83 lines
2.8 KiB
JavaScript
83 lines
2.8 KiB
JavaScript
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/*
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MIT License http://www.opensource.org/licenses/mit-license.php
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Author Tobias Koppers @sokra
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*/
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"use strict";
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/** @typedef {import("./Resolver").FileSystem} FileSystem */
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/** @typedef {{ paths: string[], segments: string[] }} GetPathsResult */
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/**
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* Walk `path` from tip to root, returning every ancestor directory (plus the
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* input itself) in `paths`, and each corresponding segment name in `segments`.
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*
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* The return value may be shared across callers via `getPathsCached` — treat
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* it as read-only. Callers that need to mutate (currently only
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* `SymlinkPlugin`) should `slice()` the arrays locally before writing.
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* @param {string} path path
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* @returns {GetPathsResult} paths and segments
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*/
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function getPaths(path) {
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if (path === "/") return { paths: ["/"], segments: [""] };
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const parts = path.split(/(.*?[\\/]+)/);
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const paths = [path];
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const segments = [parts[parts.length - 1]];
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let part = parts[parts.length - 1];
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path = path.slice(0, Math.max(0, path.length - part.length - 1));
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for (let i = parts.length - 2; i > 2; i -= 2) {
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paths.push(path);
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part = parts[i];
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path = path.slice(0, Math.max(0, path.length - part.length)) || "/";
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segments.push(part.slice(0, -1));
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}
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[, part] = parts;
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segments.push(part);
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paths.push(part);
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return {
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paths,
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segments,
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};
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}
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/**
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* Per-filesystem memoization of `getPaths`. Kept in a standalone WeakMap
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* rather than being hung off `resolver.pathCache` so that adding this cache
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* does not change the hidden-class shape of `pathCache` — which is accessed
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* on the hot path of every resolve as `resolver.pathCache.{join,dirname,
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* basename}.fn(...)`. CodSpeed caught that shape change as a ~1–2%
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* instruction-count regression on `cache-predicate`, so we keep pathCache
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* shape-stable by owning this cache here instead.
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*
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* The cache lifetime is tied to the filesystem object (same invariant as
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* `_pathCacheByFs` in `Resolver.js`): when the user swaps filesystems the
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* entries become unreachable and get collected.
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* @type {WeakMap<FileSystem, Map<string, GetPathsResult>>}
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*/
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const _getPathsCacheByFs = new WeakMap();
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/**
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* Memoized `getPaths`. The returned object is shared across callers — do
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* not mutate the `paths` or `segments` arrays in-place; `slice()` first if
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* you need a mutable copy.
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* @param {FileSystem} fileSystem filesystem used as the cache namespace
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* @param {string} path path
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* @returns {GetPathsResult} paths and segments
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*/
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function getPathsCached(fileSystem, path) {
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let cache = _getPathsCacheByFs.get(fileSystem);
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if (cache === undefined) {
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cache = new Map();
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_getPathsCacheByFs.set(fileSystem, cache);
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} else {
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const cached = cache.get(path);
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if (cached !== undefined) return cached;
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}
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const result = getPaths(path);
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cache.set(path, result);
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return result;
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}
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module.exports = getPaths;
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module.exports.getPathsCached = getPathsCached;
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