Add auto-formatting support for clang-tidy fixes

[sean-mcmanus]

Some clang-tidy fix types such as for readability-braces-around-statements generates fixes that need to be formatted in order to give acceptable results (otherwise, } will have no indentation). Potentially, we just run the currently configured formatting on the lines that are changed.

One workaround is to add --format-style= to C_Cpp.codeAnalysis.clangTidy.args if clang-format style formatting is desired. Or add FormatStyle to a .clang-tidy file. UPDATE: The workaround doesn't work.

UPDATE: I noticed with readability-else-after-return it is desirable to format the entire range, but the fix only applies it to the start/end lines...not sure if there's a way to improve that.

[sean-mcmanus]

I'm seeing FormatStyle: file not working in .clang-tidy with readability-braces-around-statements. I'll file a clang-tidy bug later.

[sean-mcmanus]

I've filed bug llvm/llvm-project#55569 ...it seems like we could work around that via doing a separate format range though.

[sean-mcmanus]

They said it's by design for --export-fixes to not format.

[H-G-Hristov]

This should be optional. Maybe even popup a dialog to ask for reformatting, so that the user can review the clang-tidy changes before applying the formatting. In any case I tried today the auto-fix feature and I guess Clang-Tidy generates invalid code by adding \ to "%s" such as: \"%s\".

[sean-mcmanus]

@H-G-Hristov Yeah, a setting to disable it sounds good. Do you have repro steps for the invalid `"%s" code? It may be a bug with our processing.

[Zingam]

@H-G-Hristov Yeah, a setting to disable it sounds good. Do you have repro steps for the invalid `"%s" code? It may be a bug with our processing.

@sean-mcmanus Sorry for the delay. I have filed some details here: llvm/llvm-project#56669