ultimate-vim/sources_non_forked/ale/ale_linters/c/clangd.vim

" Author: Andrey Melentyev <andrey.melentyev@protonmail.com>
" Description: Clangd language server

call ale#Set('c_clangd_executable', 'clangd')
call ale#Set('c_clangd_options', '')

function! ale_linters#c#clangd#GetProjectRoot(buffer) abort
    let l:project_root = ale#path#FindNearestFile(a:buffer, 'compile_commands.json')

    return !empty(l:project_root) ? fnamemodify(l:project_root, ':h') : ''
endfunction

function! ale_linters#c#clangd#GetCommand(buffer) abort
    return '%e' . ale#Pad(ale#Var(a:buffer, 'c_clangd_options'))
endfunction

call ale#linter#Define('c', {
\   'name': 'clangd',
\   'lsp': 'stdio',
\   'executable': {b -> ale#Var(b, 'c_clangd_executable')},
\   'command': function('ale_linters#c#clangd#GetCommand'),
\   'project_root': function('ale_linters#c#clangd#GetProjectRoot'),
\})