Scripts: Add Prettier formatting script

.prettierrc.js

@@ -0,0 +1,3 @@
+// Import the default config file and expose it in the project root.
+// Useful for editor integrations.
+module.exports = require( '@wordpress/scripts/config/.prettierrc.js' );

package.json

@@ -172,6 +172,7 @@
 		"fixtures:server-registered": "wp-scripts env docker-run php ./bin/get-server-blocks.php > test/integration/full-content/server-registered.json",
 		"fixtures:generate": "npm run fixtures:server-registered && cross-env GENERATE_MISSING_FIXTURES=y npm run test-unit",
 		"fixtures:regenerate": "npm run fixtures:clean && npm run fixtures:generate",
+		"format-js": "wp-scripts format-js",
 		"lint": "concurrently \"npm run lint-js\" \"npm run lint-pkg-json\" \"npm run lint-css\" \"npm run lint-types\"",
 		"lint-js": "wp-scripts lint-js",
 		"lint-js:fix": "npm run lint-js -- --fix",

packages/scripts/config/.prettierrc.js

@@ -0,0 +1,12 @@
+module.exports = {
+	useTabs: true,
+	tabWidth: 2,
+	printWidth: 100,
+	singleQuote: true,
+	trailingComma: 'es5',
+	bracketSpacing: true,
+	parenSpacing: true,
+	jsxBracketSameLine: false,
+	semi: true,
+	arrowParens: 'always',
+};

packages/scripts/package.json

@@ -44,13 +44,15 @@
 		"command-exists": "^1.2.8",
 		"cross-spawn": "^5.1.0",
 		"decompress-zip": "^0.2.2",
+		"dir-glob": "^3.0.1",
 		"eslint": "^6.1.0",
 		"jest": "^24.7.1",
 		"jest-puppeteer": "^4.3.0",
 		"js-yaml": "^3.13.1",
 		"lodash": "^4.17.15",
 		"minimist": "^1.2.0",
 		"npm-package-json-lint": "^4.0.2",
+		"prettier": "npm:wp-prettier@^1.18.2",
 		"puppeteer": "^1.20.0",
 		"read-pkg-up": "^1.0.1",
 		"request": "^2.88.0",

packages/scripts/scripts/format-js.js

@@ -0,0 +1,76 @@
+/**
+ * External dependencies
+ */
+const { sync: spawn } = require( 'cross-spawn' );
+const { sync: resolveBin } = require( 'resolve-bin' );
+const { sync: dirGlob } = require( 'dir-glob' );
+
+/**
+ * Internal dependencies
+ */
+const {
+	fromConfigRoot,
+	fromProjectRoot,
+	getArgFromCLI,
+	getFileArgsFromCLI,
+	hasArgInCLI,
+	hasPackageProp,
+	hasProjectFile,
+} = require( '../utils' );
+
+// See: https://prettier.io/docs/en/configuration.html
+const hasProjectPrettierConfig =
+	hasProjectFile( '.prettierrc' ) ||
+	hasProjectFile( '.prettierrc.json' ) ||
+	hasProjectFile( '.prettierrc.yaml' ) ||
+	hasProjectFile( '.prettierrc.yml' ) ||
+	hasProjectFile( '.prettierrc.js' ) ||
+	hasProjectFile( '.prettierrc.config.js' ) ||
+	hasProjectFile( '.prettierrc.toml' ) ||
+	hasPackageProp( 'prettier' );
+
+// Get the configuration file, with preference highest to lowers:
+// 1. use the `--config` arg from CLI
+// 2. use configuration provided by the project
+// 3. use the default provided in the scripts module
+let configArgs;
+const configFromCLI = getArgFromCLI( '--config' );
+if ( configFromCLI ) {
+	configArgs = [ '--config', configFromCLI ];
+} else if ( hasProjectPrettierConfig ) {
+	configArgs = []; // no `--config` when project configuration is found: Prettier will find it
+} else {
+	configArgs = [ '--config', fromConfigRoot( '.prettierrc.js' ) ];
+}
+
+// If `--ignore-path` is not explicitly specified, use the project's or global .eslintignore
+let ignorePath = getArgFromCLI( '--ignore-path' );
+if ( ! ignorePath ) {
+	if ( hasProjectFile( '.eslintignore' ) ) {
+		ignorePath = fromProjectRoot( '.eslintignore' );
+	} else {
+		ignorePath = fromConfigRoot( '.eslintignore' );
+	}
+}
+const ignoreArgs = [ '--ignore-path', ignorePath ];
+
+// forward the --require-pragma option that formats only files that already have the @format
+// pragma in the first docblock.
+const pragmaArgs = hasArgInCLI( '--require-pragma' ) ? [ '--require-pragma' ] : [];
+
+// Get the files and directories to format and convert them to globs
+let fileArgs = getFileArgsFromCLI();
+if ( fileArgs.length === 0 ) {
+	fileArgs = [ '.' ];
+}
+
+// Converts `foo/bar` directory to `foo/bar/**/*.js`
+const globArgs = dirGlob( fileArgs, { extensions: [ 'js' ] } );
+
+const result = spawn(
+	resolveBin( 'prettier' ),
+	[ '--write', ...configArgs, ...ignoreArgs, ...pragmaArgs, ...globArgs ],
+	{ stdio: 'inherit' }
+);
+
+process.exit( result.status );