How are formatters in CoC configured?

Question

I have been using CoC for a few weeks now and I quite like it. Recently I started configuring the formatting options. I have put "coc.preferences.formatOnSave": true and configured .clang-format file inside my CPP project. Everything worked out of the box and my files were nicely formatted on each save.

I ran into a problem when I wanted to use a feature of clang-format-13 and the default version of clang-format on my system is 11. I looked throughout the CoC wiki and configuration options, and I couldn't find where exactly is the formatter command specified? I guess that running clang-format is a default option for cpp filetypes and that is why it worked out of the box, but I would like to change it so that clang-format-13 is run on each save.

Note: I know I could just symlink clang-format to clang-format-13, but I would like to know how is this handled by CoC under the hood.

Answer 1

Formatting options may be specific per LSP. For example, haskell-language-server expects the formatter options to be set like this in your :CocConfig:

{
    "languageserver": {
        "haskell": {
            "command": "haskell-language-server-wrapper",
            "args": ["--lsp"],
            "rootPatterns": ["*.cabal", "stack.yaml", "cabal.project", "package.yaml", "hie.yaml"],
            "filetypes": ["haskell", "lhaskell"],
            "settings": {
                "formattingProvider": "fourmolu",
                "plugin" : {
                    "fourmolu" :{
                        "config": {
                            "external": true
                        }
                    }
                }
            }
        }
}