feat: performance improvement via cache

packages/eslint-plugin-mdx/src/rules/helpers.ts

@@ -1,11 +1,12 @@
+import fs from 'fs'
 import path from 'path'
 
 import { cosmiconfigSync } from 'cosmiconfig'
-import type { CosmiconfigResult } from 'cosmiconfig/dist/types'
 import { arrayify } from 'eslint-mdx'
 import remarkMdx from 'remark-mdx'
 import remarkParse from 'remark-parse'
 import remarkStringify from 'remark-stringify'
+import type { FrozenProcessor } from 'unified'
 import unified from 'unified'
 
 import type { RemarkConfig, RemarkPlugin } from './types'
@@ -39,74 +40,109 @@ export const requirePkg = <T>(
   throw error
 }
 
-let searchSync: (searchFrom?: string) => CosmiconfigResult
+/**
+ * Given a filepath, get the nearest path that is a regular file.
+ * The filepath provided by eslint may be a virtual filepath rather than a file
+ * on disk. This attempts to transform a virtual path into an on-disk path
+ */
+export const getPhysicalFilename = (filename: string): string => {
+  try {
+    if (fs.statSync(filename).isFile()) {
+      return filename
+    }
+  } catch (err) {
+    // https://github.com/eslint/eslint/issues/11989
+    if ((err as { code: string }).code === 'ENOTDIR') {
+      return getPhysicalFilename(path.dirname(filename))
+    }
+  }
+
+  return filename
+}
 
 export const remarkProcessor = unified().use(remarkParse).freeze()
 
+const explorer = cosmiconfigSync('remark', {
+  packageProp: 'remarkConfig',
+})
+
+// @internal - exported for testing
+export const processorCache = new Map<string, FrozenProcessor>()
+
+// eslint-disable-next-line sonarjs/cognitive-complexity
 export const getRemarkProcessor = (searchFrom: string, isMdx: boolean) => {
-  if (!searchSync) {
-    searchSync = cosmiconfigSync('remark', {
-      packageProp: 'remarkConfig',
-    }).search
+  const initCacheKey = `${String(isMdx)}-${searchFrom}`
+
+  let cachedProcessor = processorCache.get(initCacheKey)
+
+  if (cachedProcessor) {
+    return cachedProcessor
   }
 
-  let result: Partial<CosmiconfigResult>
+  const result = explorer.search(searchFrom)
 
-  try {
-    result = searchSync(searchFrom)
-  } catch (err) {
-    // https://github.com/eslint/eslint/issues/11989
-    /* istanbul ignore if */
-    if (
-      (err as { code?: string }).code !== 'ENOTDIR' ||
-      !/[/\\]\d+_[^/\\]*\.[\da-z]+$/i.test(searchFrom)
-    ) {
-      throw err
-    }
-    try {
-      result = searchSync(path.dirname(searchFrom))
-    } catch {
-      /* istanbul ignore next */
-      throw err
-    }
+  const cacheKey = result ? `${String(isMdx)}-${result.filepath}` : ''
+
+  cachedProcessor = processorCache.get(cacheKey)
+
+  if (cachedProcessor) {
+    return cachedProcessor
   }
 
-  /* istanbul ignore next */
-  const { plugins = [], settings } = (result?.config ||
-    {}) as Partial<RemarkConfig>
+  if (result) {
+    /* istanbul ignore next */
+    const { plugins = [], settings } = (result.config ||
+      {}) as Partial<RemarkConfig>
 
-  // disable this rule automatically since we already have a parser option `extensions`
-  // only disable this plugin if there are at least one plugin enabled
-  // otherwise `result` could be null inside `plugins.reduce`
-  /* istanbul ignore else */
-  if (plugins.length > 0) {
-    try {
-      // eslint-disable-next-line node/no-extraneous-require
-      plugins.push([require.resolve('remark-lint-file-extension'), false])
-    } catch {
-      // just ignore if the package does not exist
+    // disable this rule automatically since we already have a parser option `extensions`
+    // only disable this plugin if there are at least one plugin enabled
+    // otherwise it is redundant
+    /* istanbul ignore else */
+    if (plugins.length > 0) {
+      try {
+        // eslint-disable-next-line node/no-extraneous-require
+        plugins.push([require.resolve('remark-lint-file-extension'), false])
+      } catch {
+        // just ignore if the package does not exist
+      }
+    }
+
+    const initProcessor = remarkProcessor()
+      .use({ settings })
+      .use(remarkStringify)
+
+    if (isMdx) {
+      initProcessor.use(remarkMdx)
     }
-  }
 
