fix: correctly handle incorrect patterns withs braces of only single …

…value

Technically brace patterns like `*.{js}` are invalid because braces should
always contain at least one comma or a sequence,
for example `*.{js,ts}` or `file{1..10}.js`.

The `micromatch` library used to match patterns to files will silently ignore
such invalid braces and thus lead to the pattern always matching zero files.
This is a unintuitive, so lint-staged should normalize such cases
by simply removing the unnecessary braces before matching files.

lib/generateTasks.js

@@ -6,6 +6,19 @@ const path = require('path')
 
 const debug = require('debug')('lint-staged:gen-tasks')
 
+const { incorrectBraces } = require('./messages')
+
+// Braces with a single value like `*.{js}` are invalid
+// and thus ignored by micromatch. This regex matches all occurrences of
+// two curly braces without a `,` or `..` between them, to make sure
+// users can still accidentally use them without
+// some linters never matching anything.
+//
+// For example `.{js,ts}` or `file_{1..10}` are valid but `*.{js}` is not.
+//
+// See: https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html
+const BRACES_REGEXP = /({)(?:(?!,|\.\.).)*?(})/g
+
 /**
  * Generates all task commands, and filelist
  *
@@ -16,33 +29,51 @@ const debug = require('debug')('lint-staged:gen-tasks')
  * @param {boolean} [options.files] - Staged filepaths
  * @param {boolean} [options.relative] - Whether filepaths to should be relative to gitDir
  */
-const generateTasks = ({ config, cwd = process.cwd(), gitDir, files, relative = false }) => {
+const generateTasks = (
+  { config, cwd = process.cwd(), gitDir, files, relative = false },
+  logger
+) => {
   debug('Generating linter tasks')
 
   const absoluteFiles = files.map((file) => normalize(path.resolve(gitDir, file)))
   const relativeFiles = absoluteFiles.map((file) => normalize(path.relative(cwd, file)))
 
-  return Object.entries(config).map(([pattern, commands]) => {
+  return Object.entries(config).map(([rawPattern, commands]) => {
+    let pattern = rawPattern
+
     const isParentDirPattern = pattern.startsWith('../')
 
-    const fileList = micromatch(
-      relativeFiles
-        // Only worry about children of the CWD unless the pattern explicitly
-        // specifies that it concerns a parent directory.
-        .filter((file) => {
-          if (isParentDirPattern) return true
-          return !file.startsWith('..') && !path.isAbsolute(file)
-        }),
-      pattern,
-      {
-        cwd,
-        dot: true,
-        // If pattern doesn't look like a path, enable `matchBase` to
-        // match against filenames in every directory. This makes `*.js`
-        // match both `test.js` and `subdirectory/test.js`.
-        matchBase: !pattern.includes('/'),
-      }
-    ).map((file) => normalize(relative ? file : path.resolve(cwd, file)))
+    // Only worry about children of the CWD unless the pattern explicitly
+    // specifies that it concerns a parent directory.
+    const filteredFiles = relativeFiles.filter((file) => {
+      if (isParentDirPattern) return true
+      return !file.startsWith('..') && !path.isAbsolute(file)
+    })
+
+    // Remove "extra" brackets when they contain only a single value
+    let hadIncorrectBraces = false
+    while (BRACES_REGEXP.exec(rawPattern)) {
+      hadIncorrectBraces = true
+      pattern = pattern.replace(/{/, '')
+      pattern = pattern.replace(/}/, '')
+    }
+
+    // Warn the user about incorrect brackets usage
+    if (hadIncorrectBraces) {
+      logger.warn(incorrectBraces(rawPattern, pattern))
+    }
+
+    const matches = micromatch(filteredFiles, pattern, {
+      cwd,
+      dot: true,
+      // If the pattern doesn't look like a path, enable `matchBase` to
+      // match against filenames in every directory. This makes `*.js`
+      // match both `test.js` and `subdirectory/test.js`.
+      matchBase: !pattern.includes('/'),
+      strictBrackets: true,
+    })
+
+    const fileList = matches.map((file) => normalize(relative ? file : path.resolve(cwd, file)))
 
