devkit/build_optimizer/src/build-optimizer/build-optimizer.ts

@@ -11,7 +11,6 @@ import {
   TransformJavascriptOutput,
   transformJavascript,
 } from '../helpers/transform-javascript';
-import { getImportTslibTransformer, testImportTslib } from '../transforms/import-tslib';
 import { getPrefixClassesTransformer, testPrefixClasses } from '../transforms/prefix-classes';
 import { getPrefixFunctionsTransformer } from '../transforms/prefix-functions';
 import {
@@ -109,8 +108,6 @@ export function buildOptimizer(options: BuildOptimizerOptions): TransformJavascr
     selectedGetScrubFileTransformer = getScrubFileTransformerForCore;
   }
 
-  const isWebpackBundle = content.indexOf('__webpack_require__') !== -1;
-
   // Determine which transforms to apply.
   const getTransforms = [];
 
@@ -133,22 +130,10 @@ export function buildOptimizer(options: BuildOptimizerOptions): TransformJavascr
     typeCheck = true;
   }
 
-  // tests are not needed for fast path
-  // usage will be expanded once transformers are verified safe
-  const ignoreTest = !options.emitSourceMap && !typeCheck;
-
   if (testPrefixClasses(content)) {
     getTransforms.unshift(getPrefixClassesTransformer);
   }
 
-  // This transform introduces import/require() calls, but this won't work properly on libraries
-  // built with Webpack. These libraries use __webpack_require__() calls instead, which will break
-  // with a new import that wasn't part of it's original module list.
-  // We ignore this transform for such libraries.
-  if (!isWebpackBundle && (ignoreTest || testImportTslib(content))) {
-    getTransforms.unshift(getImportTslibTransformer);
-  }
-
   getTransforms.push(getWrapEnumsTransformer);
 
   const transformJavascriptOpts: TransformJavascriptOptions = {

packages/angular_devkit/build_optimizer/src/build-optimizer/build-optimizer_spec.ts

@@ -22,11 +22,6 @@ describe('build-optimizer', () => {
     it('applies scrub-file and prefix-functions to side-effect free modules', () => {
       const input = tags.stripIndent`
         ${imports}
-        var __extends = (this && this.__extends) || function (d, b) {
-            for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
-            function __() { this.constructor = d; }
-            d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
-        };
         var ChangeDetectionStrategy;
         (function (ChangeDetectionStrategy) {
           ChangeDetectionStrategy[ChangeDetectionStrategy["OnPush"] = 0] = "OnPush";
@@ -55,7 +50,6 @@ describe('build-optimizer', () => {
         var RenderType_MdOption = ɵcrt({ encapsulation: 2, styles: styles_MdOption});
       `;
       const output = tags.oneLine`
-        import { __extends } from "tslib";
         ${imports}
         var ChangeDetectionStrategy = /*@__PURE__*/ (function (ChangeDetectionStrategy) {
           ChangeDetectionStrategy[ChangeDetectionStrategy["OnPush"] = 0] = "OnPush";

packages/angular_devkit/build_optimizer/src/transforms/import-tslib.ts

@@ -17,6 +17,9 @@ export function testImportTslib(content: string) {
   return regex.test(content);
 }
 
+/**
+ * @deprecated From 0.9.0
+ */
 export function getImportTslibTransformer(): ts.TransformerFactory<ts.SourceFile> {
   return (context: ts.TransformationContext): ts.Transformer<ts.SourceFile> => {