clangd with coc: where to put the "FastCheckFilter" option?

Question

I am using clangd and clang-tidy with coc in neovim. I just upgraded my clang and now I'm getting warnings for my config.yaml

Diagnostics:
  ClangTidy:
    Add: [
      # ...
    ]
    Remove: [
      # ...
      cert-msc24-c, # alias for bugprone-unsafe-functions
#     ~~~~~~~~~~~~
#     ^ Latency of clang-tidy check 'cert-msc24-c' is not known. It will only run if ClangTidy.FastCheckFilter is Loose or None (clangd-config)
      # ...
    ]
    CheckOptions:
      modernize-use-auto.MinTypeNameLength: 10
      # ...

However I can't figure out where to put this ClangTidy.FastCheckFilter option.

When I put it in CheckOptions, I get no feedback, the warnings don't go away:

Diagnostics:
  ClangTidy:
    Add: [
      # ...
    ]
    Remove: [
      # ...
    ]
    CheckOptions:
      ClangTidy.FastCheckFilter: None
      modernize-use-auto.MinTypeNameLength: 10
      # ...

When I put it in the root, I get a warning

Unknown Config key 'ClangTidy' (clangd-config)

ClangTidy:
  FastCheckFilter: None

Diagnostics:
  # ...

And when I place it into Diagnostics/ClangTidy, I get an error

Property FastCheckFilter is not allowed. (yaml-schema: clangtidy options)

Diagnostics:
  ClangTidy:
    FastCheckFilter: None
    # ...

In no case do the warnings for

Latency of clang-tidy check 'cert-msc24-c' is not known. It will only run if ClangTidy.FastCheckFilter is Loose or None (clangd-config)

and others go away.

I tried finding how to use FastCheckFilter by searching for the term, but google shows only a single hit for a doxygen comment for a struct in clang, which also doesn't tell me how to use it.

The configuration documentation also doesn't list that option.

Edit

I looked at the source code and found this snippet

    /// Controls how clang-tidy will run over the code base.
    ///
    /// The settings are merged with any settings found in .clang-tidy
    /// configuration files with these ones taking precedence.
    struct ClangTidyBlock {
      std::vector<Located<std::string>> Add;
      /// List of checks to disable.
      /// Takes precedence over Add. To enable all llvm checks except include
      /// order:
      ///   Add: llvm-*
      ///   Remove: llvm-include-order
      std::vector<Located<std::string>> Remove;
 
      /// A Key-Value pair list of options to pass to clang-tidy checks
      /// These take precedence over options specified in clang-tidy
      /// configuration files. Example:
      ///   CheckOptions:
      ///     readability-braces-around-statements.ShortStatementLines: 2
      std::vector<std::pair<Located<std::string>, Located<std::string>>>
          CheckOptions;
 
      /// Whether to run checks that may slow down clangd.
      ///   Strict: Run only checks measured to be fast. (Default)
      ///           This excludes recently-added checks we have not timed yet.
      ///   Loose: Run checks unless they are known to be slow.
      ///   None: Run checks regardless of their speed.
      std::optional<Located<std::string>> FastCheckFilter;
    };

It seems that the placement in

Diagnostics:
  ClangTidy:
    FastCheckFilter: None
    # ...

is the correct one. I guess my coc-yaml plugin doesn't know about the new fields. I also added the new InlayHints.BlockEnd field, which it doesn't like. But that one actually works.

But I still get the warnings from the clangd-config linter for the unknown speed.

Answer 1

The warning "Latency of clang-tidy check ... is not known." was added to the repo on 2023-10-20 as part of work on Issue 1337. As of 2023-11-07, the most recent released version is Clang+LLVM-17.0.4, which does not have this change in it. Thus, I think you must be using an unreleased version.

Based on how the change was made in clangd/ConfigFragment.h, the FastCheckFilter key is supposed to be a child of ClangTidy, itself a child of Diagnostics. However, the associated YAML schema has evidently not been updated (in another project; see HighCommander4's answer), so the key is rejected when in its proper place. At this moment, there is only one test of this feature (unittests/ReplayPreambleTests.cpp), and it bypasses YAML parsing. So, as far as I can tell, the warning cannot be suppressed in the bleeding-edge version.

I don't see any already-filed issues on this topic, so you could file one.