Migration to 1.8 & 1.9.x Fails Documentation Builds

[xaverlutz]

Description

Hi,

after migrating our app to 1.8 and adjusting the Destination enums, we are unable to build the documentation using either Xcode or the xcodebuild command. The error can be seen in the image below.

The error is from my dummy project, as I wanted to verify if we migrated something wrong. The project can be accessed at this link.

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

No response

Actual behavior

No response

Steps to reproduce

1. Migrate an app to v1.8 & use a destination enum reducer
2. Try to build the documentation (either with Xcode or xcodebuild command)

The Composable Architecture version information

1.8 & 1.9.2

Destination operating system

iOS 17.0

Xcode version information

Version 15.3 (15E204a)

Swift Compiler version information

1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)

[mbrandonw]

Hi @xaverlutz, are you sure this is a TCA-specific issue? It seems more likely that it's a Swift/DocC bug where docs fail to build anytime a macro is involved that generates inner types. Can you try reproducing the problem in a fresh project without TCA involved, and if you succeed then I think this needs to be filed with Apple. I'm not sure there is much we can do to fix this.

[mbrandonw]

Hi @xaverlutz, I'm going to move this to a discussion since I'm not sure it's actually a TCA-specific issue. Sounds like a general Swift/macro issue. Please let us know if you uncover anything new.

[rszczepanski]

Hi @mbrandonw,
unfortunately I have the same problem as @xaverlutz.

Based on your suggestion I've created a test project (here) with a macro package that just adds an inner type and an additional macro that adds a type to the inner type.
All this seems to be building the documentation correctly via Xcode 15.3.

As soon as the TCA is introduced with the Destination/Path enums and the State/Action types are used, the documentation doesn't build anymore with the same errors as above.

Of course this still doesn't rule out that it is an issue with Swift/DocC, so I hope you might have a lead on what we should might try next.

[mbrandonw]

Hi @rszczepanski, I would continue adding more features to your @OuterMacro until things break. Perhaps you need to add a protocol conformance such that the inner type satisfies a protocol requirement. Or maybe you need to add multiple inner types and a computed property. I would imagine that if you keep adding things that @Reducer does then eventually DocC will break.

And I just doubt there is anything that we are doing in TCA that should be breaking DocC. As a matter of principle that just shouldn't be possible, and so it seems more likely that this is just a bug with macros and DocC.

By the way, the repro of this problem is far simpler than using Destination reducers. Just this breaks DocC:

@Reducer
struct TestStruct {}

I think this makes it even more clear that this is a DocC issue, and so it should be possible to get a minimal reproducible project to share with Apple.

[stensmir]

Hi! Are there any updates on resolving this issue? The problem still persists and DocC is still broken. It's really upsetting. Has anyone found a solution by any chance?

[stephencelis]

It appears that Apple is tracking some bugs internally: swiftlang/swift-docc#849

I think the best bet is to continue to repro using small examples that can be filed with Apple.

[Alexminator99]

Hi!! Still having the same issue with Xcode 16. @stensmir did you manage to get solution?

[fruitcoder]

Well the only workaround right now seems to be: expand the macro and copy the generated Action/State enums in your codebase

[xaverlutz]

It seems like Xcode 16.3 fixes this issue.