Built-in 'which' command returns non-zero exit code for existing commands

[konard]

Description

The built-in which command in command-stream returns a non-zero exit code even when the command exists in the system PATH.

Steps to Reproduce

1. Install gh CLI tool (GitHub CLI) on macOS via Homebrew
2. Verify gh is available by running gh --version in terminal (works)
3. Use command-stream's built-in which command:

import { $ } from 'command-stream';

const result = await $`which gh`;
console.log(result.code); // Returns non-zero even though gh exists

Expected Behavior

The built-in which command should return exit code 0 when the command is found in PATH.

Actual Behavior

Returns non-zero exit code, incorrectly indicating the command doesn't exist.

Environment

• OS: macOS (Darwin 24.5.0)
• command-stream version: latest
• Node.js/Bun version: Bun

Workaround

Using the system's which command or checking with --version flag works:

// This works correctly
await sh('gh --version', { mirror: false });

Additional Context

The gh command is installed at /opt/homebrew/bin/gh and is accessible from the terminal. Other built-in commands may have similar issues with PATH resolution on macOS systems with Homebrew.

[konard]

Workaround

I found a working workaround for this issue. Instead of using the built-in which command, use the system's /usr/bin/which directly:

// Instead of this (doesn't work with built-in which):
if ((await $`which gh`).code !== 0) {
  console.error('gh not found');
}

// Use this workaround:
try {
  await sh('/usr/bin/which gh', { mirror: false });
} catch {
  console.error('❌ GitHub CLI (gh) not found. Please install it.');
  process.exit(1);
}

This successfully detects commands installed via Homebrew on macOS (like /opt/homebrew/bin/gh).

The { mirror: false } option suppresses the output to keep the terminal clean - it only captures the result internally.