{"record":{"id":"c3caba673a33a25d","repo":"angular/angular-cli","slug":"this-build-is-using-the-application-builder-but-tr","errorCode":null,"errorMessage":"This build is using the application builder but transforms.webpackConfiguration was provided. The transform will be ignored.","messagePattern":"This build is using the application builder but transforms\\.webpackConfiguration was provided\\. The transform will be ignored\\.","errorType":"console","errorClass":null,"httpStatus":null,"severity":"warning","filePath":"packages/angular_devkit/build_angular/src/builders/karma/index.ts","lineNumber":52,"sourceCode":"  options: KarmaBuilderOptions,\n  context: BuilderContext,\n  transforms: {\n    webpackConfiguration?: ExecutionTransformer<Configuration>;\n    // The karma options transform cannot be async without a refactor of the builder implementation\n    karmaOptions?: (options: KarmaConfigOptions) => KarmaConfigOptions;\n  } = {},\n): AsyncIterable<BuilderOutput> {\n  context.logger.warn(\n    'The \"@angular-devkit/build-angular:karma\" builder is deprecated as part of Angular\\'s Webpack support deprecation. ' +\n      'Use \"@angular/build:karma\" instead. For more information, see https://angular.dev/tools/cli/build-system-migration.',\n  );\n\n  // Check Angular version.\n  assertCompatibleAngularVersion(context.workspaceRoot);\n\n  if (await checkForEsbuild(options, context)) {\n    if (transforms.webpackConfiguration) {\n      context.logger.warn(\n        `This build is using the application builder but transforms.webpackConfiguration was provided. The transform will be ignored.`,\n      );\n    }\n\n    if (options.fileReplacements) {\n      options.fileReplacements = normalizeFileReplacements(options.fileReplacements, './');\n    }\n\n    if (typeof options.polyfills === 'string') {\n      options.polyfills = [options.polyfills];\n    }\n\n    const { executeKarmaBuilder } = await import('@angular/build');\n\n    yield* executeKarmaBuilder(\n      options as unknown as import('@angular/build').KarmaBuilderOptions,\n      context,\n      transforms,","sourceCodeStart":34,"sourceCodeEnd":70,"githubUrl":"https://github.com/angular/angular-cli/blob/bb72145f9ab45aee29f523236b3a25cd0813a841/packages/angular_devkit/build_angular/src/builders/karma/index.ts#L34-L70","documentation":"When the karma builder detects it is running through the esbuild-based application builder (checkForEsbuild), a provided transforms.webpackConfiguration cannot be applied because no webpack configuration exists; the builder warns that the transform is ignored.","triggerScenarios":"Executing the karma builder with a webpackConfiguration execution transform (via createBuilder harness or API) while the project resolves to the esbuild/application builder path.","commonSituations":"Programmatic builder usage that customizes webpack config (e.g., in tests or custom tooling) after migrating karma to the application builder; transform silently does nothing.","solutions":["Remove the transforms.webpackConfiguration from your builder invocation since it has no effect.","Migrate karma customization to options supported by @angular/build:karma (e.g., karmaOptions).","If webpack customization is essential, stay on the webpack-based builder (accepting deprecation)."],"exampleFix":"// before\nexecute(options, context, { webpackConfiguration: (c) => ({ ...c, devtool: 'eval' }) })\n// after\nexecute(options, context, { karmaOptions: { reporters: ['dots'] } })","handlingStrategy":"validation","validationCode":"// Only pass webpackConfiguration transforms when NOT using the application builder:\nconst useEsbuild = await checkForEsbuild(options, context);\nconst transforms = useEsbuild ? { karmaOptions } : { karmaOptions, webpackConfiguration };","typeGuard":null,"tryCatchPattern":null,"preventionTips":["After migrating to @angular/build:karma, delete webpackConfiguration transforms from custom tooling.","Verify transforms actually take effect by asserting on the resulting config in tests.","Treat 'transform will be ignored' warnings as silent behavior changes, fix immediately."],"tags":["angular","esbuild","webpack","karma"],"backgroundTag":"ignored-webpack-transform","analyzedSha":"bb72145f9ab45aee29f523236b3a25cd0813a841","analyzedAt":"2026-08-30T02:47:34.745Z","schemaVersion":2},"datasetVersion":"2026-08-30T03:17:51.788Z"}