     const task = { pattern, commands, fileList }
     debug('Generated task: \n%O', task)

lib/messages.js

@@ -21,6 +21,11 @@ const DEPRECATED_GIT_ADD = `${warning} ${chalk.yellow(
 )}
 `
 
+const incorrectBraces = (before, after) => `${warning} ${chalk.yellow(
+  `Detected incorrect braces with only single value: \`${before}\`. Reformatted as: \`${after}\``
+)}
+`
+
 const TASK_ERROR = 'Skipped because of errors from tasks.'
 
 const SKIPPED_GIT_ERROR = 'Skipped because of previous git error.'
@@ -44,6 +49,7 @@ const CONFIG_STDIN_ERROR = 'Error: Could not read config from stdin.'
 module.exports = {
   NOT_GIT_REPO,
   FAILED_GET_STAGED_FILES,
+  incorrectBraces,
   NO_STAGED_FILES,
   NO_TASKS,
   skippingBackup,

lib/runAll.js

@@ -129,7 +129,7 @@ const runAll = async (
   const matchedFiles = new Set()
 
   for (const [index, files] of stagedFileChunks.entries()) {
-    const chunkTasks = generateTasks({ config, cwd, gitDir, files, relative })
+    const chunkTasks = generateTasks({ config, cwd, gitDir, files, relative }, logger)
     const chunkListrTasks = []
 
     for (const task of chunkTasks) {

test/generateTasks.spec.js

@@ -1,5 +1,6 @@
-import os from 'os'
+import makeConsoleMock from 'consolemock'
 import normalize from 'normalize-path'
+import os from 'os'
 import path from 'path'
 
 import generateTasks from '../lib/generateTasks'
@@ -153,6 +154,74 @@ describe('generateTasks', () => {
     })
   })
 
+  it('should match pattern "*.{js}" and show warning', async () => {
+    const logger = makeConsoleMock()
+    const result = await generateTasks(
+      {
+        config: {
+          '*.{js}': 'lint',
+        },
+        cwd,
+        gitDir,
+        files,
+      },
+      logger
+    )
+    const linter = result.find((item) => item.pattern === '*.js')
+
+    expect(linter).toEqual({
+      pattern: '*.js',
+      commands: 'lint',
+      fileList: [
+        `${gitDir}/test.js`,
+        `${gitDir}/deeper/test.js`,
+        `${gitDir}/deeper/test2.js`,
+        `${gitDir}/even/deeper/test.js`,
+        `${gitDir}/.hidden/test.js`,
+      ].map(normalizePath),
+    })
+
+    expect(logger.printHistory()).toMatchInlineSnapshot(`
+      "
+      WARN ‼ Detected incorrect braces with only single value: \`*.{js}\`. Reformatted as: \`*.js\`
+      "
+    `)
+  })
+
+  it('should match pattern "*.{c}{s}{s}" and show warning', async () => {
+    const logger = makeConsoleMock()
+    const result = await generateTasks(
+      {
+        config: {
+          '*.{c}{s}{s}': 'lint',
+        },
+        cwd,
+        gitDir,
+        files,
+      },
+      logger
+    )
+    const linter = result.find((item) => item.pattern === '*.css')
+
+    expect(linter).toEqual({
+      pattern: '*.css',
+      commands: 'lint',
+      fileList: [
+        `${gitDir}/test.css`,
+        `${gitDir}/deeper/test.css`,
+        `${gitDir}/deeper/test2.css`,
+        `${gitDir}/even/deeper/test.css`,
+        `${gitDir}/.hidden/test.css`,
+      ].map(normalizePath),
+    })
+
+    expect(logger.printHistory()).toMatchInlineSnapshot(`
+      "
+      WARN ‼ Detected incorrect braces with only single value: \`*.{c}{s}{s}\`. Reformatted as: \`*.css\`
+      "
+    `)
+  })
+
   it('should not match files in parent directory by default', async () => {
     const result = await generateTasks({
       config,