build: remove duplicate licenses in bundles (#5195)

* No longer includes the license comments from every source file in the different FESM and UMD bundles.
* Build packages are now emitted with explicit `LF` line endings instead of platform dependent line endings.

tools/package-tools/build-bundles.ts

@@ -1,5 +1,5 @@
 import {join} from 'path';
-import {ScriptTarget, ModuleKind} from 'typescript';
+import {ScriptTarget, ModuleKind, NewLineKind} from 'typescript';
 import {uglifyJsFile} from './minify-sources';
 import {createRollupBundle} from './rollup-helpers';
 import {remapSourcemap} from './sourcemap-remap';
@@ -38,7 +38,8 @@ export async function buildPackageBundles(entryFile: string, packageName: string
     importHelpers: true,
     target: ScriptTarget.ES5,
     module: ModuleKind.ES2015,
-    allowJs: true
+    allowJs: true,
+    newLine: NewLineKind.LineFeed
   });
 
   await remapSourcemap(fesm2014File);

tools/package-tools/rollup-helpers.ts

@@ -1,4 +1,5 @@
 import {buildConfig} from './build-config';
+import {rollupRemoveLicensesPlugin} from './rollup-remove-licenses';
 
 // There are no type definitions available for these imports.
 const rollup = require('rollup');
@@ -59,10 +60,11 @@ export type BundleConfig = {
 
 /** Creates a rollup bundle of a specified JavaScript file.*/
 export function createRollupBundle(config: BundleConfig): Promise<any> {
-  const bundleOptions: any = {
+  const bundleOptions = {
     context: 'this',
     external: Object.keys(ROLLUP_GLOBALS),
     entry: config.entry,
+    plugins: [rollupRemoveLicensesPlugin]
   };
 
   const writeOptions = {
@@ -79,7 +81,7 @@ export function createRollupBundle(config: BundleConfig): Promise<any> {
   // When creating a UMD, we want to exclude tslib from the `external` bundle option so that it
   // is inlined into the bundle.
   if (config.format === 'umd') {
-    bundleOptions.plugins = [rollupNodeResolutionPlugin()];
+    bundleOptions.plugins.push(rollupNodeResolutionPlugin());
 
     const external = Object.keys(ROLLUP_GLOBALS);
     external.splice(external.indexOf('tslib'), 1);

tools/package-tools/rollup-remove-licenses.ts

@@ -0,0 +1,26 @@
+import {buildConfig} from './build-config';
+import MagicString from 'magic-string';
+
+/** License banner from the build config that will be removed in all source files. */
+const licenseBanner = buildConfig.licenseBanner;
+
+/**
+ * Rollup plugin that removes all license banners of source files.
+ * This is necessary to avoid having the license comment repeated in the output.
+ */
+export const rollupRemoveLicensesPlugin = {
+  name: 'rollup-clean-duplicate-licenses',
+  transform: (code: string) => {
+    const newContent = new MagicString(code);
+
+    // Walks through every occurrence of a license comment and overwrites it with an empty string.
+    for (let pos = -1; (pos = code.indexOf(licenseBanner, pos + 1)) !== -1; null) {
+      newContent.overwrite(pos, pos + licenseBanner.length, '');
+    }
+
+    return {
+      code: newContent.toString(),
+      map:  newContent.generateMap({ hires: true })
+    };
+  }
+};