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rebasing-importer.ts
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rebasing-importer.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 { RawSourceMap } from '@ampproject/remapping';
import MagicString from 'magic-string';
import { readFileSync, readdirSync, statSync } from 'node:fs';
import { basename, dirname, extname, join, relative } from 'node:path';
import { fileURLToPath, pathToFileURL } from 'node:url';
import type { CanonicalizeContext, Importer, ImporterResult, Syntax } from 'sass';
import { findUrls } from './lexer';
/**
* A preprocessed cache entry for the files and directories within a previously searched
* directory when performing Sass import resolution.
*/
export interface DirectoryEntry {
files: Set<string>;
directories: Set<string>;
}
/**
* Ensures that a bare specifier URL path that is intended to be treated as
* a relative path has a leading `./` or `../` prefix.
*
* @param url A bare specifier URL path that should be considered relative.
* @returns
*/
function ensureRelative(url: string): string {
// Empty
if (!url) {
return url;
}
// Already relative
if (url[0] === '.' && (url[1] === '/' || (url[1] === '.' && url[2] === '/'))) {
return url;
}
// Needs prefix
return './' + url;
}
/**
* A Sass Importer base class that provides the load logic to rebase all `url()` functions
* within a stylesheet. The rebasing will ensure that the URLs in the output of the Sass compiler
* reflect the final filesystem location of the output CSS file.
*
* This class provides the core of the rebasing functionality. To ensure that each file is processed
* by this importer's load implementation, the Sass compiler requires the importer's canonicalize
* function to return a non-null value with the resolved location of the requested stylesheet.
* Concrete implementations of this class must provide this canonicalize functionality for rebasing
* to be effective.
*/
abstract class UrlRebasingImporter implements Importer<'sync'> {
/**
* @param entryDirectory The directory of the entry stylesheet that was passed to the Sass compiler.
* @param rebaseSourceMaps When provided, rebased files will have an intermediate sourcemap added to the Map
* which can be used to generate a final sourcemap that contains original sources.
*/
constructor(
private entryDirectory: string,
private rebaseSourceMaps?: Map<string, RawSourceMap>,
) {}
abstract canonicalize(url: string, options: { fromImport: boolean }): URL | null;
load(canonicalUrl: URL): ImporterResult | null {
const stylesheetPath = fileURLToPath(canonicalUrl);
const stylesheetDirectory = dirname(stylesheetPath);
let contents = readFileSync(stylesheetPath, 'utf-8');
// Rebase any URLs that are found
let updatedContents;
for (const { start, end, value } of findUrls(contents)) {
// Skip if value is empty or Webpack-specific prefix
if (value.length === 0 || value[0] === '~' || value[0] === '^') {
continue;
}
// Skip if value is a Sass variable.
// Sass variable usage either starts with a `$` or contains a namespace and a `.$`
if (value[0] === '$' || /^\w+\.\$/.test(value)) {
continue;
}
// Skip if root-relative, absolute or protocol relative url
if (/^((?:\w+:)?\/\/|data:|chrome:|#|\/)/.test(value)) {
continue;
}
const rebasedPath = relative(this.entryDirectory, join(stylesheetDirectory, value));
// Normalize path separators and escape characters
// https://developer.mozilla.org/en-US/docs/Web/CSS/url#syntax
const rebasedUrl = ensureRelative(
rebasedPath.replace(/\\/g, '/').replace(/[()\s'"]/g, '\\$&'),
);
updatedContents ??= new MagicString(contents);
// Always quote the URL to avoid potential downstream parsing problems
updatedContents.update(start, end, `"${rebasedUrl}"`);
}
if (updatedContents) {
contents = updatedContents.toString();
if (this.rebaseSourceMaps) {
// Generate an intermediate source map for the rebasing changes
const map = updatedContents.generateMap({
hires: 'boundary',
includeContent: true,
source: canonicalUrl.href,
});
this.rebaseSourceMaps.set(canonicalUrl.href, map as RawSourceMap);
}
}
let syntax: Syntax | undefined;
switch (extname(stylesheetPath).toLowerCase()) {
case '.css':
syntax = 'css';
break;
case '.sass':
syntax = 'indented';
break;
default:
syntax = 'scss';
break;
}
return {
contents,
syntax,
sourceMapUrl: canonicalUrl,
};
}
}
/**
* Provides the Sass importer logic to resolve relative stylesheet imports via both import and use rules
* and also rebase any `url()` function usage within those stylesheets. The rebasing will ensure that
* the URLs in the output of the Sass compiler reflect the final filesystem location of the output CSS file.
