title: An unhandled exception occurred: The development server only supports localizing a single locale per build
body: <p>Please advise how this error can be fixed, I'm trying to implement localization but having this issue.
  Guide I used: <a href="https://angular.io/guide/i18n#merge-translations-into-the-app" rel="nofollow noreferrer">https://angular.io/guide/i18n#merge-translations-into-the-app</a>
  If it will help, I was able to run using ng serve --configuration=ru --open and app was localized, but after I used _build.bat it broke my app and I cannot run it anymore at all.
  If I specify different port it throws an error &quot;NGCC failed&quot;.
  Here's example of my code from angular.json file:</p>
  <pre><code>&quot;projects&quot;: {
  &quot;operator&quot;: {
     &quot;i18n&quot;: {
          &quot;sourceLocale&quot;: &quot;en-US&quot;,
          &quot;locales&quot;: {
            &quot;ru&quot;: &quot;src/locale/messages.ru.xlf&quot;
          }
     },
    &quot;projectType&quot;: &quot;application&quot;,
    &quot;schematics&quot;: {},
    &quot;root&quot;: &quot;&quot;,
    &quot;sourceRoot&quot;: &quot;src&quot;,
    &quot;prefix&quot;: &quot;app&quot;,
    &quot;architect&quot;: {
      &quot;build&quot;: {
        &quot;builder&quot;: &quot;@angular-devkit/build-angular:browser&quot;,
        &quot;options&quot;: {
          &quot;outputPath&quot;: &quot;dist/operator&quot;,
          &quot;index&quot;: &quot;src/index.html&quot;,
          &quot;main&quot;: &quot;src/main.ts&quot;,
          &quot;polyfills&quot;: &quot;src/polyfills.ts&quot;,
          &quot;tsConfig&quot;: &quot;tsconfig.app.json&quot;,
          &quot;aot&quot;: true,
          &quot;localize&quot;: true,
          &quot;assets&quot;: [
            &quot;src/favicon.ico&quot;,
            &quot;src/assets&quot;
          ],
          &quot;styles&quot;: [
            &quot;src/styles.css&quot;
          ],
          &quot;scripts&quot;: [&quot;src/version.js&quot;]
        },
        &quot;configurations&quot;: {
          &quot;ru&quot;: {
              &quot;localize&quot;: [&quot;ru&quot;]
          },
          &quot;production&quot;: {
            &quot;fileReplacements&quot;: [
              {
                &quot;replace&quot;: &quot;src/environments/environment.ts&quot;,
                &quot;with&quot;: &quot;src/environments/environment.prod.ts&quot;
              }
            ],
            &quot;optimization&quot;: true,
            &quot;outputHashing&quot;: &quot;all&quot;,
            &quot;sourceMap&quot;: false,
            &quot;extractCss&quot;: true,
            &quot;namedChunks&quot;: false,
            &quot;extractLicenses&quot;: true,
            &quot;vendorChunk&quot;: false,
            &quot;buildOptimizer&quot;: true,
            &quot;budgets&quot;: [
              {
                &quot;type&quot;: &quot;initial&quot;,
                &quot;maximumWarning&quot;: &quot;3mb&quot;,
                &quot;maximumError&quot;: &quot;5mb&quot;
              },
              {
                &quot;type&quot;: &quot;anyComponentStyle&quot;,
                &quot;maximumWarning&quot;: &quot;6kb&quot;,
                &quot;maximumError&quot;: &quot;10kb&quot;
              }
            ]
          }
        }
      },
      &quot;serve&quot;: {
        &quot;builder&quot;: &quot;@angular-devkit/build-angular:dev-server&quot;,
        &quot;options&quot;: {
          &quot;browserTarget&quot;: &quot;operator:build&quot;
        },
        &quot;configurations&quot;: {
          &quot;production&quot;: {
            &quot;browserTarget&quot;: &quot;operator:build:production&quot;
          },
          &quot;ru&quot;: {
              &quot;browserTarget&quot;: &quot;operator:build:ru&quot;
          }
        }
      }
  </code></pre>