Add improved webpack cache (#1916)

Related-to: GH-1468. Related-to: GH-1912. Reviewed-by: Remco Haszing <remcohaszing@gmail.com> Reviewed-by: Christian Murphy <christian.murphy.42@gmail.com>

Author: wooorm

packages/loader/lib/index.js

@@ -5,13 +5,20 @@
  * @typedef {Pick<CompileOptions, 'SourceMapGenerator'>} Defaults
  * @typedef {Omit<CompileOptions, 'SourceMapGenerator'>} Options
  * @typedef {import('webpack').LoaderContext<unknown>} LoaderContext
+ * @typedef {import('webpack').Compiler} WebpackCompiler
  * @typedef {(vfileCompatible: VFileCompatible) => Promise<VFile>} Process
  */
 
+import {createHash} from 'node:crypto'
 import {SourceMapGenerator} from 'source-map'
 import {createFormatAwareProcessors} from '@mdx-js/mdx/lib/util/create-format-aware-processors.js'
 
-/** @type {WeakMap<CompileOptions, Process>} */
+const own = {}.hasOwnProperty
+
+// Note: the cache is heavily inspired by:
+// <https://github.com/TypeStrong/ts-loader/blob/5c030bf/src/instance-cache.ts>
+const marker = /** @type {WebpackCompiler} */ ({})
+/** @type {WeakMap<WebpackCompiler, Map<string, Process>>} */
 const cache = new WeakMap()
 
 /**
@@ -28,6 +35,10 @@ export function loader(value, callback) {
  const defaults = this.sourceMap ? {SourceMapGenerator} : {}
  const options = /** @type {CompileOptions} */ (this.getOptions())
  const config = {...defaults, ...options}
+ const hash = getOptionsHash(options)
+ // Some loaders set `undefined` (see `TypeStrong/ts-loader`).
+ /* c8 ignore next */
+ const compiler = this._compiler || marker
 
  /* Removed option. */
  /* c8 ignore next 5 */
@@ -37,15 +48,44 @@ export function loader(value, callback) {
  )
  }
 
- let process = cache.get(config)
+ let map = cache.get(compiler)
+
+ if (!map) {
+ map = new Map()
+ cache.set(compiler, map)
+ }
+
+ let process = map.get(hash)
 
  if (!process) {
  process = createFormatAwareProcessors(config).process
- cache.set(config, process)
+ map.set(hash, process)
  }
 
  process({value, path: this.resourcePath}).then((file) => {
  callback(null, file.value, file.map)
  return file
  }, callback)
 }
+
+/**
+ * @param {Options} options
+ */
+function getOptionsHash(options) {
+ const hash = createHash('sha256')
+ /** @type {keyof Options} */
+ let key
+
+ for (key in options) {
+ if (own.call(options, key)) {
+ const value = options[key]
+
+ if (value !== undefined) {
+ const valueString = JSON.stringify(value)
+ hash.update(key + valueString)
+ }
+ }
+ }
+
+ return hash.digest('hex').slice(0, 16)
+}