*/
export class RelativeUrlRebasingImporter extends UrlRebasingImporter {
constructor(
entryDirectory: string,
private directoryCache = new Map<string, DirectoryEntry>(),
rebaseSourceMaps?: Map<string, RawSourceMap>,
) {
super(entryDirectory, rebaseSourceMaps);
}
canonicalize(url: string, options: { fromImport: boolean }): URL | null {
return this.resolveImport(url, options.fromImport, true);
}
/**
* Attempts to resolve a provided URL to a stylesheet file using the Sass compiler's resolution algorithm.
* Based on https://github.com/sass/dart-sass/blob/44d6bb6ac72fe6b93f5bfec371a1fffb18e6b76d/lib/src/importer/utils.dart
* @param url The file protocol URL to resolve.
* @param fromImport If true, URL was from an import rule; otherwise from a use rule.
* @param checkDirectory If true, try checking for a directory with the base name containing an index file.
* @returns A full resolved URL of the stylesheet file or `null` if not found.
*/
private resolveImport(url: string, fromImport: boolean, checkDirectory: boolean): URL | null {
let stylesheetPath;
try {
stylesheetPath = fileURLToPath(url);
} catch {
// Only file protocol URLs are supported by this importer
return null;
}
const directory = dirname(stylesheetPath);
const extension = extname(stylesheetPath);
const hasStyleExtension =
extension === '.scss' || extension === '.sass' || extension === '.css';
// Remove the style extension if present to allow adding the `.import` suffix
const filename = basename(stylesheetPath, hasStyleExtension ? extension : undefined);
const importPotentials = new Set<string>();
const defaultPotentials = new Set<string>();
if (hasStyleExtension) {
if (fromImport) {
importPotentials.add(filename + '.import' + extension);
importPotentials.add('_' + filename + '.import' + extension);
}
defaultPotentials.add(filename + extension);
defaultPotentials.add('_' + filename + extension);
} else {
if (fromImport) {
importPotentials.add(filename + '.import.scss');
importPotentials.add(filename + '.import.sass');
importPotentials.add(filename + '.import.css');
importPotentials.add('_' + filename + '.import.scss');
importPotentials.add('_' + filename + '.import.sass');
importPotentials.add('_' + filename + '.import.css');
}
defaultPotentials.add(filename + '.scss');
defaultPotentials.add(filename + '.sass');
defaultPotentials.add(filename + '.css');
defaultPotentials.add('_' + filename + '.scss');
defaultPotentials.add('_' + filename + '.sass');
defaultPotentials.add('_' + filename + '.css');
}
let foundDefaults;
let foundImports;
let hasPotentialIndex = false;
let cachedEntries = this.directoryCache.get(directory);
if (cachedEntries) {
// If there is a preprocessed cache of the directory, perform an intersection of the potentials
// and the directory files.
const { files, directories } = cachedEntries;
foundDefaults = [...defaultPotentials].filter((potential) => files.has(potential));
foundImports = [...importPotentials].filter((potential) => files.has(potential));
hasPotentialIndex = checkDirectory && !hasStyleExtension && directories.has(filename);
} else {
// If no preprocessed cache exists, get the entries from the file system and, while searching,
// generate the cache for later requests.
