coc-api-vim-source with Vim9 :def functions

[atitcreate]

The example in coc-api.txt

" vim source for emails
function! coc#source#email#init() abort
  return {
    \ 'priority': 9,
    \ 'shortcut': 'Email',
    \ 'triggerCharacters': ['@']
    \}
endfunction

function! coc#source#email#complete(option, cb) abort
  let items = ['foo@gmail.com', 'bar@yahoo.com']
  call a:cb(items)
endfunction

can also be written as:

" vim source for emails
" In legacy script
def coc#source#email#init(): dict<any>
  return {
    priority: 9,
    shortcut: 'Email',
    triggerCharacters: ['@']
  }
enddef

def coc#source#email#complete(option: dict<any>, Callback: func(list<any>))
  const items = ['foo@gmail.com', 'bar@yahoo.com']
  Callback(items)
enddef

Pitfall(fixed in ef591cb)

If you use the optional function on_complete, you have to return a value to work around Vim(let):E1031: Cannot use void value on api "call_function" shown in :CocOpenLog

def coc#source#email#on_complete(item: dict<any>): number
  echom 'On complete'
  return 0 # Have to return a value
enddef

The api call_function in the log seems to be s:funcs.call_function in autoload/coc/api.vim, which return call(a:method, a:args), and unlike :function which implicitly returns 0, :def implicitly returns void(without a return value), causing E1031

Limitation(resolved in 78c7f47)

Vim9 script style autoload function is not supported

vim9script
# Not supported
# vim source for emails
# In Vim9 script
export def Init(): dict<any>
  return {
    priority: 9,
    shortcut: 'Email',
    triggerCharacters: ['@']
  }
enddef

export def Complete(option: dict<any>, Callback: func(list<any>))
  const items = ['foo@gmail.com', 'bar@yahoo.com']
  Callback(items)
enddef

As function names in Vim9 script must start with a capitial, and coc-api-vim-source only recognizes function names starting with a lowercase letter.

[chemzqm]

If you use the optional function on_complete, you have to return a value to work around Vim(let):E1031: Cannot use void value on api "call_function"

I've made a fix for it.

[atitcreate]

dca0049 doesn't fix the problem. The error message is still shown in CocOpenLog.
s:funcs.call_function could be called somewhere else, as with this workaround patch the error message is gone.

diff --git a/autoload/coc/api.vim b/autoload/coc/api.vim
index 634be87..3490ce3 100644
--- a/autoload/coc/api.vim
+++ b/autoload/coc/api.vim
@@ -253,7 +253,11 @@ function! s:funcs.unsubscribe(...) abort
endfunction

function! s:funcs.call_function(method, args) abort
-  return call(a:method, a:args)
+  if a:method =~# '^coc#source#\w\+#[Oo]n_complete$'
+    call call(a:method, a:args)
+  else
+    return call(a:method, a:args)
+  endif
endfunction

function! s:funcs.call_dict_function(dict, method, args) abort

[chemzqm]

Fixed

[chemzqm]

Added support for vim9script module 78c7f47