Allow specifying the Checks as a list in the yaml config file

[llvmbot]

Bugzilla Link	52086
Version	unspecified
OS	Linux
Reporter	LLVM Bugzilla Contributor
CC	@whisperity

Extended Description

Let's say I want to say:

• Enable all the hicpp-* and cppcoreguidelines-* checks
• With the exception of cppcoreguidelines-narrowing-conversions, because I don't like it
• And without hicpp-avoid-goto because it's just a duplicate of cppcoreguidelines-avoid-goto and I don't want to have to add both in my NOLINT comments.

Currently I can do

---

Checks: 'hicpp-,cppcoreguidelines-,-cppcoreguidelines-narrowing-conversions,-hicpp-avoid-goto'
...

but it's not clear cppcoreguidelines-narrowing-conversions and hicpp-avoid-goto have been disable for very different reasons. I could add a comment before "Checks", but that doesn't work too well when the list gets longer.

As far as I know there is no way to include comments interleaving a YAML string. So it would be nice if "Checks" could be expressed also as a list, so

---

Checks:

• 'hicpp-,cppcoreguidelines-'

I don't like it

• '-cppcoreguidelines-narrowing-conversions'

Duplicate of cppcoreguidelines-avoid-goto

• '-hicpp-avoid-goto'
  ...

could be used.

[whisperity]

(Side note: of course this highlights another issue, namely that NOLINT should also check for aliases when deciding whether to silence a diagnostic?)

[llvmbot]

That would indeed be nice.

The aliases also have the problem that it's not too clear from the docs how they work. I don't think the following question has an answer in the docs:

Is

clang-tidy --checks='-*,hicpp-avoid-goto,cppcoreguidelines-avoid-goto' test.cpp

going to take double the time than

clang-tidy --checks='-*,cppcoreguidelines-avoid-goto' test.cpp

to do the exact same work?

By measuring the wall time of both commands with a (too small to create reliable measurements) test file I would say the answer is no, that clang-tidy is smart enough to notice they are the same and only does the check once. But if I ask --enable-check-profile

clang-tidy --checks='-*,hicpp-avoid-goto,cppcoreguidelines-avoid-goto' --enable-check-profile test.cpp

I get things like

===-------------------------------------------------------------------------===
clang-tidy checks profiling
===-------------------------------------------------------------------------===
Total Execution Time: 0.0001 seconds (0.0001 wall clock)

---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name ---
0.0001 ( 80.3%) 0.0000 ( 0.0%) 0.0001 ( 79.7%) 0.0001 ( 81.2%) hicpp-avoid-goto
0.0000 ( 19.7%) 0.0000 (100.0%) 0.0000 ( 20.3%) 0.0000 ( 18.8%) cppcoreguidelines-avoid-goto
0.0001 (100.0%) 0.0000 (100.0%) 0.0001 (100.0%) 0.0001 (100.0%) Total

Which seem to suggest the aliased checks slows down the process, at least a bit.

[dawagner]

I would also like this. At my work, we've grown a homemade wrapper of clang-tidy that parses a yaml file supporting Checks as a list as well as overlays. Overlays are obsolete now that InheritParentConfig has been introduced but we still can't get rid of the wrapper.

Note that the following would work:

Checks: >-
  *,
  -some-alias,

but we also want to add some comments in there, and that's not possible whereas it can be done if Checks was a yaml list.

[carlosgalvezp]

It is certainly possible to have a list-like with interleaved comments:

Checks: >
  *,
  # Do not run this module,
  -some-module*,
  # Except this check,
  some-module-foo,

The trick is that the comment must end with a comma. Arguably not the most readable/maintainable though.

[carlosgalvezp]

Patch up for review: https://reviews.llvm.org/D147876