angular-docs-cn/packages/localize/init/index.ts

/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import {$localize, _global, LocalizeFn} from '../src/localize';

export {$localize, LocalizeFn, TranslateFn} from '../src/localize';

// Attach $localize to the global context, as a side-effect of this module.
_global.$localize = $localize;

// `declare global` allows us to escape the current module and place types on the global namespace
declare global {
  /**
   * Tag a template literal string for localization.
   *
   * For example:
   *
   * ```ts
   * $localize `some string to localize`
   * ```
   *
   * **Providing meaning, description and id**
   *
   * You can optionally specify one or more of `meaning`, `description` and `id` for a localized
   * string by pre-pending it with a colon delimited block of the form:
   *
   * ```ts
   * $localize`:meaning|description@@id:source message text`;
   *
   * $localize`:meaning|:source message text`;
   * $localize`:description:source message text`;
   * $localize`:@@id:source message text`;
   * ```
   *
   * This format is the same as that used for `i18n` markers in Angular templates. See the
   * [Angular 18n guide](guide/i18n#mark-text-for-translations).
   *
   * **Naming placeholders**
   *
   * If the template literal string contains expressions, then the expressions will be automatically
   * associated with placeholder names for you.
   *
   * For example:
   *
   * ```ts
   * $localize `Hi ${name}! There are ${items.length} items.`;
   * ```
   *
   * will generate a message-source of `Hi {$PH}! There are {$PH_1} items`.
   *
   * The recommended practice is to name the placeholder associated with each expression though.
   *
   * Do this by providing the placeholder name wrapped in `:` characters directly after the
   * expression. These placeholder names are stripped out of the rendered localized string.
   *
   * For example, to name the `items.length` expression placeholder `itemCount` you write:
   *
   * ```ts
   * $localize `There are ${items.length}:itemCount: items`;
   * ```
   *
   * **Escaping colon markers**
   *
   * If you need to use a `:` character directly at the start of a tagged string that has no
   * metadata block, or directly after a substitution expression that has no name you must escape
   * the `:` by preceding it with a backslash:
   *
   * For example:
   *
   * ```ts
   * // message has a metadata block so no need to escape colon
   * $localize `:some description::this message starts with a colon (:)`;
   * // no metadata block so the colon must be escaped
   * $localize `\:this message starts with a colon (:)`;
   * ```
   *
   * ```ts
   * // named substitution so no need to escape colon
   * $localize `${label}:label:: ${}`
   * // anonymous substitution so colon must be escaped
   * $localize `${label}\: ${}`
   * ```
   *
   * **Processing localized strings:**
   *
   * There are three scenarios:
   *
   * * **compile-time inlining**: the `$localize` tag is transformed at compile time by a
   * transpiler, removing the tag and replacing the template literal string with a translated
   * literal string from a collection of translations provided to the transpilation tool.
   *
   * * **run-time evaluation**: the `$localize` tag is a run-time function that replaces and
   * reorders the parts (static strings and expressions) of the template literal string with strings
   * from a collection of translations loaded at run-time.
   *
   * * **pass-through evaluation**: the `$localize` tag is a run-time function that simply evaluates
   * the original template literal string without applying any translations to the parts. This
   * version is used during development or where there is no need to translate the localized
   * template literals.
   *
   * @param messageParts a collection of the static parts of the template string.
   * @param expressions a collection of the values of each placeholder in the template string.
   * @returns the translated string, with the `messageParts` and `expressions` interleaved together.
   */
  const $localize: LocalizeFn;
}