Fix fish shell environment variable probing by properly quoting commands

Co-authored-by: chrmarti <[email protected]>

Author: Copilot

src/spec-common/injectHeadless.ts

@@ -849,12 +849,25 @@ async function runUserEnvProbe(userEnvProbe: UserEnvProbe, params: { allowSystem
 
 		// handle popular non-POSIX shells
 		const name = path.posix.basename(systemShellUnix);
-		const command = `echo -n ${mark}; ${cmd}; echo -n ${mark}`;
+		let command = `echo -n ${mark}; ${cmd}; echo -n ${mark}`;
 		let shellArgs: string[];
 		if (/^pwsh(-preview)?$/.test(name)) {
 			shellArgs = userEnvProbe === 'loginInteractiveShell' || userEnvProbe === 'loginShell' ?
 				['-Login', '-Command'] : // -Login must be the first option.
 				['-Command'];
+		} else if (/^fish$/.test(name)) {
+			// Fish shell needs the command to be quoted when using interactive modes
+			// to prevent it from interpreting the -n flag as a shell option
+			const isInteractive = userEnvProbe === 'loginInteractiveShell' || userEnvProbe === 'interactiveShell';
+			if (isInteractive) {
+				command = `'${command.replace(/'/g, `'\\''`)}'`;
+			}
+			shellArgs = [
+				userEnvProbe === 'loginInteractiveShell' ? '-lic' :
+					userEnvProbe === 'loginShell' ? '-lc' :
+						userEnvProbe === 'interactiveShell' ? '-ic' :
+							'-c'
+			];
 		} else {
 			shellArgs = [
 				userEnvProbe === 'loginInteractiveShell' ? '-lic' :

src/test/fishShell.test.ts

@@ -0,0 +1,86 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as assert from 'assert';
+import * as path from 'path';
+import * as crypto from 'crypto';
+
+describe('Fish shell command construction', function () {
+	this.timeout('20s');
+
+	it('should properly quote commands for fish shell in interactive mode', async () => {
+		// Simulate the logic from runUserEnvProbe function
+		const systemShellUnix = '/usr/bin/fish';
+		const name = path.posix.basename(systemShellUnix);
+		const mark = crypto.randomUUID();
+		let command = `echo -n ${mark}; cat /proc/self/environ; echo -n ${mark}`;
+		
+		// Test fish shell detection and command quoting
+		if (/^fish$/.test(name)) {
+			// Fish shell needs the command to be quoted when using interactive modes
+			// to prevent it from interpreting the -n flag as a shell option
+			const isInteractive = true; // simulating 'loginInteractiveShell'
+			if (isInteractive) {
+				command = `'${command.replace(/'/g, `'\\''`)}'`;
+			}
+		}
+		
+		// Verify the command is properly quoted
+		assert.ok(command.startsWith(`'echo -n ${mark};`));
+		assert.ok(command.endsWith(`; echo -n ${mark}'`));
+		assert.ok(command.includes('cat /proc/self/environ'));
+		
+		// Test that the command handles single quotes properly
+		const commandWithQuotes = `echo -n ${mark}; echo 'test'; echo -n ${mark}`;
+		let quotedCommand = commandWithQuotes;
+		if (/^fish$/.test(name)) {
+			quotedCommand = `'${commandWithQuotes.replace(/'/g, `'\\''`)}'`;
+		}
+		
+		// Verify single quotes are properly escaped
+		assert.ok(quotedCommand.includes(`'\\''test'\\''`));
+	});
+
+	it('should not quote commands for fish shell in non-interactive mode', async () => {
+		// Simulate the logic from runUserEnvProbe function
+		const systemShellUnix = '/usr/bin/fish';
+		const name = path.posix.basename(systemShellUnix);
+		const mark = crypto.randomUUID();
+		let command = `echo -n ${mark}; cat /proc/self/environ; echo -n ${mark}`;
+		
+		// Test fish shell detection and command quoting
+		if (/^fish$/.test(name)) {
+			// Fish shell needs the command to be quoted when using interactive modes
+			// to prevent it from interpreting the -n flag as a shell option
+			const isInteractive = false; // simulating 'loginShell' (non-interactive)
+			if (isInteractive) {
+				command = `'${command.replace(/'/g, `'\\''`)}'`;
+			}
+		}
+		
+		// Verify the command is NOT quoted for non-interactive mode
+		assert.ok(!command.startsWith(`'echo -n ${mark};`));
+		assert.ok(!command.endsWith(`; echo -n ${mark}'`));
+		assert.strictEqual(command, `echo -n ${mark}; cat /proc/self/environ; echo -n ${mark}`);
+	});
+
+	it('should not affect non-fish shells', async () => {
+		// Test that other shells are not affected
+		const systemShellUnix = '/bin/bash';
+		const name = path.posix.basename(systemShellUnix);
+		const mark = crypto.randomUUID();
+		let command = `echo -n ${mark}; cat /proc/self/environ; echo -n ${mark}`;
+		const originalCommand = command;
+		
+		// Test non-fish shell
+		if (/^fish$/.test(name)) {
+			// This should not execute for bash
+			command = `'${command.replace(/'/g, `'\\''`)}'`;
+		}
+		
+		// Verify the command is unchanged for non-fish shells
+		assert.strictEqual(command, originalCommand);
+	});
+});