LocalizedStringKey.formatted(locale:tableName:bundle:comment:) crash

[vladyslavsosiuk]

Description

LocalizedStringKey.formatted(locale:tableName:bundle:comment:) crashes with :

Could not cast value of type 'SwiftUI.LocalizedStringKey.FormatArgument.Token' (0x1e8d39410) to 'NSFormatter' (0x1169d9e08).
on the line 608

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

There is no crash

Actual behavior

The library crashes:

Steps to reproduce

Run this code:

struct ContentView: View {
    var body: some View {
        ForEach(
            [
                TextState(
//                    "Hello world"
                    "Hello \(Text("world"))" // Text interpolation into the LocalizedStringKey crashes
                )
            ],
            id: \.self
        ) {
            Text(
                $0
            )
        }
    }
}

SwiftUI Navigation version information

07a99a9

Destination operating system

iOS 18.0

Xcode version information

Xcode 15.4

Swift Compiler version information

swift-driver version: 1.87.3 Apple Swift version 5.9.2 (swiftlang-5.9.2.2.56 clang-1500.1.0.2.5)
Target: arm64-apple-macosx14.0

[mbrandonw]

Hi @vladyslavsosiuk, ideally this would not crash, and if there's an easy fix we will happily accept a PR. However, we do not think it is ever correct to interpolate Text into a TextState. The whole reason for TextState to exist is to be Equatable and allow for testing. The Text type, while Equatable, does not have a straightforward conformance and is completely untestable.

And so if you do not need testability from your domain, you can just use Text entirely and forget about TextState. And if you do need testability, then you can use TextState and should not use Text at all.

[vladyslavsosiuk]

Hi @mbrandonw, thank you for the detailed reply. That makes sense. I just wanted to raise awareness about the crash

[stephencelis]

Going to close this for now since it's not how the library is intended to be used, but if you can share a crash from real world use we can definitely take a closer look!