[clang] [clang][analyzer] Add test cases for CTU-import failures (PR #188524)

[Arseniy Zaostrovnykh via cfe-commits]

necto wrote:

@steakhal 
> Speaking of hardcoded USRs in the tests, have you explored if we could make a tool/utility that could create these instead of hardcoding these?
> 
> I expect that in the future we might need to change the mangling there, that would be also non backward compatible. An indirection would sidestep these hardcoded USR issues.

I have explored a little and found no easy and portable way. Likely one could use c-index-test or clang_extdef_map. I agree it would make the tests better. Unfortunately, I have no time to do that at the moment.

> I think the way CTU is tested using these thousands of Input files is just some legacy because we didn't have split-file to actually have these input files in a single test file.

> I also dislike the hard-coded USRs, and I think I'll claude something to make this prettier unless you say I shouldn't because you have forks/or downstream patches where such changes would interfere with. In that case I'd of course try not to mess with you.

I agree and would welcome the improvement. It should not be too hard to port downstream patches

@balazske 
> I like adding these tests and improve error reporting. One issue with these tests can be that if the import "silently fails" we can not verify if there was really the expected type of error (or no error), but this is less important. (But I would like more if these cases are somehow shown to the user.) Probably the rename and move part of this change can be moved to another PR. The new failure tests can be moved again to new sub-directory (or have a common name).

I agree here as well, and again for the time constraints I will not be able to demonstrate that the added test cases actually triggering the error path they are supposed to trigger. In one of the follow-ups I would like to actually report diagnostics for these cases (i.e., address the FIXME in  `CrossTranslationUnitContext::emitCrossTUDiagnostics`), unless it is not welcome in the upstream.

I have addressed your comment, @steakhal in

231317175365 fixup! Add test cases for various CTU-import failure modes

And I have renamed the files after your approval. If you approve, I plan to split this PR into two as suggested by @balazske : 
- add a bunch cases for CTU import failures
- move all CTU-related cases into clang/test/Analysis/ctu directory


https://github.com/llvm/llvm-project/pull/188524