SPM Build Tool Plugin excessively runs causing recompilation

[Brett-Best]

I use https://github.com/liamnichols/xcstrings-tool, this essentially takes in inputs of *.xcstring and outputs *.swift.
Unfortunately, this is having a large impact on incremental builds where for some reason the build tool plugin runs every time.
This invalidates already compiled SPM targets leading to a large incremental compile time of >100 seconds in a project I work on.

This issue can be reproduced using https://github.com/liamnichols/xcstrings-tool-demo.

I also notice that the CompileXCStrings job runs on every incremental build as well.

I've tested this using Xcode 16.2 and using Xcode 16.2 with latest main of swiftlang/swift-build at time of posting.

CC: @dschaefer2

Build DogTracker_2025-02-03T05-22-22.txt
Build DogTracker_2025-02-03T05-22-36.txt

[dschaefer2]

We'll start investigating this with the swift-package-manager.

[bcardarella]

Is there any update on this yet? We've seen re-build times go from seconds to well over 20 minutes due to what we suspect is this issue.

[dschaefer2]

The example project is an Xcode project. We only deal with command line SwiftPM issues on GitHub. Can you reproduce this issue with a SwiftPM package?