Angular compiler options

When you use ahead-of-time compilation (AOT), you can control how your application is compiled by specifying template compiler options in the TypeScript configuration file.

The template options object, angularCompilerOptions, is a sibling to the compilerOptions object that supplies standard options to the TypeScript compiler.

{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    // ...
  },
  "angularCompilerOptions": {
    "enableI18nLegacyMessageIdFormat": false,
    "strictInjectionParameters": true,
    // ...
  }
}

Configuration inheritance with extends

Like the TypeScript compiler, the Angular AOT compiler also supports extends in the angularCompilerOptions section of the TypeScript configuration file. The extends property is at the top level, parallel to compilerOptions and angularCompilerOptions.

A TypeScript configuration can inherit settings from another file using the extends property. The configuration options from the base file are loaded first, then overridden by those in the inheriting configuration file.

For example:

{
    "extends": "./tsconfig.json",
    "compilerOptions": {
      "outDir": "./out-tsc/app",
    // ...
    "angularCompilerOptions": {
      "strictTemplates": true,
      "preserveWhitespaces": true,
      // ...
    }
  }

For more information, see the TypeScript Handbook.

Template options

The following options are available for configuring the AOT template compiler.

annotationsAs

Modifies how Angular-specific annotations are emitted to improve tree-shaking. Non-Angular annotations are not affected. One of static fields or decorators. The default value is static fields.

• By default, the compiler replaces decorators with a static field in the class, which allows advanced tree-shakers like Closure compiler to remove unused classes

• The decorators value leaves the decorators in place, which makes compilation faster. TypeScript emits calls to the __decorate helper. Use --emitDecoratorMetadata for runtime reflection.

  NOTE: That the resulting code cannot tree-shake properly.

annotateForClosureCompiler

When true, use Tsickle to annotate the emitted JavaScript with JSDoc comments needed by the Closure Compiler. Default is false.

compilationMode

Specifies the compilation mode to use. The following modes are available:

Modes	Details
'full'	Generates fully AOT-compiled code according to the version of Angular that is currently being used.
'partial'	Generates code in a stable, but intermediate form suitable for a published library.

The default value is 'full'.

disableExpressionLowering

When true, the default, transforms code that is or could be used in an annotation, to allow it to be imported from template factory modules. See metadata rewriting for more information.

When false, disables this rewriting, requiring the rewriting to be done manually.

disableTypeScriptVersionCheck

When true, the compiler does not look at the TypeScript version and does not report an error when an unsupported version of TypeScript is used. Not recommended, as unsupported versions of TypeScript might have undefined behavior. Default is false.

enableI18nLegacyMessageIdFormat

Instructs the Angular template compiler to create legacy ids for messages that are tagged in templates by the i18n attribute. See Mark text for translations for more information about marking messages for localization.

Set this option to false unless your project relies upon translations that were created earlier using legacy IDs. Default is true.

The pre-Ivy message extraction tooling created a variety of legacy formats for extracted message IDs. These message formats have some issues, such as whitespace handling and reliance upon information inside the original HTML of a template.

The new message format is more resilient to whitespace changes, is the same across all translation file formats, and can be created directly from calls to $localize. This allows $localize messages in application code to use the same ID as identical i18n messages in component templates.

enableResourceInlining

When true, replaces the templateUrl and styleUrls properties in all @Component decorators with inline content in the template and styles properties.

When enabled, the .js output of ngc does not include any lazy-loaded template or style URLs.

For library projects created with the Angular CLI, the development configuration default is true.

enableLegacyTemplate

When true, enables the deprecated <template> element in place of <ng-template>. Default is false. Might be required by some third-party Angular libraries.

flatModuleId

The module ID to use for importing a flat module (when flatModuleOutFile is true). References created by the template compiler use this module name when importing symbols from the flat module. Ignored if flatModuleOutFile is false.

flatModuleOutFile

When true, generates a flat module index of the given filename and the corresponding flat module metadata. Use to create flat modules that are packaged similarly to @angular/core and @angular/common. When this option is used, the package.json for the library should refer to the created flat module index instead of the library index file.

Produces only one .metadata.json file, which contains all the metadata necessary for symbols exported from the library index. In the created .ngfactory.js files, the flat module index is used to import symbols. Symbols that include both the public API from the library index as well as shrouded internal symbols.

By default the .ts file supplied in the files field is assumed to be the library index. If more than one .ts file is specified, libraryIndex is used to select the file to use. If more than one .ts file is supplied without a libraryIndex, an error is produced.

A flat module index .d.ts and .js is created with the given flatModuleOutFile name in the same location as the library index .d.ts file.

