"
" manually:
"   setlocal foldexpr=balena_diagnostics_fold#expr(v:lnum)
"   setlocal foldmethod=expr
"   setlocal foldlevel=1
" or as command:
"   command! BalenaDiagnosticsFold call balena_diagnostics_fold#apply()
"

function! s:foldexpr(lnum)
    return getline(a:lnum)=~'^===\s.*\s===$'?'>1':getline(a:lnum)=~'^---\s.*\s---$'?'>2':'='
endfunction

function! balena_diagnostics_fold#expr(lnum) abort
    return s:foldexpr(a:lnum)
endfunction

function! balena_diagnostics_fold#apply() abort
    setlocal
        \ foldmethod=expr
        \ foldexpr=balena_diagnostics_fold#expr(v:lnum)
        \ foldcolumn=auto:9
        \ foldlevel=1
        \ foldenable
endfunction