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image_loader.ts
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image_loader.ts
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/**
* @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 {InjectionToken, Provider, ɵRuntimeError as RuntimeError} from '@angular/core';
import {RuntimeErrorCode} from '../../../errors';
import {PRECONNECT_CHECK_BLOCKLIST} from '../preconnect_link_checker';
import {isAbsoluteUrl, isValidPath, normalizePath, normalizeSrc} from '../url';
/**
* Config options recognized by the image loader function.
*
* @see `ImageLoader`
* @see `NgOptimizedImage`
* @publicApi
* @developerPreview
*/
export interface ImageLoaderConfig {
/**
* Image file name to be added to the image request URL.
*/
src: string;
/**
* Width of the requested image (to be used when generating srcset).
*/
width?: number;
}
/**
* Represents an image loader function. Image loader functions are used by the
* NgOptimizedImage directive to produce full image URL based on the image name and its width.
*
* @publicApi
* @developerPreview
*/
export type ImageLoader = (config: ImageLoaderConfig) => string;
/**
* Noop image loader that does no transformation to the original src and just returns it as is.
* This loader is used as a default one if more specific logic is not provided in an app config.
*
* @see `ImageLoader`
* @see `NgOptimizedImage`
*/
const noopImageLoader = (config: ImageLoaderConfig) => config.src;
/**
* Injection token that configures the image loader function.
*
* @see `ImageLoader`
* @see `NgOptimizedImage`
* @publicApi
* @developerPreview
*/
export const IMAGE_LOADER = new InjectionToken<ImageLoader>('ImageLoader', {
providedIn: 'root',
factory: () => noopImageLoader,
});
/**
* Internal helper function that makes it easier to introduce custom image loaders for the
* `NgOptimizedImage` directive. It is enough to specify a URL builder function to obtain full DI
* configuration for a given loader: a DI token corresponding to the actual loader function, plus DI
* tokens managing preconnect check functionality.
* @param buildUrlFn a function returning a full URL based on loader's configuration
* @param exampleUrls example of full URLs for a given loader (used in error messages)
* @returns a set of DI providers corresponding to the configured image loader
*/
export function createImageLoader(
buildUrlFn: (path: string, config: ImageLoaderConfig) => string, exampleUrls?: string[]) {
return function provideImageLoader(
path: string, options: {ensurePreconnect?: boolean} = {ensurePreconnect: true}) {
if (!isValidPath(path)) {
throwInvalidPathError(path, exampleUrls || []);
}
// The trailing / is stripped (if provided) to make URL construction (concatenation) easier in
// the individual loader functions.
path = normalizePath(path);
const loaderFn = (config: ImageLoaderConfig) => {
if (isAbsoluteUrl(config.src)) {
// Image loader functions expect an image file name (e.g. `my-image.png`)
// or a relative path + a file name (e.g. `/a/b/c/my-image.png`) as an input,
// so the final absolute URL can be constructed.
// When an absolute URL is provided instead - the loader can not
// build a final URL, thus the error is thrown to indicate that.
throwUnexpectedAbsoluteUrlError(path, config.src);
}
return buildUrlFn(path, {...config, src: normalizeSrc(config.src)});
};
const providers: Provider[] = [{provide: IMAGE_LOADER, useValue: loaderFn}];
if (ngDevMode && options.ensurePreconnect === false) {
providers.push({provide: PRECONNECT_CHECK_BLOCKLIST, useValue: [path], multi: true});
}
return providers;
};
}
function throwInvalidPathError(path: unknown, exampleUrls: string[]): never {
throw new RuntimeError(
RuntimeErrorCode.INVALID_LOADER_ARGUMENTS,
ngDevMode &&
`Image loader has detected an invalid path (\`${path}\`). ` +
`To fix this, supply a path using one of the following formats: ${
exampleUrls.join(' or ')}`);
}
function throwUnexpectedAbsoluteUrlError(path: string, url: string): never {
throw new RuntimeError(
RuntimeErrorCode.INVALID_LOADER_ARGUMENTS,
ngDevMode &&
`Image loader has detected a \`<img>\` tag with an invalid \`rawSrc\` attribute: ${
url}. ` +
`This image loader expects \`rawSrc\` to be a relative URL - ` +
`however the provided value is an absolute URL. ` +
`To fix this, provide \`rawSrc\` as a path relative to the base URL ` +
`configured for this loader (\`${path}\`).`);
}