Fix Windows command extension resolution

Author: sindresorhus

lib/arguments/command-file.js

@@ -29,8 +29,9 @@ const escapeWindowsCommand = parsed => {
 	// Resolve the file to an absolute path, following its shebang to the interpreter if any
 	const resolvedFile = resolveWithShebang(parsed);
 
-	// A directly executable file is spawned as-is, bypassing `cmd.exe` and its escaping
+	// A directly executable file is spawned by its resolved path, bypassing `cmd.exe` and its escaping
 	if (resolvedFile !== undefined && directlyExecutableRegExp.test(resolvedFile)) {
+		parsed.file = resolvedFile;
 		return parsed;
 	}
 
@@ -74,10 +75,14 @@ const resolveWithShebang = parsed => {
 // Search `PATH` for the command, resolving its Windows executable extension via `PATHEXT`
 const resolvePath = parsed => {
 	const environment = parsed.options.env || process.env;
+	const environmentPathExt = getWindowsEnvironmentValue(environment, 'PATHEXT');
+	const commandExtension = path.extname(parsed.file);
+	// Explicitly named files must be tried verbatim so shebang scripts work even when their extension is excluded from PATHEXT.
+	const pathExt = commandExtension === '' ? environmentPathExt : `${commandExtension}${path.delimiter}${environmentPathExt ?? ''}`;
 	return whichCommandSync(parsed.file, {
 		cwd: parsed.options.cwd,
 		path: getWindowsEnvironmentValue(environment, 'PATH'),
-		pathExt: getWindowsEnvironmentValue(environment, 'PATHEXT'),
+		pathExt,
 	});
 };
 

package.json

@@ -58,7 +58,6 @@
 		"is-plain-obj": "^4.1.0",
 		"is-stream": "^4.0.1",
 		"npm-run-path": "^6.0.0",
-		"path-key": "^4.0.0",
 		"pretty-ms": "^9.3.0",
 		"signal-exit": "^4.1.0",
 		"strip-final-newline": "^4.0.0",
@@ -74,6 +73,7 @@
 		"is-running": "^2.1.0",
 		"log-process-errors": "^12.0.1",
 		"path-exists": "^5.0.0",
+		"path-key": "^4.0.0",
 		"tempfile": "^6.0.1",
 		"tsd": "^0.33.0",
 		"typescript": "^6.0.3",

test/arguments/command-resolution.js

@@ -172,6 +172,26 @@ if (isWindows) {
 		t.is(stdout, 'Hello World');
 	});
 
+	test('Runs a .com executable selected by PATHEXT', async t => {
+		const binaryDirectory = path.join(FIXTURES_DIRECTORY, 'node_modules', '.bin');
+		await mkdir(binaryDirectory, {recursive: true});
+		await cp(process.execPath, path.join(binaryDirectory, 'node-com.com'));
+		const options = {
+			preferLocal: true,
+			localDir: FIXTURES_DIRECTORY,
+			extendEnv: false,
+			env: {
+				Path: path.dirname(process.execPath),
+				PathExt: '.COM',
+			},
+		};
+		const {stdout} = await execa('node-com', ['--version'], options);
+		t.is(stdout, process.version);
+
+		const {stdout: stdoutSync} = execaSync('node-com', ['--version'], options);
+		t.is(stdoutSync, process.version);
+	});
+
 	// A `.cmd` file needs `cmd.exe`, so its forward-slash path must be normalized to
 	// backslashes, otherwise it fails with ENOENT.
 	test('Runs a .cmd file given as a relative POSIX-style subpath', async t => {
@@ -201,6 +221,35 @@ if (isWindows) {
 		t.is(stdoutSync, commandArgument);
 	});
 
+	test('Double-escapes explicit batch files excluded from PATHEXT', async t => {
+		const commandArgument = '"& whoami &"';
+		const options = {
+			extendEnv: false,
+			env: {
+				Path: path.dirname(process.execPath),
+				PathExt: '.EXE',
+			},
+		};
+		const command = path.join(FIXTURES_DIRECTORY, 'echo-shim.cmd');
+		const {stdout} = await execa(command, [commandArgument], options);
+		t.is(stdout, commandArgument);
+
+		const {stdout: stdoutSync} = execaSync(command, [commandArgument], options);
+		t.is(stdoutSync, commandArgument);
+	});
+
+	test('Runs an explicit shebang script excluded from PATHEXT', async t => {
+		const command = path.join(FIXTURES_DIRECTORY, 'echo.js');
+		const options = {
+			extendEnv: false,
+			env: {
+				Path: path.dirname(process.execPath),
+				PathExt: '.EXE',
+			},
+		};
+		await testResolvesCommand(t, command, options);
+	});
+
 	test.serial('Double-escapes metacharacters for preferLocal cmd-shims', async t => {
 		await setupCmdShim();
 		const commandArgument = 'a&whoami';