TestStore changes to shared state, fire publisher in the reducer body

[JOyo246]

Description

I might be missing something here, but when bumping our TCA version and migrating to Sharing 2.0, some of our tests began to fail.

It appears that shared state changes from our teststore assertions bleed back into the reducer?

Here's a repro repo in the UserDefaults case studies

here's a pic of the test output. (Note, i'd expect a single failed action here, but getting 2. Adding a breakpoint reveals that the source of the second fire is the TestStore assertion closure.)

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

TestStore changes to Shared State don't affect the Reducer body

Actual behavior

TestStore changes to Shared State affect the Reducer body

Reproducing project

https://github.com/JOyo246/swift-composable-architecture

The Composable Architecture version information

05601a7

Destination operating system

iOS 18.1

Xcode version information

Xcode 16.2

Swift Compiler version information

6.0.2

[JOyo246]

here's a pic of the test output. (Note, i'd expect a single failed action here, but getting 2. Adding a breakpoint reveals that the source of the second fire is the TestStore assertion closure.)

Also, to "fix this", i can receive both publisher actions, but in our production app, the publisher fires off a chain of events that are asserted, so it would require receiving all of those duplicate actions.

[OguzYuuksel]

Hi, I debugged issue but don't have a fix yet.

in _BoxReference.swift

    private var value: Value {
      willSet {
        subject.send(newValue)
      }
    }

willSet is triggered when below state assertion made.

    await store.send(.counter(.incrementButtonTapped)) { // first willSet is triggered as the result of action.
      $0.counter.$count.withLock { $0 = 1 } // Second willSet is triggered, when we assert.
    }

in TestStore.swift there is expectedStateShouldMatch method that applies mutation to the state. We might need to lose the reference to the Shared value while mutating expectedState not to trigger subject.send

[OguzYuuksel]

I have provided a fix, please see pointfreeco/swift-sharing#120