tsc --watch does not correctly account for added & deleted files

[dgoldstein0]

TypeScript Version: 3.1.1

Search Terms: tsc --watch

Code

// a.ts
declare module 'a' {
  type foo = number;
}

// tsconfig.json
{}

Run tsc --watch --noEmit --project .. Wait for typechecking to complete. cp a.ts b.ts; wait for typechecking to complete again. then touch * and wait for typechecking to run again. then rm b.ts and wait for typechecking to complete again

Expected behavior:

Typechecking should succeed on the first run, should fail with 2 errors on the second run (error TS2300: Duplicate identifier 'foo') since a.ts and b.ts duplicate the same module; the third run should come up with the same results, and the 4th run should succeed.

Actual behavior:

The first run passes as expected, the second run only detects the error in b.ts, the touch * causes the 3rd run to recognize both errors, and then deleting b.ts causes the 4th run to still think there's an error in a.ts.

If I had to guess, tsc --watch is assuming in these file add / remove cases that adding or removing b.ts isn't going to change the type errors it finds in a.ts; this type of error is an example where that's clearly not the case.

Related Issues: couldn't find any

[RyanCavanaugh]

@sheetalkamat I'm inclined to tag Design Limitation but wanted your opinion as well

[sheetalkamat]

I don't think this is by design. Its a bug as in we do not re-retrieve semantic diagnostics of the file which could share the new added augmented module. We need to add that logic to builder/builderState.

[dgoldstein0]

thanks for the quick turnaround! I'll look forward to the fix in TS 3.2 And in the meantime if I find more bugs of this type I'll report them too.