feat(@ngtools/webpack): prevent build failure in case of custom locale,review changes

Author: rahulbhooteshwar

packages/@ngtools/webpack/src/angular_compiler_plugin.ts

@@ -111,7 +111,7 @@ export class AngularCompilerPlugin {
   // Webpack plugin.
   private _firstRun = true;
   private _donePromise: Promise<void> | null;
-  private _normalizedLocale: string;
+  private _normalizedLocale: string | null;
   private _warnings: (string | Error)[] = [];
   private _errors: (string | Error)[] = [];
 
@@ -1038,7 +1038,7 @@ export class AngularCompilerPlugin {
     return { program, emitResult, diagnostics: allDiagnostics };
   }
 
-  private _validateLocale(locale: string) {
+  private _validateLocale(locale: string): string | null {
     // Get the path of the common module.
     const commonPath = path.dirname(require.resolve('@angular/common/package.json'));
     // Check if the locale file exists
@@ -1065,11 +1065,12 @@ export class AngularCompilerPlugin {
         if (locales.indexOf(parentLocale) !== -1) {
           locale = parentLocale;
         } else {
-          console.log(`Unable to load the locale data file "@angular/common/locales/${locale}", ` +
+          this._warnings.push(`AngularCompilerPlugin: Unable to load the locale data file ` +
+            `"@angular/common/locales/${locale}", ` +
             `please check that "${locale}" is a valid locale id.
             Proceeding with default locale data registration i.e. 'en'.
             If needed, localeData can be registered against custom locale in application module.`);
-          locale = 'en';
+          return null;
         }
       }
     }