feat(@ngtools/webpack): reuse compiler host in webpack child compilations

Author: filipesilva

packages/ngtools/webpack/src/angular_compiler_plugin.ts

@@ -596,7 +596,7 @@ export class AngularCompilerPlugin {
 
  // Registration hook for webpack plugin.
  // tslint:disable-next-line:no-big-function
- apply(compiler: Compiler & { watchMode?: boolean }) {
+ apply(compiler: Compiler & { watchMode?: boolean, parentCompilation?: compilation.Compilation }) {
  // The below is require by NGCC processor
  // since we need to know which fields we need to process
  compiler.hooks.environment.tap('angular-compiler', () => {
@@ -610,8 +610,14 @@ export class AngularCompilerPlugin {
  // cleanup if not watching
  compiler.hooks.thisCompilation.tap('angular-compiler', compilation => {
  compilation.hooks.finishModules.tap('angular-compiler', () => {
+ let rootCompiler = compiler;
+ while (rootCompiler.parentCompilation) {
+ // tslint:disable-next-line:no-any
+ rootCompiler = compiler.parentCompilation as any;
+ }
+
  // only present for webpack 4.23.0+, assume true otherwise
- const watchMode = compiler.watchMode === undefined ? true : compiler.watchMode;
+ const watchMode = rootCompiler.watchMode === undefined ? true : rootCompiler.watchMode;
  if (!watchMode) {
  this._program = null;
  this._transformers = [];
@@ -859,6 +865,22 @@ export class AngularCompilerPlugin {
  throw new Error('An @ngtools/webpack plugin already exist for this compilation.');
  }
 
+ // If there is no compiler host at this point, it means that the environment hook did not run.
+ // This happens in child compilations that inherit the parent compilation file system.
+ if (this._compilerHost === undefined) {
+ const inputFs = compilation.compiler.inputFileSystem as VirtualFileSystemDecorator;
+ if (!inputFs.getWebpackCompilerHost) {
+ throw new Error('AngularCompilerPlugin is running in a child compilation, but could' +
+ 'not find a WebpackCompilerHost in the parent compilation.');
+ }
+
+ // Use the existing WebpackCompilerHost to ensure builds and rebuilds work.
+ this._compilerHost = createCompilerHost({
+ options: this._compilerOptions,
+ tsHost: inputFs.getWebpackCompilerHost(),
+ }) as CompilerHost & WebpackCompilerHost;
+ }
+
  // Set a private variable for this plugin instance.
  // tslint:disable-next-line:no-any
  (compilation as any)._ngToolsWebpackPluginInstance = this;

packages/ngtools/webpack/src/virtual_file_system_decorator.ts

@@ -21,6 +21,10 @@ export class VirtualFileSystemDecorator implements InputFileSystem {
  private _webpackCompilerHost: WebpackCompilerHost,
  ) { }
 
+ getWebpackCompilerHost() {
+ return this._webpackCompilerHost;
+ }
+
  getVirtualFilesPaths() {
  return this._webpackCompilerHost.getNgFactoryPaths();
  }