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angular-docs-cn/aio/content/guide/updating-to-version-12.md

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Updating Angular

This guide contains information related to updating to Angular version 12.

Updating CLI applications

For step-by-step instructions on how to update to the latest Angular release and leverage our automated migration tools to do so, use the interactive update guide at update.angular.io.

Building applications with Ivy

For libraries, View Engine is deprecated and will be removed in version 13. New libraries created with version 12 or later default to Ivy. For more information about distributing libraries with View Engine and Ivy, see the Building libraries with Ivy section of Creating libraries.

Changes and deprecations in version 12

For information about Angular's deprecation and removal practices, see Angular Release Practices.

  • Applications can no longer build with View Engine by setting enableIvy: false. Support for building libraries with View Engine, for backwards compatibility, is deprecated and will be removed in Angular version 13. New libraries created with Angular version 12 will default to building and distributing with Ivy. For more information, see Creating Libraries.
  • The Ivy-based IDE language service is now on by default. See PR #1279.
  • Angular's View Engine-based algorithm for generating i18n message IDs is deprecated. Angular version 12 adds a new flag to localize-extract called --migrateMapFile which generates a JSON file that can be used to map legacy message IDs to canonical ones. There is also a new script called localize-migrate that can use the mapping file which localize-extract generates and migrate all of the IDs in the files that are passed in. For better stability, if you are using Angular's i18n, run this migration to move to the new message ID generation algorithm. If you don't run this migration, all your generated message IDs will change when Angular removes the View Engine compiler. See PR #41026.
  • There is now a new build option named inlineStyleLanguage for defining the style sheet language in inline component styles. Currently supported language options are CSS (default), Sass, SCSS, and LESS. The default of CSS enables existing projects to continue to function as expected. See PR #20514.
  • For new applications, strict mode is now the default in the CLI. See PR #20029.
  • Add emitEvent option for AbstractControl class methods. See PR #31031.
  • Support APP_INITIALIZER to work with observables. See PR #31031.
  • HttpClient supports specifying request metadata. See PR #25751.

{@a breaking-changes}

Breaking changes in Angular version 12

  • Add support for TypeScript 4.2. TypeScript <4.2.3 is no longer supported. The supported range of TypeScript versions is 4.2.3 to 4.2.x. See PR #41158.
  • Angular CDK and Angular Material internally now use the new Sass module system, which is actively maintained by the Sass team at Google. Consequently, applications can no longer consume Angular CDK/Material's Sass with the node-sass npm package. node-sass is unmaintained and does not support newer Sass features. Instead, applications must use the sass npm package, or the sass-embedded npm package for the sass-embedded beta.
  • The Angular tooling now uses Webpack 5 to build applications. Webpack 4 usage and support has been removed. You don't need to make any project level configuration changes to use the upgraded Webpack version when using the official Angular builders. Custom builders based on this package that use the experimental programmatic APIs may need to be updated to become compatible with Webpack 5. See PR #20466.
  • Webpack 5 generates similar but differently named files for lazy-loaded JavaScript files in development configurations when the namedChunks option is enabled. For the majority of users this change should have no effect on the application or build process. Production builds should also not be affected as the namedChunks option is disabled by default in production configurations. However, if a project's post-build process makes assumptions as to the file names, then adjustments may need to be made to account for the new naming paradigm. Such post-build processes could include custom file transformations after the build, integration into service-side frameworks, or deployment procedures. An example of a development file name change is lazy-lazy-module.js becoming src_app_lazy_lazy_module_ts.js. See PR #20466.
  • Webpack 5 now includes web worker support. However, the structure of the URL within the worker constructor must be in a specific format that differs from the current requirement. To update web worker usage, where ./app.worker is the actual worker name, change new Worker('./app.worker', ...) to new Worker(new URL('./app.worker', import.meta.url), ...). See PR #20466.
  • Critical CSS inlining is now enabled by default. To turn this off, set inlineCritical to false. See PR #20096 and the Style preprocessor options section of Angular workspace configuration.
  • ng build now produces production bundle by default. See PR #20128.
  • Previously, the Forms module ignored min and max attributes defined on the <input type="number">. Now these attributes trigger min and max validation logic in cases where formControl, formControlName, or ngModel directives are also present on a given input. See PR #39063.

{@a deprecations}

New deprecations

  • Support for Internet Explorer 11 is deprecated. See Deprecated APIs and features and Microsoft 365 apps say farewell to Internet Explorer 11 and Windows 10 sunsets Microsoft Edge Legacy.
  • Sass imports from @angular/material/theming are deprecated. There is a new Angular Material Sass API for @use. Run the migration script ng g @angular/material:themingApi to switch all your Sass imports for Angular CDK and Angular Material to the new API and @use.
  • Support for publishing libraries with View Engine has been deprecated:
    • You can now compile libraries in partial compilation mode to generate Ivy compatible output that will be linked when an application using that library is bundled.
    • New libraries you create with the Angular CLI default to partial compilation mode, and do not support View Engine. You can still build a library with View Engine. See Creating libraries for more information.
    • Libraries compiled in partial compilation mode will not contain legacy i18n message IDs. If the library was previously compiled by View Engine, and contained legacy i18n message IDs, then applications may have translation files that you'll need to migrate to the new message ID format. For more information, see Migrating legacy localization IDs.
    • For context, see Issue #38366.

Since version 9, Angular Ivy is the default rendering engine. For more information about Ivy, see Angular Ivy.