For example, if a library uses the public_api.ts file as the library index of the module, the tsconfig.json files field would be ["public_api.ts"]. The flatModuleOutFile option could then be set, for example, to "index.js", which produces index.d.ts and index.metadata.json files. The module field of the library's package.json would be "index.js" and the typings field would be "index.d.ts".

fullTemplateTypeCheck

When true, the recommended value, enables the binding expression validation phase of the template compiler. This phase uses TypeScript to verify binding expressions. For more information, see Template type checking.

Default is false, but when you use the Angular CLI command ng new --strict, it is set to true in the new project's configuration.

The fullTemplateTypeCheck option has been deprecated in Angular 13 in favor of the strictTemplates family of compiler options.

generateCodeForLibraries

When true, creates factory files (.ngfactory.js and .ngstyle.js) for .d.ts files with a corresponding .metadata.json file. The default value is true.

When false, factory files are created only for .ts files. Do this when using factory summaries.

preserveWhitespaces

When false, the default, removes blank text nodes from compiled templates, which results in smaller emitted template factory modules. Set to true to preserve blank text nodes.

When using hydration, it is recommended that you use preserveWhitespaces: false, which is the default value. If you choose to enable preserving whitespaces by adding preserveWhitespaces: true to your tsconfig, it is possible you may encounter issues with hydration. This is not yet a fully supported configuration. Ensure this is also consistently set between the server and client tsconfig files. See the hydration guide for more details.

skipMetadataEmit

When true, does not produce .metadata.json files. Default is false.

The .metadata.json files contain information needed by the template compiler from a .ts file that is not included in the .d.ts file produced by the TypeScript compiler. This information includes, for example, the content of annotations, such as a component's template, which TypeScript emits to the .js file but not to the .d.ts file.

You can set to true when using factory summaries, because the factory summaries include a copy of the information that is in the .metadata.json file.

Set to true if you are using TypeScript's --outFile option, because the metadata files are not valid for this style of TypeScript output. The Angular community does not recommend using --outFile with Angular. Use a bundler, such as webpack, instead.

skipTemplateCodegen

When true, does not emit .ngfactory.js and .ngstyle.js files. This turns off most of the template compiler and disables the reporting of template diagnostics.

Can be used to instruct the template compiler to produce .metadata.json files for distribution with an npm package. This avoids the production of .ngfactory.js and .ngstyle.js files that cannot be distributed to npm.

For library projects created with the Angular CLI, the development configuration default is true.

strictMetadataEmit

When true, reports an error to the .metadata.json file if "skipMetadataEmit" is false. Default is false. Use only when "skipMetadataEmit" is false and "skipTemplateCodegen" is true.

This option is intended to verify the .metadata.json files emitted for bundling with an npm package. The validation is strict and can emit errors for metadata that would never produce an error when used by the template compiler. You can choose to suppress the error emitted by this option for an exported symbol by including @dynamic in the comment documenting the symbol.

It is valid for .metadata.json files to contain errors. The template compiler reports these errors if the metadata is used to determine the contents of an annotation. The metadata collector cannot predict the symbols that are designed for use in an annotation. It preemptively includes error nodes in the metadata for the exported symbols. The template compiler can then use the error nodes to report an error if these symbols are used.

If the client of a library intends to use a symbol in an annotation, the template compiler does not normally report this. It gets reported after the client actually uses the symbol. This option allows detection of these errors during the build phase of the library and is used, for example, in producing Angular libraries themselves.

For library projects created with the Angular CLI, the development configuration default is true.

strictInjectionParameters

When true, reports an error for a supplied parameter whose injection type cannot be determined. When false, constructor parameters of classes marked with @Injectable whose type cannot be resolved produce a warning. The recommended value is true, but the default value is false.

When you use the Angular CLI command ng new --strict, it is set to true in the created project's configuration.

strictTemplates

When true, enables strict template type checking.

The strictness flags that this option enables allow you to turn on and off specific types of strict template type checking. See troubleshooting template errors.

When you use the Angular CLI command ng new --strict, it is set to true in the new project's configuration.

trace

When true, prints extra information while compiling templates. Default is false.

Command line options

Most of the time you interact with the Angular Compiler indirectly using Angular CLI. When debugging certain issues, you might find it useful to invoke the Angular Compiler directly. You can use the ngc command provided by the @angular/compiler-cli npm package to call the compiler from the command line.

The ngc command is just a wrapper around TypeScript's tsc compiler command and is primarily configured via the tsconfig.json configuration options documented in the previous sections.

Besides the configuration file, you can also use tsc command line options to configure ngc.