Macro compilation issue in modularized project

[gyulavoros]

Description

I'm looking for guidance on how to integrate TCA with multiple feature modules.

Given that multiple framework targets depend on TCA, project compilation breaks with the following Xcode error:

External macro implementation type 'PerceptionMacros.PerceptibleMacro' could not be found for macro 'Perceptible()'

Project setup:

• Vanilla Xcode project, or xcodeproj generated via XcodeGen
• TCA is added as SPM dependency
• Two framework targets + one app target
• Both framework targets depend on TCA (this breaks macro compilation)
• App target depends on both framework targets

|-- App
|---- FeatureA
|------ TCA
|---- FeatureB
|------ TCA

This setup used to work with older TCA versions (1.11.2 and prior). I have limited knowledge of macro internals and having a hard time to pinpoint what the issue is.

Checklist

• I have determined whether this bug is also reproducible in a vanilla SwiftUI project.
• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

The project compiles.

Actual behavior

Compilation fails with:

External macro implementation type 'PerceptionMacros.PerceptibleMacro' could not be found for macro 'Perceptible()'

Steps to reproduce

I attached a minimal example demonstrating the issue:
ModularizedMacroIssue.zip

The Composable Architecture version information

1.13.0

Destination operating system

iOS 17.5

Xcode version information

Xcode 15.4 (15F31d)

Swift Compiler version information

swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: arm64-apple-macosx14.0

[mbrandonw]

Hi @gyulavoros, this is not an issue with the library per se, and instead most likely an issue with how your project is set up in Xcode. I am going to convert this to a discussion and perhaps someone can help you out over there.

[gyulavoros]

I might be wrong here, as it was a while ago when I was wrangling with this, but I remember that custom Build Configurations could also interfere with macros. In SPM, "Debug" and "Release" are baked in, and the only available configurations. If your application target scheme uses custom build configurations (e.g, "Mock", "Staging", etc.) Xcode breaks and it displays the errors above. Previews don't work either.

What's frustrating, is that you can still compile, build, and run the project on both the simulator or a physical device. However, not having code completion and tripping over hundreds of inline errors is a dealbreaker.

To sum up, keeping the project setup "as vanilla as possible", defining modules as SPM packages, relying on the default "Debug" and "Release" configurations, etc. is the way to go, I can confirm that both Composable Architecture and other macro based dependencies work like a charm.

[rhkrthdud7]

@gyulavoros Hey I just renamed my configuration as Debug / Release and all the macro errors disappeared.
I was struggling for weeks because of this issue, code completion was completely broken.
But you just saved my life thank you. 👍

[DaniilShmoylove]

I want to share my experience of solving the problem. I updated Xcode to 16.1 (16B40) and the problem was solved. I also use SPM and install the dependency inside the package file

[adarhef]

I want to add to this as well.
I use Tuist and I link all my dependencies dynamically. Partly this is because I need Previews to work, and they just don't with Tuist unless dependencies are linked as frameworks.
Everything works fine for the most part, but yesterday I realized Archiving is broken with this same macro error.
Release builds are fine, I can Profile without a problem for example.
I don't know what's special about Archiving for it to act up like this. Build logs are no help.
Would appreciate any pointers

[mbrandonw]

Hi @adarhef, this sounds more like a Tuist problem and so I recommend you start a discussion on that repo to see if they have any suggestions.

[protonjohn]

It's also worth noting that Sources/SwiftNavigation/UIBinding.swift in the swift-navigation project does not import Perception despite using the @Perceptible macro for _UIBindingWrapper, which might be in some way related to Xcode's unhappiness. (It didn't seem to help when I fixed that, though.)

[mbrandonw]

Hi @protonjohn, SwiftNavigation does an @_exported import of Perception, so it should be available to every file in the library.