CRASH: Could not cast value of type 'Observation.ObservationRegistrar' to 'Perception._PerceptionRegistrar'

[iharandreyev]

Description

The error in question happens when I'm trying to test the following feature

import ComposableArchitecture
import Foundation

@ObservableState
enum RemoteResourceState<Value> {
    case none
    case loading
    case loaded(Value)
    case failed(Error)
}

extension RemoteResourceState: Equatable where Value: Equatable {
    static func == (lhs: Self, rhs: Self) -> Bool {
        switch (lhs, rhs) {
        case (.none, .none): return true
        case (.loading, .loading): return true
        case let (.loaded(lhs), .loaded(rhs)):
            return lhs == rhs
        case let (.failed(lhs), .failed(rhs)):
            return "\(lhs)" == "\(rhs)"
        default:
            return false
        }
    }
}

enum RemoteResourceAction<Value> {
    case load
    case succeed(Value)
    case fail(Error)
}

extension RemoteResourceAction: Equatable where Value: Equatable {
    static func == (lhs: Self, rhs: Self) -> Bool {
        switch (lhs, rhs) {
        case (.load, .load): return true
        case let (.succeed(lhs), .succeed(rhs)):
            return lhs == rhs
        case let (.fail(lhs), .fail(rhs)):
            return "\(lhs)" == "\(rhs)"
        default:
            return false
        }
    }
}

struct RemoteResource<Value>: Reducer {
    typealias State = RemoteResourceState<Value>
    typealias Action = RemoteResourceAction<Value>
    
    var body: some ReducerOf<Self> {
        EmptyReducer()
    }
}

with a test below

import XCTest
import ComposableArchitecture
@testable import MyApp

final class RemoteResourceTests: XCTestCase {
    func testLoadFirst() async {
        typealias SUT = RemoteResource<TestResource>
        
        let store = TestStoreOf<SUT>(
            initialState: .none,
            reducer: SUT.init
        )
        
        await store.send(.load) { state in
            state = .loading
        }
    }
}

// MARK: - Helpers

private struct TestResource: Identifiable, Equatable {
    let id: Int = UUID().hashValue
}

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

Test fails with an invalid behavior error

Actual behavior

Test crashes with Could not cast value of type 'Observation.ObservationRegistrar' to 'Perception._PerceptionRegistrar' error in Perception/PerceptionRegistrar.swift:52

Steps to reproduce

Run the code in the description

The Composable Architecture version information

1.10.4

Destination operating system

iOS 15.0

Xcode version information

15.4

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

[iharandreyev]

The issue occurs when I use iOS 17.5 simulator as a test run destination.
When running on iOS 15.5 simulator, there's no crash

[mbrandonw]

Hi @iharandreyev, I am not able to reproduce this. I have run it in a variety of simulators and it all seems to work fine. Can you please provide a project that demonstrates the problem?

I am also going to convert this to a discussion for the time being because it's not clear there is an actual issue with the library. Let's continue the conversation over there.

[iharandreyev]

@mbrandonw Here is a link to a repo where the issue is reproduced.

I now think it may have to do something with the fact I'm using tuist to generate the project.
I had some linking issues (as the repo name suggests), but after updating tuist to 4.14.0, linking issues went away.
However, I do get a weird warning

The following warnings need attention:
 · Invalid product name 'swift-composable-architecture_ComposableArchitecture'. This string must contain only alphanumeric (A-Z,a-z,0-9), and underscore (_) characters.

I don't get this kind of warning with my own framework, that uses similar naming convention (package name is swift-package-name and target name is PackageName)

I see that point free also uses tuist, so you guys may have some knowledge to share that I'm lacking.

[mbrandonw]

Hi @iharandreyev, this is certainly an issue with tuist and linking. We get issues like this quite frequently, but we do not personally use tuist so there isn't much we can do to help. I would suggest posting a question on their GitHub to see if they can help.

[iharandreyev]

@mbrandonw by the way, why is perceptionRegistrar still used when Observation can be imported?
I thought the idea was of perceptionRegistrar was to be a placeholder for observationRegistrar when Observation and iOS 17 are not available.

[mbrandonw]

The point of PerceptionRegistrar is to provide a single interface for observation that works on both iOS 17 and iOS 16 (and lower). It determines at runtime whether or not to call down to ObservationRegistrar, if available, or our back port _PerceptionRegistrar.

[iharandreyev]

Created an issue in the tuist project, hope someone helps

[mbrandonw]

Thanks for doing that!

[Narsail]

@iharandreyev How are you linking ComposableArchitecture to your project? I'm migrating my project to tuist at the moment and I ran into various linking issues as well. What works at the moment (at least with Composable Architecture, I still have other linker issues) is the following setup:

App -> Shared Static Framework -> Dynamic Composable Architecture

That said, I had some weird crashes when I used the LDOtherFlags: "-load_all" which created the issue of having multiple libraries of Composable Architecture linked resulting in weird crashes where casting from and to the same state crashed the app. I had to use "-load_all" to solve a SwiftUI issue that I encountered with my SharedFramework.

[iharandreyev]

You can check the configuration in the sample project repo.
In short: I link TCA as .staticLibrary to the app target using tuist package. Linking it as .dynamicLibrary does not help though.
So in my case, there's no intermediate Shared Static Framework (at least for now, I am planning to move everything TCA-related into some Core package)

[Narsail]

Alright, thanks for opening the issue with Tuist. I will follow it closely 🙏