let entries;
try {
entries = readdirSync(directory, { withFileTypes: true });
} catch {
return null;
}
foundDefaults = [];
foundImports = [];
cachedEntries = { files: new Set<string>(), directories: new Set<string>() };
for (const entry of entries) {
let isDirectory: boolean;
let isFile: boolean;
if (entry.isSymbolicLink()) {
const stats = statSync(join(entry.path, entry.name));
isDirectory = stats.isDirectory();
isFile = stats.isFile();
} else {
isDirectory = entry.isDirectory();
isFile = entry.isFile();
}
if (isDirectory) {
cachedEntries.directories.add(entry.name);
// Record if the name should be checked as a directory with an index file
if (checkDirectory && !hasStyleExtension && entry.name === filename) {
hasPotentialIndex = true;
}
}
if (!isFile) {
continue;
}
cachedEntries.files.add(entry.name);
if (importPotentials.has(entry.name)) {
foundImports.push(entry.name);
}
if (defaultPotentials.has(entry.name)) {
foundDefaults.push(entry.name);
}
}
this.directoryCache.set(directory, cachedEntries);
}
// `foundImports` will only contain elements if `options.fromImport` is true
const result = this.checkFound(foundImports) ?? this.checkFound(foundDefaults);
if (result !== null) {
return pathToFileURL(join(directory, result));
}
if (hasPotentialIndex) {
// Check for index files using filename as a directory
return this.resolveImport(url + '/index', fromImport, false);
}
return null;
}
/**
* Checks an array of potential stylesheet files to determine if there is a valid
* stylesheet file. More than one discovered file may indicate an error.
* @param found An array of discovered stylesheet files.
* @returns A fully resolved path for a stylesheet file or `null` if not found.
* @throws If there are ambiguous files discovered.
*/
private checkFound(found: string[]): string | null {
if (found.length === 0) {
// Not found
return null;
}
// More than one found file may be an error
if (found.length > 1) {
// Presence of CSS files alongside a Sass file does not cause an error
const foundWithoutCss = found.filter((element) => extname(element) !== '.css');
// If the length is zero then there are two or more css files
// If the length is more than one than there are two or more sass/scss files
if (foundWithoutCss.length !== 1) {
throw new Error('Ambiguous import detected.');
}
// Return the non-CSS file (sass/scss files have priority)
// https://github.com/sass/dart-sass/blob/44d6bb6ac72fe6b93f5bfec371a1fffb18e6b76d/lib/src/importer/utils.dart#L44-L47
return foundWithoutCss[0];
}
return found[0];
}
}
/**
* Provides the Sass importer logic to resolve module (npm package) stylesheet imports via both import and
* use rules and also rebase any `url()` function usage within those stylesheets. The rebasing will ensure that
* the URLs in the output of the Sass compiler reflect the final filesystem location of the output CSS file.
*/
export class ModuleUrlRebasingImporter extends RelativeUrlRebasingImporter {
constructor(
entryDirectory: string,
directoryCache: Map<string, DirectoryEntry>,
rebaseSourceMaps: Map<string, RawSourceMap> | undefined,
private finder: (specifier: string, options: CanonicalizeContext) => URL | null,
) {
super(entryDirectory, directoryCache, rebaseSourceMaps);
}
override canonicalize(url: string, options: CanonicalizeContext): URL | null {
if (url.startsWith('file://')) {
return super.canonicalize(url, options);
}
let result = this.finder(url, options);
result &&= super.canonicalize(result.href, options);
return result;
}
}
/**
* Provides the Sass importer logic to resolve load paths located stylesheet imports via both import and
* use rules and also rebase any `url()` function usage within those stylesheets. The rebasing will ensure that
* the URLs in the output of the Sass compiler reflect the final filesystem location of the output CSS file.
*/
export class LoadPathsUrlRebasingImporter extends RelativeUrlRebasingImporter {
constructor(
entryDirectory: string,
directoryCache: Map<string, DirectoryEntry>,
rebaseSourceMaps: Map<string, RawSourceMap> | undefined,
private loadPaths: Iterable<string>,
) {
super(entryDirectory, directoryCache, rebaseSourceMaps);
}
override canonicalize(url: string, options: { fromImport: boolean }): URL | null {
if (url.startsWith('file://')) {
return super.canonicalize(url, options);
}
let result = null;
for (const loadPath of this.loadPaths) {
result = super.canonicalize(pathToFileURL(join(loadPath, url)).href, options);
if (result !== null) {
break;
}
}
return result;
}
}
/**
* Workaround for Sass not calling instance methods with `this`.
* The `canonicalize` and `load` methods will be bound to the class instance.
* @param importer A Sass importer to bind.
* @returns The bound Sass importer.
*/
export function sassBindWorkaround<T extends Importer>(importer: T): T {
importer.canonicalize = importer.canonicalize.bind(importer);
importer.load = importer.load.bind(importer);
return importer;
}