refactor(@angular-devkit/build-angular): support reading i18n project options

Author: clydin

packages/angular_devkit/build_angular/src/browser/index.ts

@@ -64,6 +64,7 @@ import {
   normalizeOptimization,
   normalizeSourceMaps,
 } from '../utils';
+import { I18nOptions, createI18nOptions } from '../utils/i18n-options';
 import { manglingDisabled } from '../utils/mangle-options';
 import {
   CacheKey,
@@ -167,13 +168,23 @@ async function initialize(
   context: BuilderContext,
   host: virtualFs.Host<fs.Stats>,
   webpackConfigurationTransform?: ExecutionTransformer<webpack.Configuration>,
-): Promise<{ config: webpack.Configuration[]; projectRoot: string; projectSourceRoot?: string }> {
+): Promise<{
+  config: webpack.Configuration[];
+  projectRoot: string;
+  projectSourceRoot?: string;
+  i18n: I18nOptions;
+}> {
   const { config, projectRoot, projectSourceRoot } = await buildBrowserWebpackConfigFromContext(
     options,
     context,
     host,
   );
 
+  // target is verified in the above call
+  // tslint:disable-next-line: no-non-null-assertion
+  const metadata = await context.getProjectMetadata(context.target!);
+  const i18n = createI18nOptions(metadata);
+
   let transformedConfig;
   if (webpackConfigurationTransform) {
     transformedConfig = [];
@@ -190,7 +201,7 @@ async function initialize(
     ).toPromise();
   }
 
-  return { config: transformedConfig || config, projectRoot, projectSourceRoot };
+  return { config: transformedConfig || config, projectRoot, projectSourceRoot, i18n };
 }
 
 // tslint:disable-next-line: no-big-function
@@ -211,7 +222,7 @@ export function buildWebpackBrowser(
 
   return from(initialize(options, context, host, transforms.webpackConfiguration)).pipe(
     // tslint:disable-next-line: no-big-function
-    switchMap(({ config: configs, projectRoot }) => {
+    switchMap(({ config: configs, projectRoot, i18n }) => {
       const tsConfig = readTsconfig(options.tsConfig, context.workspaceRoot);
       const target = tsConfig.options.target || ScriptTarget.ES5;
       const buildBrowserFeatures = new BuildBrowserFeatures(projectRoot, target);
@@ -591,7 +602,7 @@ export function buildWebpackBrowser(
                     ? workerFile
                     : require.resolve('../utils/process-bundle-bootstrap'),
                   'process',
-                  { cachePath: cacheDownlevelPath },
+                  { cachePath: cacheDownlevelPath, i18n },
                 );
 
                 try {

packages/angular_devkit/build_angular/src/utils/i18n-options.ts

@@ -0,0 +1,47 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+import { json } from '@angular-devkit/core';
+
+export interface I18nOptions {
+  sourceLocale?: string;
+  locales: Record<string, { file: string; translation: unknown }>;
+}
+
+export function createI18nOptions(metadata: json.JsonObject): I18nOptions {
+  const i18n: I18nOptions = { locales: {} };
+
+  if (metadata.sourceLocale !== undefined && typeof metadata.sourceLocale !== 'string') {
+    throw new Error('Project i18n sourceLocale field is malformed. Expected a string.');
+  }
+
+  // en-US is the default locale added to Angular applications (https://angular.io/guide/i18n#i18n-pipes)
+  i18n.sourceLocale = metadata.sourceLocale || 'en-US';
+
+  if (
+    metadata.locales !== undefined &&
+    (!metadata.locales || typeof metadata.locales !== 'object' || Array.isArray(metadata.locales))
+  ) {
+    throw new Error('Project i18n locales field is malformed. Expected an object.');
+  } else if (metadata.locales) {
+    for (const [locale, translationFile] of Object.entries(metadata.locales)) {
+      if (typeof translationFile !== 'string') {
+        throw new Error(
+          `Project i18n locales field value for '${locale}' is malformed. Expected a string.`,
+        );
+      }
+
+      // TODO: Integrate translation file parsing from FW when available
+      i18n.locales[locale] = {
+        file: translationFile,
+        translation: {},
+      };
+    }
+  }
+
+  return i18n;
+}