Solving Swift Macro Trust Issues in Xcode Cloud Builds

The Problem with Swift Macros in CI Environments

Swift macros, introduced in Xcode 15 with Swift 5.9, are a powerful feature that enables code generation and compile-time metaprogramming. While they offer excellent developer productivity benefits, they've introduced a new challenge for CI/CD pipelines, particularly in Xcode Cloud.

When you first use a macro locally, Xcode displays a dialog asking you to trust the macro's package before it can be executed. This works fine on your development machine, but becomes problematic in automated environments like Xcode Cloud where there's no way to click "OK" on a dialog box.

If you've tried to build a project using Swift macros in Xcode Cloud, you've likely encountered this frustrating error:

Target must be enabled before it can be used.

A Complete Solution

After some research, I've found a reliable solution that works consistently for Xcode Cloud builds using Swift macros. Here's how to implement it:

Step 1: Create a CI Scripts Folder

First, let's create a dedicated folder for our CI scripts:

1. Right-click your project in Xcode
2. Select "New Group"
3. Name it ci_scripts

Step 2: Create the Post-Clone Script

Next, we'll create a post-clone script that Xcode Cloud will automatically execute after cloning your repository:

1. Right-click the ci_scripts folder
2. Select "New File" → "Empty File"
3. Name it ci_post_clone.sh

Step 3: Add the Script Content

Copy and paste the following code into your new ci_post_clone.sh file:

#!/bin/sh

# Exit on error (-e), undefined vars (-u), and pipeline failures (-o pipefail)
set -euo pipefail

# Disable Xcode macro fingerprint validation to prevent spurious build errors
defaults write com.apple.dt.Xcode IDESkipMacroFingerprintValidation -bool YES

This script does one crucial thing: it disables Xcode's macro fingerprint validation, which is what triggers the trust dialog in the first place.

Step 4: Make the Script Executable

Open Terminal, navigate to your project folder, and run:

chmod +x ci_scripts/ci_post_clone.sh

This command makes your script executable, which is required for Xcode Cloud to run it properly.

Step 5: Commit and Trigger a Build

Commit the new file to your repository and push the changes. This will trigger a new build in Xcode Cloud, which should now complete successfully without the macro trust error.

How It Looks

When properly set up, your project structure should include the CI scripts folder with the post-clone script:

Why This Works

Xcode Cloud automatically executes any script named ci_post_clone.sh located in a ci_scripts directory at the root of your project. Our script modifies the Xcode preferences to disable macro fingerprint validation, effectively bypassing the trust requirement.

The command defaults write com.apple.dt.Xcode IDESkipMacroFingerprintValidation -bool YES changes a specific Xcode preference that controls whether macros need to be explicitly trusted before they can be used.

Security Considerations

Some developers suggest copying the macros.json file (which contains trusted macro fingerprints) from your local machine to the CI environment. However, I believe this approach isn't necessarily more secure than simply disabling validation.

The key consideration here is context: Xcode Cloud runs in a sandboxed environment specifically for building your application. It's not executing arbitrary code on production systems. If you can't trust your development team and your release workflow, you likely have more significant security concerns than macros running in a CI environment.

The Growing Importance of This Solution

As Swift continues to evolve, more and more third-party packages are implementing macros to provide powerful features with minimal boilerplate. For example:

• TranslateKit SDK offers localization macros
• Various logging and debugging libraries are adopting macros
• UI frameworks are using macros to simplify view declarations

This trend will only accelerate as developers discover new use cases for compile-time metaprogramming. Having a reliable solution for handling macros in CI pipelines will become increasingly important for Swift projects.

Now that you've solved the macro trust issue, you can take full advantage of Xcode Cloud's capabilities. In fact, I'll be exploring how to utilize Xcode Cloud for App Store deployments in my next article and accompanying video. This approach can save you valuable time waiting for builds, especially if you ship on multiple Apple platforms (iOS, macOS, visionOS) like I do. Stay tuned for that and happy coding!