[rush] v5.139.0 Breaks Incremental Build

[skaldarnar]

Summary

Rush v5.139.0 breaks incremental building, at least in our project setup. On and above that version, every rush build rebuilds all packages, regardless of changes on the filesystem. On v5.138.0 and below, incremental builds work as expected. We are not using the build cache.

Similar to #4394, but not quite the same.

Repro steps

• Install version 5.138.0
• Run rush update && rush build && rush build, builds are cached 🙂
• Update rush.json to 5.104.0
• Run rush update && rush build && rush build, all packages rebuilt 🙁

Details

We are not using the build cache and there are no project-specific rush-project.json files.

rush --debug build shows Incremental strategy: output preservation.

This is happening on a private repo, but I'm happy to provide more information if needed.

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
@microsoft/rush globally installed version?	5.140.1
rushVersion from rush.json?	5.140.1
useWorkspaces from rush.json?	true
Operating system?	Linux
Would you consider contributing a PR?	yes
Node.js version (node -v)?	v20.18.0