feat: add --check CLI option

README.md

@@ -101,6 +101,10 @@ Outputs the name of each file right before it is proccessed. This can be useful
 
 Prevent `git commit` if any files are fixed.
 
+### `--check`
+
+Check that files are correctly formatted, but don't format them. This is useful on CI to verify that all changed files in the current branch were correctly formatted.
+
 <!-- Undocumented = Unsupported :D
 
 ### `--config`

bin/pretty-quick.js

@@ -36,7 +36,13 @@ const prettyQuickResult = prettyQuick(
       console.log(`✍️  Fixing up ${chalk.bold(file)}.`);
     },
 
-    onExamineFile: file => {
+    onCheckFile: (file, isFormatted) => {
+      if (!isFormatted) {
+        console.log(`⛔️  Check failed: ${chalk.bold(file)}`);
+      }
+    },
+
+    onProcessFile: file => {
       console.log(`🔍  Examining ${chalk.bold(file)}.`);
     },
   })
@@ -56,5 +62,10 @@ if (prettyQuickResult.success) {
       '✗ File had to be prettified and prettyQuick was set to bail mode.'
     );
   }
+  if (prettyQuickResult.errors.indexOf('CHECK_FAILED') !== -1) {
+    console.log(
+      '✗ Code style issues found in the above file(s). Forgot to run Prettier?'
+    );
+  }
   process.exit(1); // ensure git hooks abort
 }

src/__tests__/scm-git.test.js

@@ -295,24 +295,24 @@ describe('with git', () => {
     });
   });
 
-  test('with --verbose calls onExamineFile', () => {
-    const onExamineFile = jest.fn();
+  test('with --verbose calls onProcessFile', () => {
+    const onProcessFile = jest.fn();
     mockGitFs();
 
-    prettyQuick('root', { since: 'banana', verbose: true, onExamineFile });
+    prettyQuick('root', { since: 'banana', verbose: true, onProcessFile });
 
-    expect(onExamineFile).toHaveBeenCalledWith('./foo.js');
-    expect(onExamineFile).toHaveBeenCalledWith('./bar.md');
+    expect(onProcessFile).toHaveBeenCalledWith('./foo.js');
+    expect(onProcessFile).toHaveBeenCalledWith('./bar.md');
   });
 
-  test('without --verbose does NOT call onExamineFile', () => {
-    const onExamineFile = jest.fn();
+  test('without --verbose does NOT call onProcessFile', () => {
+    const onProcessFile = jest.fn();
     mockGitFs();
 
-    prettyQuick('root', { since: 'banana', onExamineFile });
+    prettyQuick('root', { since: 'banana', onProcessFile });
 
-    expect(onExamineFile).not.toHaveBeenCalledWith('./foo.js');
-    expect(onExamineFile).not.toHaveBeenCalledWith('./bar.md');
+    expect(onProcessFile).not.toHaveBeenCalledWith('./foo.js');
+    expect(onProcessFile).not.toHaveBeenCalledWith('./bar.md');
   });
 
   test('ignore files matching patterns from the repositories root .prettierignore', () => {

src/__tests__/scm-hg.test.js

@@ -196,22 +196,22 @@ describe('with hg', () => {
     });
   });
 
-  test('with --verbose calls onExamineFile', () => {
-    const onExamineFile = jest.fn();
+  test('with --verbose calls onProcessFile', () => {
+    const onProcessFile = jest.fn();
     mockHgFs();
-    prettyQuick('root', { since: 'banana', verbose: true, onExamineFile });
+    prettyQuick('root', { since: 'banana', verbose: true, onProcessFile });
 
-    expect(onExamineFile).toHaveBeenCalledWith('./foo.js');
-    expect(onExamineFile).toHaveBeenCalledWith('./bar.md');
+    expect(onProcessFile).toHaveBeenCalledWith('./foo.js');
+    expect(onProcessFile).toHaveBeenCalledWith('./bar.md');
   });
 
-  test('without --verbose does NOT call onExamineFile', () => {
-    const onExamineFile = jest.fn();
+  test('without --verbose does NOT call onProcessFile', () => {
+    const onProcessFile = jest.fn();
     mockHgFs();
-    prettyQuick('root', { since: 'banana', onExamineFile });
+    prettyQuick('root', { since: 'banana', onProcessFile });
 
-    expect(onExamineFile).not.toHaveBeenCalledWith('./foo.js');
-    expect(onExamineFile).not.toHaveBeenCalledWith('./bar.md');
+    expect(onProcessFile).not.toHaveBeenCalledWith('./foo.js');
+    expect(onProcessFile).not.toHaveBeenCalledWith('./bar.md');
   });
 
   test('ignore files matching patterns from the repositories root .prettierignore', () => {

src/index.js

@@ -1,5 +1,5 @@
 import scms from './scms';
-import formatFiles from './formatFiles';
+import processFiles from './processFiles';
 import createIgnorer from './createIgnorer';
 import createMatcher from './createMatcher';
 import isSupportedExtension from './isSupportedExtension';
@@ -14,12 +14,14 @@ export default (
     restage = true,
     branch,
     bail,
+    check,
     verbose,
     onFoundSinceRevision,
     onFoundChangedFiles,
     onPartiallyStagedFile,
+    onProcessFile,
+    onCheckFile,
     onWriteFile,
-    onExamineFile,
   } = {}
 ) => {
   const scm = scms(currentDirectory);
@@ -60,7 +62,8 @@ export default (
 
   const failReasons = new Set();
 
-  formatFiles(directory, changedFiles, {
+  processFiles(directory, changedFiles, {
+    check,
     config,
     onWriteFile: file => {
       onWriteFile && onWriteFile(file);
@@ -76,7 +79,13 @@ export default (
         }
       }
     },
-    onExamineFile: verbose && onExamineFile,
+    onCheckFile: (file, isFormatted) => {
+      onCheckFile && onCheckFile(file, isFormatted);
+      if (!isFormatted) {
+        failReasons.add('CHECK_FAILED');
+      }
+    },
+    onProcessFile: verbose && onProcessFile,
   });
 
   return {

src/processFiles.js

@@ -0,0 +1,36 @@
+import { readFileSync, writeFileSync } from 'fs';
+import * as prettier from 'prettier';
+import { join } from 'path';
+
+export default (
+  directory,
+  files,
+  { check, config, onProcessFile, onCheckFile, onWriteFile } = {}
+) => {
+  for (const relative of files) {
+    onProcessFile && onProcessFile(relative);
+    const file = join(directory, relative);
+    const options = Object.assign(
+      {},
+      prettier.resolveConfig.sync(file, {
+        config,
+        editorconfig: true,
+      }),
+      { filepath: file }
+    );
+    const input = readFileSync(file, 'utf8');
+
+    if (check) {
+      const isFormatted = prettier.check(input, options);
+      onCheckFile && onCheckFile(relative, isFormatted);
+      continue;
+    }
+
+    const output = prettier.format(input, options);
+
+    if (output !== input) {
+      writeFileSync(file, output);
+      onWriteFile && onWriteFile(relative);
+    }
+  }
+};