feat: modify source files before compilation

Ability to modify source files before compilation.
E.g.: might be used to compile pug files to html.
Probably related to ng-packagr#1619.
NgPackage config can have resourceReader string - path to exported JS
function responsible for reading sources code files.

closes ng-packagr#1601

src/lib/ng-package/package.ts

@@ -61,6 +61,11 @@ export class NgPackage {
  return path.join(this.basePath, this.primary.$get('dest'));
  }
 
+ /** Absolute path of the package's resource reader function. */
+ public get resourceReader(): string {
+ return path.join(this.basePath, this.primary.$get('resourceReader'));
+ }
+
  public get keepLifecycleScripts(): boolean {
  return this.primary.$get('keepLifecycleScripts');
  }

src/lib/ngc/compile-source-files.ts

@@ -23,7 +23,6 @@ export async function compileSourceFiles(
  const tsConfigOptions: CompilerOptions = { ...tsConfig.options, ...extraOptions };
  const entryPoint: EntryPointNode = graph.find(isEntryPointInProgress());
  const ngPackageNode: PackageNode = graph.find(isPackage);
- const inlineStyleLanguage = ngPackageNode.data.inlineStyleLanguage;
 
  const tsCompilerHost = ngccTransformCompilerHost(
  cacheCompilerHost(
@@ -32,7 +31,7 @@ export async function compileSourceFiles(
  tsConfigOptions,
  moduleResolutionCache,
  stylesheetProcessor,
- inlineStyleLanguage,
+ ngPackageNode.data,
  ),
  tsConfigOptions,
  ngccProcessor,

src/lib/ts/cache-compiler-host.ts

@@ -3,11 +3,11 @@ import type { CompilerHost, CompilerOptions } from '@angular/compiler-cli';
 import { createHash } from 'crypto';
 import * as path from 'path';
 import ts from 'typescript';
-import { NgPackageConfig } from '../../ng-package.schema';
 import { FileCache } from '../file-system/file-cache';
 import { BuildGraph } from '../graph/build-graph';
 import { Node } from '../graph/node';
 import { EntryPointNode, fileUrl } from '../ng-package/nodes';
+import { NgPackage } from '../ng-package/package';
 import { StylesheetProcessor } from '../styles/stylesheet-processor';
 import { ensureUnixPath } from '../utils/path';
 
@@ -17,7 +17,7 @@ export function cacheCompilerHost(
  compilerOptions: CompilerOptions,
  moduleResolutionCache: ts.ModuleResolutionCache,
  stylesheetProcessor?: StylesheetProcessor,
- inlineStyleLanguage?: NgPackageConfig['inlineStyleLanguage'],
+ ngPackage?: NgPackage,
  sourcesFileCache: FileCache = entryPoint.cache.sourcesFileCache,
 ): CompilerHost {
  const compilerHost = ts.createIncrementalCompilerHost(compilerOptions);
@@ -127,15 +127,21 @@ export function cacheCompilerHost(
 
  const cache = sourcesFileCache.getOrCreate(fileName);
  if (cache.content === undefined) {
- if (/(?:html?|svg)$/.test(path.extname(fileName))) {
- // template
- cache.content = compilerHost.readFile.call(this, fileName);
+ if (ngPackage?.resourceReader) {
+ const resourceReaderPath = path.relative(__dirname, ngPackage.resourceReader).replace(/\\/g, '/');
+ const resourceReaderFn = await import(resourceReaderPath);
+ cache.content = resourceReaderFn.default(fileName, compilerHost, stylesheetProcessor);
  } else {
- // stylesheet
- cache.content = await stylesheetProcessor.process({
- filePath: fileName,
- content: compilerHost.readFile.call(this, fileName),
- });
+ if (/(?:html?|svg)$/.test(path.extname(fileName))) {
+ // template
+ cache.content = compilerHost.readFile.call(this, fileName);
+ } else {
+ // stylesheet
+ cache.content = await stylesheetProcessor.process({
+ filePath: fileName,
+ content: compilerHost.readFile.call(this, fileName),
+ });
+ }
  }
 
  if (cache.content === undefined) {
@@ -152,9 +158,9 @@ export function cacheCompilerHost(
  return null;
  }
 
- if (inlineStyleLanguage) {
+ if (ngPackage?.inlineStyleLanguage) {
  const key = createHash('sha1').update(data).digest('hex');
- const fileName = `${context.containingFile}-${key}.${inlineStyleLanguage}`;
+ const fileName = `${context.containingFile}-${key}.${ngPackage.inlineStyleLanguage}`;
  const cache = sourcesFileCache.getOrCreate(fileName);
  if (cache.content === undefined) {
  cache.content = await stylesheetProcessor.process({

src/ng-package.schema.json

@@ -18,6 +18,10 @@
  "type": "string",
  "default": "dist"
  },
+ "resourceReader": {
+ "description": "Path to the resource reader function, that could be used to transform source files before compilation.",
+ "type": "string"
+ },
  "keepLifecycleScripts": {
  "description": "Enable this to keep the 'scripts' section in package.json. Read the NPM Blog on 'Package install scripts vulnerability' – http://blog.npmjs.org/post/141702881055/package-install-scripts-vulnerability",
  "type": "boolean",