Fix Xcode15.3 (Swift5.10) warning/Swift 6 error: Main actor-isolated class 'XXXTests' has different actor isolation from nonisolated superclass 'XCTestCase'; this is an error in Swift 6

[kntkymt]

Pull Request Type

• Bug fix
• New feature
• Refactoring
• Documentation update
• Chore

Issue for this PR

Nothing

Environment

xcodebuild -version 
Xcode 15.3
Build version 15E204a

swift --version
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

Description

I encountered below warning at main branch.

Main actor-isolated class 'AtomViewContextTests' has different actor isolation from nonisolated superclass 'XCTestCase'; this is an error in Swift 6

Motivation and Context

I'd like to suppress warning. (It will be error on Swift 6, we have to fix it.)

Detail Information

This swift specification might exist from Swift 5.5, According to the statement in SE0316.

A class can only be annotated with a global actor if it has no superclass, the superclass is annotated with the same global actor, or the superclass is NSObject. A subclass of a global-actor-annotated class must be isolated to the same global actor.

However, above warning exist since swift 5.10.

What I did

• I moved @MainActor attribute from XCTestCase to its functions for all tests.
• Fix README.md.

Impact on Existing Code

• Nothing for Sources code
• A little for Tests code (the isolation behavior on testing code might change?)

Screenshot/Video/Gif

[kntkymt]

I didn't add @MainActor to a few functions like testKey since it does not require @MainActor.
What do you think? Should I add @MainActor to preserve current (main branch) isolation behavior?

swiftui-atom-properties/Tests/AtomsTests/Modifier/SelectModifierTests.swift

Line 29 in 1f363e7

func testKey() {

swiftui-atom-properties/Tests/AtomsTests/Core/SubscriptionKeyTests.swift

Line 6 in 1f363e7

func testKeyHashableForSameToken() {

swiftui-atom-properties/Tests/AtomsTests/Modifier/TaskPhaseModifierTests.swift

Line 19 in 1f363e7

func testKey() {

swiftui-atom-properties/Tests/AtomsTests/SnapshotTests.swift

Line 23 in 1f363e7

func testEmptyGraphDescription() {

[ra1028]

@kntkymt
Thanks! Let me investigate it for a bit to know what exactly happens and community direction, and then merge it afterward.

[rasberik]

Checked with same environment, looks good. There are few other warnings in StoreContext, but those better be addressed separately

[ra1028]

Confirmed by @rasberik . Thanks.