feat: support async function tasks

README.md

@@ -153,12 +153,12 @@ Pass arguments to your commands separated by space as you would do in the shell.
 
 Starting from [v2.0.0](https://github.com/okonet/lint-staged/releases/tag/2.0.0) sequences of commands are supported. Pass an array of commands instead of a single one and they will run sequentially. This is useful for running autoformatting tools like `eslint --fix` or `stylefmt` but can be used for any arbitrary sequences.
 
-## Using JS functions to customize linter commands
+## Using JS functions to customize tasks
 
-When supplying configuration in JS format it is possible to define the linter command as a function which receives an array of staged filenames/paths and returns the complete linter command as a string. It is also possible to return an array of complete command strings, for example when the linter command supports only a single file input.
+When supplying configuration in JS format it is possible to define the task as a function, which will receive an array of staged filenames/paths and should return the complete command as a string. It is also possible to return an array of complete command strings, for example when the task supports only a single file input. The function can be either sync or async.
 
 ```ts
-type LinterFn = (filenames: string[]) => string | string[]
+type TaskFn = (filenames: string[]) => string | string[] | Promise<string | string[]>
 ```
 
 ### Example: Wrap filenames in single quotes and run once per file
@@ -196,7 +196,7 @@ const micromatch = require('micromatch')
 module.exports = {
   '*': allFiles => {
     const match = micromatch(allFiles, ['*.js', '*.ts'])
-    return `eslint ${match.join(" ")}`
+    return `eslint ${match.join(' ')}`
   }
 }
 ```
@@ -212,7 +212,7 @@ module.exports = {
   '*.js': files => {
     // from `files` filter those _NOT_ matching `*test.js`
     const match = micromatch.not(files, '*test.js')
-    return `eslint ${match.join(" ")}`
+    return `eslint ${match.join(' ')}`
   }
 }
 ```

lib/makeCmdTasks.js

@@ -13,41 +13,43 @@ const debug = require('debug')('lint-staged:make-cmd-tasks')
  * @param {string} options.gitDir
  * @param {Boolean} shell
  */
-module.exports = function makeCmdTasks({ commands, files, gitDir, shell }) {
+module.exports = async function makeCmdTasks({ commands, files, gitDir, shell }) {
   debug('Creating listr tasks for commands %o', commands)
   const commandsArray = Array.isArray(commands) ? commands : [commands]
+  const cmdTasks = []
 
-  return commandsArray.reduce((tasks, command) => {
+  for (const cmd of commandsArray) {
     // command function may return array of commands that already include `stagedFiles`
-    const isFn = typeof command === 'function'
-    const resolved = isFn ? command(files) : command
-    const commands = Array.isArray(resolved) ? resolved : [resolved] // Wrap non-array command as array
+    const isFn = typeof cmd === 'function'
+    const resolved = isFn ? await cmd(files) : cmd
+
+    const resolvedArray = Array.isArray(resolved) ? resolved : [resolved] // Wrap non-array command as array
 
     // Function command should not be used as the task title as-is
     // because the resolved string it might be very long
     // Create a matching command array with [file] in place of file names
-    let mockCommands
+    let mockCmdTasks
     if (isFn) {
       const mockFileList = Array(files.length).fill('[file]')
-      const resolved = command(mockFileList)
-      mockCommands = Array.isArray(resolved) ? resolved : [resolved]
+      const resolved = await cmd(mockFileList)
+      mockCmdTasks = Array.isArray(resolved) ? resolved : [resolved]
     }
 
-    commands.forEach((command, i) => {
+    for (const [i, command] of resolvedArray.entries()) {
       let title = isFn ? '[Function]' : command
-      if (isFn && mockCommands[i]) {
+      if (isFn && mockCmdTasks[i]) {
         // If command is a function, use the matching mock command as title,
         // but since might include multiple [file] arguments, shorten to one
-        title = mockCommands[i].replace(/\[file\].*\[file\]/, '[file]')
+        title = mockCmdTasks[i].replace(/\[file\].*\[file\]/, '[file]')
       }
 
-      tasks.push({
+      cmdTasks.push({
         title,
         command,
         task: resolveTaskFn({ command, files, gitDir, isFn, shell })
       })
-    })
+    }
+  }
 
-    return tasks
-  }, [])
+  return cmdTasks
 }

lib/runAll.js

@@ -81,8 +81,10 @@ module.exports = async function runAll(
 
   for (const [index, files] of stagedFileChunks.entries()) {
     const chunkTasks = generateTasks({ config, cwd, gitDir, files, relative })
-    const chunkListrTasks = chunkTasks.map(task => {
-      const subTasks = makeCmdTasks({
+    const chunkListrTasks = []
+
+    for (const task of chunkTasks) {
+      const subTasks = await makeCmdTasks({
         commands: task.commands,
         files: task.fileList,
         gitDir,
@@ -93,7 +95,7 @@ module.exports = async function runAll(
         hasDeprecatedGitAdd = true
       }
 
-      return {
+      chunkListrTasks.push({
         title: `Running tasks for ${task.pattern}`,
         task: async () =>
           new Listr(subTasks, {
@@ -109,8 +111,8 @@ module.exports = async function runAll(
           }
           return false
         }
-      }
-    })
+      })
+    }
 
     listrTasks.push({
       // No need to show number of task chunks when there's only one

test/makeCmdTasks.spec.js

@@ -58,13 +58,13 @@ describe('makeCmdTasks', () => {
     })
   })
 
-  it('should work with function linter returning a string', async () => {
+  it('should work with function task returning a string', async () => {
     const res = await makeCmdTasks({ commands: () => 'test', gitDir, files: ['test.js'] })
     expect(res.length).toBe(1)
     expect(res[0].title).toEqual('test')
   })
 
-  it('should work with function linter returning array of string', async () => {
+  it('should work with function task returning array of string', async () => {
     const res = await makeCmdTasks({
       commands: () => ['test', 'test2'],
       gitDir,
@@ -75,7 +75,7 @@ describe('makeCmdTasks', () => {
     expect(res[1].title).toEqual('test2')
   })
 
-  it('should work with function linter accepting arguments', async () => {
+  it('should work with function task accepting arguments', async () => {
     const res = await makeCmdTasks({
       commands: filenames => filenames.map(file => `test ${file}`),
       gitDir,
@@ -86,7 +86,7 @@ describe('makeCmdTasks', () => {
     expect(res[1].title).toEqual('test [file]')
   })
 
-  it('should work with array of mixed string and function linters', async () => {
+  it('should work with array of mixed string and function tasks', async () => {
     const res = await makeCmdTasks({
       commands: [() => 'test', 'test2', files => files.map(file => `test ${file}`)],
       gitDir,
@@ -109,4 +109,10 @@ describe('makeCmdTasks', () => {
     expect(res.length).toBe(1)
     expect(res[0].title).toEqual('test --file [file]')
   })
+
+  it('should work with async function tasks', async () => {
+    const res = await makeCmdTasks({ commands: async () => 'test', gitDir, files: ['test.js'] })
+    expect(res.length).toBe(1)
+    expect(res[0].title).toEqual('test')
+  })
 })