fix(input): lua function completion

lua/dressing/input.lua

@@ -164,7 +164,20 @@ M.completefunc = function(findstart, base)
     local pieces = split(completion, ",")
     if pieces[1] == "custom" or pieces[1] == "customlist" then
       local vimfunc = pieces[2]
-      local ret = vim.fn[vimfunc](base, base, vim.fn.strlen(base))
+      local ret
+      if vim.startswith(vimfunc, "v:lua.") then
+        local load_func = string.format("return %s(...)", vimfunc:sub(7))
+        local luafunc, err = loadstring(load_func)
+        if not luafunc then
+          vim.api.nvim_err_writeln(
+            string.format("Could not find completion function %s: %s", vimfunc, err)
+          )
+          return {}
+        end
+        ret = luafunc(base, base, vim.fn.strlen(base))
+      else
+        ret = vim.fn[vimfunc](base, base, vim.fn.strlen(base))
+      end
       if pieces[1] == "custom" then
         ret = split(ret, "\n")
       end

tests/manual/completion.lua

@@ -18,6 +18,14 @@ local cases = {
     prompt = "Complete customlist: ",
     completion = "customlist,CustomCompleteList",
   },
+  {
+    prompt = "Complete custom lua: ",
+    completion = "custom,v:lua.custom_complete_func",
+  },
+  {
+    prompt = "Complete customlist: ",
+    completion = "customlist,v:lua.custom_complete_list",
+  },
 }
 
 vim.cmd([[
@@ -30,6 +38,14 @@ function! CustomCompleteList(arglead, cmdline, cursorpos)
 endfunction
 ]])
 
+function _G.custom_complete_func(arglead, cmdline, cursorpos)
+  return "first\nsecond\nthird"
+end
+
+function _G.custom_complete_list(arglead, cmdline, cursorpos)
+  return { "first", "second", "third" }
+end
+
 local function next()
   local opts = cases[idx]
   if opts then