perf: use lilconfig only when searching for config files outside git repo

Author: iiroj

.changeset/selfish-pillows-remember.md

@@ -0,0 +1,5 @@
+---
+'lint-staged': patch
+---
+
+To improve performance, only use `lilconfig` when searching for config files outside the git repo. In the regular case, _lint-staged_ finds the config files from the Git index and loads them directly.

lib/loadConfig.js

@@ -1,9 +1,9 @@
 /** @typedef {import('./index').Logger} Logger */
 
+import fs from 'node:fs/promises'
 import path from 'node:path'
 
 import debug from 'debug'
-import { lilconfig } from 'lilconfig'
 import YAML from 'yaml'
 
 import { dynamicImport } from './dynamicImport.js'
@@ -37,8 +37,10 @@ export const searchPlaces = [
 ]
 
 const jsonParse = (filePath, content) => {
+  const isPackageFile = PACKAGE_JSON_FILE.includes(path.basename(filePath))
   try {
-    return JSON.parse(content)
+    const json = JSON.parse(content)
+    return isPackageFile ? json[CONFIG_NAME] : json
   } catch (error) {
     if (path.basename(filePath) === PACKAGE_JSON_FILE) {
       debugLog('Ignoring invalid package file `%s` with content:\n%s', filePath, content)
@@ -64,6 +66,8 @@ const yamlParse = (filePath, content) => {
   }
 }
 
+const NO_EXT = 'noExt'
+
 /**
  * `lilconfig` doesn't support yaml files by default,
  * so we add custom loaders for those. Files without
@@ -77,10 +81,31 @@ const loaders = {
   '.cjs': dynamicImport,
   '.yaml': yamlParse,
   '.yml': yamlParse,
-  noExt: yamlParse,
+  [NO_EXT]: yamlParse,
+}
+
+const readFile = async (filepath) => {
+  const absolutePath = path.resolve(filepath)
+  const file = await fs.readFile(absolutePath)
+  return await file.toString()
 }
 
-const explorer = lilconfig(CONFIG_NAME, { searchPlaces, loaders })
+const loadConfigByExt = async (filepath) => {
+  filepath = path.resolve(filepath)
+  const ext = path.extname(filepath) || NO_EXT
+  const loader = loaders[ext]
+
+  /**
+   * No need to read file contents when loader only takes in the filepath argument
+   * and reads itself; this is for `lilconfig` compatibility
+   */
+  const content = loader.length > 1 ? await readFile(filepath) : undefined
+
+  return {
+    config: await loader(filepath, content),
+    filepath,
+  }
+}
 
 /**
  * @param {object} options
@@ -89,20 +114,22 @@ const explorer = lilconfig(CONFIG_NAME, { searchPlaces, loaders })
  */
 export const loadConfig = async ({ configPath, cwd }, logger) => {
   try {
+    let result
+
     if (configPath) {
       debugLog('Loading configuration from `%s`...', configPath)
+      result = await loadConfigByExt(resolveConfig(configPath))
     } else {
       debugLog('Searching for configuration from `%s`...', cwd)
+      const { lilconfig } = await import('lilconfig')
+      const explorer = lilconfig(CONFIG_NAME, { searchPlaces, loaders })
+      result = await explorer.search(cwd)
     }
 
-    const result = await (configPath
-      ? explorer.load(resolveConfig(configPath))
-      : explorer.search(cwd))
-
     if (!result) return {}
 
     // config is a promise when using the `dynamicImport` loader
-    const config = await result.config
+    const config = (await result.config) ?? null
     const filepath = result.filepath
 
     debugLog('Successfully loaded config from `%s`:\n%O', filepath, config)

test/unit/loadConfig.spec.js

@@ -286,7 +286,7 @@ describe('loadConfig', () => {
 
     const { config } = await loadConfig({ configPath: configFile }, logger)
 
-    expect(config).toBeUndefined()
+    expect(config).toBeNull()
 
     await fs.rm(configFile)
   })