Fix CLI to avoid waiting for stdin without any input and avoid different outputs

.changeset/orange-dancers-compete.md

@@ -0,0 +1,5 @@
+---
+"stylelint": minor
+---
+
+Changed: CLI to avoid waiting for stdin without any input

.changeset/twelve-ladybugs-mate.md

@@ -0,0 +1,5 @@
+---
+"stylelint": patch
+---
+
+Fixed: CLI to avoid different outputs on empty files and empty stdin

docs/migration-guide/to-16.md

@@ -13,6 +13,20 @@ Node.js 14 has reached end-of-life. We've removed support for it so that we coul
 - 16.13.0
 - 18.0.0
 
+## Changed CLI to avoid waiting for stdin without any input
+
+If you run the CLI without any input files or input from stdin, the CLI immediately exits with some message (help, error, etc.). Before 16.0.0, the CLI waited for input from stdin.
+
+```sh
+# Before 16.0.0
+stylelint
+# waiting for stdin...
+
+# After 16.0.0
+stylelint
+# show help and then exit
+```
+
 ## Changed CLI to print problems to stderr instead of stdout
 
 If you use the CLI to fix a source string by using the [`--fix`](../user-guide/cli.md#--fix) and [`--stdin`](../user-guide/cli.md#--stdin) options, the CLI will print the fixed code to stdout and any problems to stderr.

lib/__tests__/cli.test.mjs

@@ -183,24 +183,22 @@ describe('buildCLI', () => {
 });
 
 describe('CLI', () => {
-	beforeAll(() => {
+	beforeEach(() => {
 		jest.spyOn(process, 'exit').mockImplementation(() => {});
 		jest.spyOn(process.stdout, 'write').mockImplementation(() => {});
 		jest.spyOn(process.stderr, 'write').mockImplementation(() => {});
-		jest.spyOn(process, 'stdin', 'get').mockImplementation(() => Readable.from([Buffer.from('')]));
 		jest.spyOn(console, 'log').mockImplementation(() => {});
 		jest.spyOn(console, 'error').mockImplementation(() => {});
 	});
 
 	afterEach(() => {
+		jest.restoreAllMocks();
 		process.exitCode = undefined;
 	});
 
-	afterAll(() => {
-		jest.restoreAllMocks();
-	});
+	it('no arguments', async () => {
+		jest.spyOn(process, 'stdin', 'get').mockImplementationOnce(() => ({ isTTY: true }));
 
-	it('basic', async () => {
 		await cli([]);
 
 		expect(process.exit).toHaveBeenCalledWith(0);
@@ -223,7 +221,7 @@ describe('CLI', () => {
 	it('--version', async () => {
 		await cli(['--version']);
 
-		expect(process.exitCode).toBeUndefined();
+		expect(process.exit).toHaveBeenCalledWith(0);
 
 		expect(console.log).toHaveBeenCalledTimes(1);
 		expect(console.log).toHaveBeenCalledWith(expect.stringContaining(pkg.version));
@@ -303,19 +301,46 @@ describe('CLI', () => {
 		);
 	});
 
-	it('--stdin', async () => {
+	it('--stdin with any input from stdin', async () => {
+		jest.spyOn(process, 'stdin', 'get').mockImplementationOnce(() => Readable.from([]));
+
 		await cli(['--stdin', '--config', fixturesPath('config-no-empty-source.json')]);
 
 		expect(process.exitCode).toBe(2);
 
 		expect(process.stdout.write).not.toHaveBeenCalled();
 		expect(process.stderr.write).toHaveBeenCalledTimes(1);
-		expect(process.stderr.write).toHaveBeenNthCalledWith(
-			1,
+		expect(process.stderr.write).toHaveBeenCalledWith(
 			expect.stringContaining('Unexpected empty source'),
 		);
 	});
 
+	it('--stdin with no input from stdin', async () => {
+		jest.spyOn(process, 'stdin', 'get').mockImplementationOnce(() => ({ isTTY: true }));
+
+		await cli(['--stdin']);
+
+		expect(process.exitCode).toBe(1);
+
+		expect(process.stdout.write).not.toHaveBeenCalled();
+		expect(process.stderr.write).toHaveBeenCalledTimes(1);
+		expect(process.stderr.write).toHaveBeenCalledWith(
+			expect.stringContaining('You must pass stylelint a `files` glob or a `code` string'),
+		);
+	});
+
+	it('empty input from stdin without --stdin', async () => {
+		jest.spyOn(process, 'stdin', 'get').mockImplementation(() => Readable.from([]));
+
+		await cli(['--config', fixturesPath('config-no-empty-source.json')]);
+
+		expect(process.exitCode).toBe(2);
+
+		expect(process.stdout.write).not.toHaveBeenCalled();
+		expect(process.stderr.write).toHaveBeenCalledTimes(1);
+		expect(process.stderr.write).toHaveBeenCalledWith(expect.stringMatching('no-empty-source'));
+	});
+
 	it('exits with non zero on unfound module in config', async () => {
 		await cli([
 			'--config',
@@ -365,8 +390,8 @@ describe('CLI', () => {
 
 		expect(process.exitCode).toBeUndefined();
 
-		expect(process.stdout.write).toHaveBeenCalledTimes(0);
-		expect(process.stderr.write).toHaveBeenCalledTimes(0);
+		expect(process.stdout.write).not.toHaveBeenCalled();
+		expect(process.stderr.write).not.toHaveBeenCalled();
 	});
 
 	it('--quiet-deprecation-warnings', async () => {
@@ -379,7 +404,7 @@ describe('CLI', () => {
 
 		expect(process.exitCode).toBe(2);
 
-		expect(process.stdout.write).toHaveBeenCalledTimes(0);
+		expect(process.stdout.write).not.toHaveBeenCalled();
 		expect(process.stderr.write).toHaveBeenCalledTimes(1);
 		expect(process.stderr.write.mock.calls[0][0]).toEqual(
 			expect.not.stringContaining('The "color-hex-case" rule is deprecated.'),
@@ -418,7 +443,6 @@ describe('CLI', () => {
 		expect(process.exitCode).toBe(2);
 
 		expect(process.stdout.write).not.toHaveBeenCalled();
-		expect(process.stdout.write).toHaveBeenCalledTimes(0);
 		expect(process.stderr.write).toHaveBeenCalledTimes(1);
 		expect(stripAnsi(process.stderr.write.mock.calls[0][0])).toContain(
 			'Invalid option "--globby-options". The value "wrong" is not valid JSON object.',

lib/cli.mjs

@@ -497,7 +497,7 @@ export default async function main(argv) {
 		return;
 	}
 
-	if (!options.files && !options.code && !stdin) {
+	if (!options.files && !isString(options.code) && !stdin) {
 		showHelp();
 
 		return;
@@ -580,12 +580,18 @@ function parseGlobbyOptions(value) {
 }
 
 /**
- * @returns {Promise<string>}
+ * @returns {Promise<string | undefined>}
  */
 async function getStdin() {
+	const { stdin } = process;
+
+	if (stdin.isTTY) {
+		return undefined;
+	}
+
 	const chunks = [];
 
-	for await (const chunk of process.stdin) {
+	for await (const chunk of stdin) {
 		chunks.push(chunk);
 	}