-  const initProcessor = remarkProcessor().use({ settings }).use(remarkStringify)
+    cachedProcessor = plugins
+      .reduce((processor, pluginWithSettings) => {
+        const [plugin, ...pluginSettings] = arrayify(pluginWithSettings) as [
+          RemarkPlugin,
+          ...unknown[]
+        ]
+        return processor.use(
+          /* istanbul ignore next */
+          typeof plugin === 'string'
+            ? requirePkg(plugin, 'remark', result.filepath)
+            : plugin,
+          ...pluginSettings,
+        )
+      }, initProcessor)
+      .freeze()
+  } else {
+    const initProcessor = remarkProcessor().use(remarkStringify)
 
-  if (isMdx) {
-    initProcessor.use(remarkMdx)
+    if (isMdx) {
+      initProcessor.use(remarkMdx)
+    }
+
+    cachedProcessor = initProcessor.freeze()
   }
 
-  return plugins
-    .reduce((processor, pluginWithSettings) => {
-      const [plugin, ...pluginSettings] = arrayify(pluginWithSettings) as [
-        RemarkPlugin,
-        ...unknown[]
-      ]
-      return processor.use(
-        /* istanbul ignore next */
-        typeof plugin === 'string'
-          ? requirePkg(plugin, 'remark', result.filepath)
-          : plugin,
-        ...pluginSettings,
-      )
-    }, initProcessor)
-    .freeze()
+  processorCache
+    .set(initCacheKey, cachedProcessor)
+    .set(cacheKey, cachedProcessor)
+
+  return cachedProcessor
 }

packages/eslint-plugin-mdx/src/rules/remark.ts

@@ -5,7 +5,7 @@ import type { ParserOptions } from 'eslint-mdx'
 import { DEFAULT_EXTENSIONS, MARKDOWN_EXTENSIONS } from 'eslint-mdx'
 import vfile from 'vfile'
 
-import { getRemarkProcessor } from './helpers'
+import { getPhysicalFilename, getRemarkProcessor } from './helpers'
 import type { RemarkLintMessage } from './types'
 
 export const remark: Rule.RuleModule = {
@@ -37,7 +37,10 @@ export const remark: Rule.RuleModule = {
           return
         }
         const sourceText = sourceCode.getText(node)
-        const remarkProcessor = getRemarkProcessor(filename, isMdx)
+        const remarkProcessor = getRemarkProcessor(
+          getPhysicalFilename(filename),
+          isMdx,
+        )
         const file = vfile({
           path: filename,
           contents: sourceText,

test/remark.test.ts

@@ -0,0 +1,72 @@
+import path from 'path'
+
+import { DEFAULT_PARSER_OPTIONS as parserOptions } from 'eslint-mdx'
+// @ts-ignore - processorCache is an internal API
+import { processorCache, remark } from 'eslint-plugin-mdx'
+import { homedir } from 'os'
+
+import { parser, ruleTester } from './helpers'
+
+const userDir = homedir()
+
+ruleTester.run('remark 1', remark, {
+  valid: [
+    {
+      code: '<header>Header1</header>',
+      parser,
+      parserOptions,
+      filename: 'remark.mdx',
+    },
+    {
+      code: '<header>Header2</header>',
+      parser,
+      parserOptions,
+      filename: path.resolve(__filename, '0-fake.mdx'),
+    },
+    {
+      code: '<header>Header3</header>',
+      parser,
+      parserOptions,
+      filename: path.resolve(__dirname, 'fixtures/dir.mdx'),
+    },
+    {
+      code: '<header>Header4</header>',
+      parser,
+      parserOptions,
+      filename: path.resolve(userDir, '../test.mdx'),
+    },
+    {
+      code: '<header>Header5</header>',
+      parser,
+      parserOptions,
+      // dark hack
+      get filename() {
+        // eslint-disable-next-line @typescript-eslint/no-unsafe-call, @typescript-eslint/no-unsafe-member-access
+        processorCache.clear()
+        return path.resolve(userDir, '../test.md')
+      },
+    },
+  ],
+  invalid: [
+    {
+      code: '<header>Header</header>',
+      parser,
+      parserOptions,
+      filename: path.resolve(__filename, '0_fake_virtual_filename.mdx'),
+      errors: [
+        {
+          message: JSON.stringify({
+            reason: 'Do not use `_` in a file name',
+            source: 'remark-lint',
+            ruleId: 'no-file-name-irregular-characters',
+            severity: 1,
+          }),
+          line: null,
+          column: 0,
+          endLine: null,
+          endColumn: 0,
+        },
+      ],
+    },
+  ],
+})