angular/angular-cli · error · Error

Compilation output path cannot be empty.

Error message

Compilation output path cannot be empty.

What it means

The ServiceWorkerPlugin's apply() augments the built app with a service worker after compilation. It reads the output path from compilation.outputOptions.path (not build options) because localization may redirect output to a temp directory. If that path is empty/undefined, the plugin cannot locate the output to augment, so it throws.

Source

Thrown at packages/angular_devkit/build_angular/src/tools/webpack/plugins/service-worker-plugin.ts:38

  constructor(private readonly options: ServiceWorkerPluginOptions) {}

  apply(compiler: Compiler) {
    compiler.hooks.done.tapPromise('angular-service-worker', async (stats) => {
      if (stats.hasErrors()) {
        // Don't generate a service worker if the compilation has errors.
        // When there are errors some files will not be emitted which would cause other errors down the line such as readdir failures.
        return;
      }

      const { projectRoot, root, baseHref = '', ngswConfigPath } = this.options;
      const { compilation } = stats;
      // We use the output path from the compilation instead of build options since during
      // localization the output path is modified to a temp directory.
      // See: https://github.com/angular/angular-cli/blob/7e64b1537d54fadb650559214fbb12707324cd75/packages/angular_devkit/build_angular/src/utils/i18n-options.ts#L251-L252
      const outputPath = compilation.outputOptions.path;

      if (!outputPath) {
        throw new Error('Compilation output path cannot be empty.');
      }

      try {
        await augmentAppWithServiceWorker(
          projectRoot,
          root,
          outputPath,
          baseHref,
          ngswConfigPath,
          // eslint-disable-next-line @typescript-eslint/no-explicit-any
          (compiler.inputFileSystem as any).promises,
          // eslint-disable-next-line @typescript-eslint/no-explicit-any
          (compiler.outputFileSystem as any).promises,
        );
      } catch (error) {
        compilation.errors.push(
          new compilation.compiler.webpack.WebpackError(
            `Failed to generate service worker - ${error instanceof Error ? error.message : error}`,

View on GitHub (pinned to bb72145f9a)

Solutions

1. Ensure `outputPath` in your build options is set and non-empty.
2. Remove any custom webpack configuration that overrides or empties `output.path`.
3. Disable the service worker (`serviceWorker: false` or remove ngswConfigPath) if building in an environment without a real output path (e.g. dev-server).
4. Upgrade Angular CLI; later versions handle dev-server/service-worker combinations differently.

Example fix

// before (angular.json)
"options": { "serviceWorker": true, "ngswConfigPath": "ngsw-config.json" }
// after (when using dev-server / no outputPath)
"configurations": { "development": { "serviceWorker": false } }

const outputPath = compilation.outputOptions.path;
if (!outputPath) throw new Error('Cannot enable service worker: compilation output path is empty.');

function hasOutputPath(o: webpack.Compilation['outputOptions']): o is typeof o & { path: string } {
  return typeof o.path === 'string' && o.path.length > 0;
}

try {
  await runBuild();
} catch (err) {
  if (err instanceof Error && err.message === 'Compilation output path cannot be empty.') {
    logger.error('Service worker enabled but no output path set; check outputPath/output.path in your config.');
  } else throw err;
}

When it happens

Trigger: Running a build with service worker enabled (ngswConfigPath set) while the webpack compilation's outputOptions.path is empty — e.g. an misconfigured output path, dev-server in-memory output without a path, or a custom webpack config overriding output.

Common situations: Custom webpack configs that clear/override `output.path`; running via dev-server with service worker enabled where output is memory-only; programmatic use of the builder without a valid output path; localization builds where the temp output path setup failed.

Related errors

• Webpack Dev Server configuration was not set.
• No options were specified to "postcss-cli-resources".
• Invalid Webpack stats configuration.
• Multiple bundles have been named the same: '${duplicates.joi
• Webpack configuration file ${configPath} does not exist.

AI-assisted analysis of angular/angular-cli@bb72145f9a (2026-08-30). Data as JSON: /api/errors/7d96029eb498746e. Report an issue: GitHub.