`tsgo --build` fails to invalidate incremental cache after dependency update

[rubenferreira97]

When updating dependencies in package.json that introduce breaking type changes, tsgo --build (incremental mode) fails to detect these changes if a tsconfig.tsbuildinfo file already exists. The build reports success despite the presence of type errors.

If the tsconfig.tsbuildinfo file is manually deleted, the compiler correctly identifies and reports the type errors.

Expected Behavior

The TypeScript compiler should detect changes in node_modules (or the program signature of dependencies) and invalidate the relevant parts of the incremental cache, forcing a re-check of affected files.

Actual Behavior

The compiler assumes the project is up-to-date because the local source files' timestamps/hashes haven't changed, ignoring the fact that the external type definitions they depend on have changed.

[rubenferreira97]

@RyanCavanaugh To help with the Needs Investigation tag, I've set up a minimal reproduction repo here: https://github.com/rubenferreira97/tsgo_build_bug

Note: I originally hit this bug with npm dependencies, but I used local dependencies here to make reproduction easier.

[RyanCavanaugh]

Confirmed repro, thanks @rubenferreira97

[rubenferreira97]

@RyanCavanaugh I've been running into a hanging issue that I suspect might be related to this cache invalidation problem, but in my case, it causes the compiler to hang indefinitely rather than just missing type errors.

I usually notice it when switching between local branches where project references are already built, specifically when those branches are using different versions of tsgo.

When I run tsgo --build, if a referenced project has a .tsbuildinfo cache generated by a different version, the compiler might occasionally fail to invalidate it (it hangs and memory goes up).

It doesn't seem to happen every time, so my working theory is that it might only fail when there's a breaking change in the cache format between those specific versions.

It feels like instead of discarding the stale cache in those edge cases, the compiler tries to use it, makes some incorrect assumptions based on the old data, and ends up deadlocked.

I can't confirm this 100% since it relies on cross-branch state and is incredibly hard to reproduce minimally, but it really seems like tsgo --build might sometimes blindly trust an outdated cache file when it shouldn't.

Should I open a new issue for this even though I don't have a solid reproduction yet, or is leaving this context here enough?

Edit: Forgot to mention that clearing node_modules + .tsbuildinfo for all projects (the referenced projects and the root one) and re-running tsgo --build fixes this, but doing that as a workaround is too cumbersome.