[clang-tools-extra] [clang-tidy] support query based custom check (PR #131804)

[Balázs Benics via cfe-commits]

steakhal wrote:

> Thank you for the investigation and report! As it appears, someone else too had similar issues ([#159547 (comment)](https://github.com/llvm/llvm-project/pull/159547#issuecomment-3524039290)).
> 
> Since the issue is inside the Tooling library (which clang-tidy is consumer of), it may require some effort and time to fix properly. There is some issues considering weird behavior with compiler database (like #148819, #148814) which we should hopefully fix eventually.

Thank you for these cross-refs.

> If you wish, please open PR with the hotfix; otherwise, I'll try to do it (hopefully before 22th branching take place)

I don't think I have the bandwidth. And now that we disabled the test, it's not urgent for us, and I don't want to impose deadlines or urgency on anyone. It's fine by me if it's eventually fixed, or just worked around in the affected test for now.

> I wonder if changing the name of test file from `main.cpp` to something unique like `clang-tidy-query.cpp` will solve the issue because the algorithm will fail to find flags for non-existent file in `compile_commands.json`

I don't think it changes anything because currently it randomly picks a 0 scored TU - regardless of the file name AFAIK.

https://github.com/llvm/llvm-project/pull/131804