The Frustrating 'xcrun: Error: Invalid Active Developer Path' on MacOS Catalina and Later Versions

When trying to run command-line tools like `git`, you might encounter an error message that reads:

`error: invalid active developer path`

This issue is particularly common among developers working with Xcode, Swift, or other Apple-specific technologies. In this article, we'll dive into the causes of this problem and provide step-by-step solutions to resolve it on MacOS Cataline (10.15) and later versions.

## Causes

1. Missing Developer Tools: One reason for this error is that you haven't installed Xcode's Command Line Tools or they are outdated.

2. Invalid `XCODE_PATH` Environment Variable: Sometimes, the environment variable `PATH` might not be correctly set up to point to your active developer tools.

## Solutions

### 1. Install Developer Tools via Homebrew (Recommended)

If you haven't already installed Xcode and its Command Line Tools using Homebrew, a popular package manager for MacOS, follow these steps:

1. Open Terminal on your Mac.

2. Type `brew doctor` to check if brew is properly set up.

3. If it's not installed, run the following command: `/usr/bin/ruby -e '$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)'`.

4. Once installation completes, restart Terminal.

### 2. Install Developer Tools via Apple's Xcode

1. Open App Store on your Mac.

2. Search for 'Xcode' and click to install if it doesn't show up automatically.

3. Follow the installation prompts until completion.

### 3. Reset `PATH` Environment Variable

Sometimes, manually resetting or removing environment variables can resolve this issue:

1. Quit Terminal completely by right-clicking (or holding Command + Option) on its icon in Dock and selecting 'Quit'.

2. Type `export PATH=$PATH:/usr/bin` into your new Terminal window to temporarily reset the `PATH`.

### 4. Remove Old Xcode or Developer Tools

If none of the above solutions work, try completely removing old versions of Xcode or Command Line Tools:

1. Open Finder and navigate to `/Library/Developer`.

2. Move (don't delete) both 'Xcode' and '.git` directories to a safe location outside of your `~/Library` directory.

3. Restart your Mac.

### 5. Re-Download and Re-Install Xcode

As a last resort, consider completely uninstalling Xcode:

1. Open Terminal in Recovery Mode (hold Shift while booting).

2. Type `sudo rm -rf / Library/Developer && sudo reboot`.

The 'invalid active developer path' error can be frustrating when trying to work with command-line tools on MacOS Catalina and later versions of Mac OS X/macOS. By following these steps, you should be able to resolve this issue easily.

Remember that keeping your development environment up-to-date is crucial for smooth operation, especially if you're working with Apple-specific technologies like Swift or Objective-C.

Xcrun: error: invalid active developer path