refactor(excmd): pass fargs to Lua for builtin cmds #39528

Problem:
The fallback that tokenizes `eap->arg` by unescaped whitespace (when the
parser doesn't pre-split via `EX_EXPAND` etc.) lives in `nlua_do_ucmd`,
so only user-command callbacks got `eap.fargs`. Builtin commands routed
through `nlua_call_excmd` have to re-parse the args themselves
(e.g. `M.ex_lsp`).

Solution:
- Move the tokenization into `nlua_push_eap` so every Lua handler sees
  `eap.fargs`. Keep only the `EX_NOSPC` override in `nlua_do_ucmd` (the
  `nargs=1`/`?` case which is genuinely user-command-specific).
- Drop the re-parse in `M.ex_lsp`.

runtime/lua/vim/_core/ex_cmd.lua

@@ -174,19 +174,13 @@ local available_subcmds = vim.tbl_keys(actions)
 --- Implements command: `:lsp {subcmd} {name}?`.
 --- @param eap vim._core.ExCmdArgs
 function M.ex_lsp(eap)
-  local fargs = api.nvim_parse_cmd('lsp ' .. eap.args, {}).args
-  if not fargs then
-    return
-  end
-  local subcmd = fargs[1]
+  local subcmd = eap.fargs[1]
   if not vim.list_contains(available_subcmds, subcmd) then
     echo_err(N_('E5800: Invalid :lsp subcommand: %s'):format(subcmd))
     return
   end
 
-  local clients = { unpack(fargs, 2) }
-
-  actions[subcmd](clients)
+  actions[subcmd]({ unpack(eap.fargs, 2) })
 end
 
 --- Completion logic for `:lsp` command

runtime/lua/vim/_core/swapfile.lua

@@ -52,7 +52,7 @@ end
 --- @param items string[] List of swapfile paths.
 function M.select_swap(items)
   vim.ui.select(items, {
-    prompt = N_('Enter number of swap file to use (q or empty cancels):'),
+    prompt = N_('Select a swapfile:'),
     kind = 'swap',
     format_item = format_swap,
   }, function(_, idx)

runtime/lua/vim/_core/tag.lua

@@ -30,7 +30,7 @@ function M.select_tag(eap, extra)
   end
 
   vim.ui.select(items, {
-    prompt = N_('Type number and <Enter> (q or empty cancels):'),
+    prompt = N_('Select a tag:'),
     kind = 'tag',
     format_item = function(m)
       local marker = m.cur and '>' or ' '

src/nvim/lua/executor.c

@@ -223,13 +223,35 @@ static void nlua_push_eap(lua_State *lstate, exarg_T *eap, const cmdmod_T *cmod)
   lua_setfield(lstate, -2, "reg");
 
   // Push pre-split args as "fargs" list, if available (set by the command-line parser).
-  if (eap->args != NULL && eap->argc > 0) {
+  // - Or fall back to splitting `eap->arg` on unescaped whitespace.
+  // - Usercmds with nargs=1/? need different splitting, handled by `nlua_do_ucmd`.
+  if (eap->args != NULL) {
     lua_createtable(lstate, (int)eap->argc, 0);
     for (size_t i = 0; i < eap->argc; i++) {
       lua_pushlstring(lstate, eap->args[i], eap->arglens[i]);
       lua_rawseti(lstate, -2, (int)i + 1);
     }
     lua_setfield(lstate, -2, "fargs");
+  } else {
+    lua_newtable(lstate);
+    size_t length = strlen(eap->arg);
+    if (length > 0) {
+      size_t end = 0;
+      size_t len = 0;
+      int i = 1;
+      char *buf = xcalloc(length, sizeof(char));
+      bool done = false;
+      while (!done) {
+        done = uc_split_args_iter(eap->arg, length, &end, buf, &len);
+        if (len > 0) {
+          lua_pushlstring(lstate, buf, len);
+          lua_rawseti(lstate, -2, i);
+          i++;
+        }
+      }
+      xfree(buf);
+    }
+    lua_setfield(lstate, -2, "fargs");
   }
 }
 
@@ -2336,37 +2358,16 @@ int nlua_do_ucmd(ucmd_T *cmd, exarg_T *eap, bool preview)
     lua_setfield(lstate, -2, "count");
   }
 
-  // Override fargs for user command-specific splitting (nlua_push_eap already set it
-  // for the eap->args!=NULL case, but user commands need special handling for nargs).
+  // Override fargs for nargs=1/? (EX_NOSPC): the whole arg as one element (or empty).
+  // Other cases are handled by `nlua_push_eap`.
   if (cmd->uc_argt & EX_NOSPC) {
-    // nargs=1 or "?": fargs is the whole arg as a single element, or empty.
     lua_createtable(lstate, 1, 0);
     if ((cmd->uc_argt & EX_NEEDARG) || *eap->arg != NUL) {
       lua_pushstring(lstate, eap->arg);
       lua_rawseti(lstate, -2, 1);
     }
     lua_setfield(lstate, -2, "fargs");
-  } else if (eap->args == NULL) {
-    // Pre-split args not available: tokenize eap->arg by unescaped whitespace.
-    lua_newtable(lstate);
-    size_t length = strlen(eap->arg);
-    size_t end = 0;
-    size_t len = 0;
-    int i = 1;
-    char *buf = xcalloc(length, sizeof(char));
-    bool done = false;
-    while (!done) {
-      done = uc_split_args_iter(eap->arg, length, &end, buf, &len);
-      if (len > 0) {
-        lua_pushlstring(lstate, buf, len);
-        lua_rawseti(lstate, -2, i);
-        i++;
-      }
-    }
-    xfree(buf);
-    lua_setfield(lstate, -2, "fargs");
   }
-  // else: eap->args was available, nlua_push_eap already set fargs.
 
   char nargs[2];
   if (cmd->uc_argt & EX_EXTRA) {

test/functional/ex_cmds/lsp_spec.lua

@@ -4,7 +4,6 @@ local t_lsp = require('test.functional.plugin.lsp.testutil')
 
 local clear = n.clear
 local eq = t.eq
-local pcall_err = t.pcall_err
 local exec_lua = n.exec_lua
 
 local create_server_definition = t_lsp.create_server_definition

test/functional/ex_cmds/swapfile_preserve_recover_spec.lua

@@ -172,7 +172,7 @@ describe("preserve and (R)ecover with custom 'directory'", function()
               text = text .. (#chunk >= 2 and chunk[2] or chunk[1])
             end
             -- New ui.select-driven prompt; rich info from format_item.
-            eq(true, text:match('Enter number of swap file to use') ~= nil)
+            eq(true, text:match('Select a swapfile:') ~= nil)
             eq(true, text:match('%.swo') ~= nil)
             eq(true, text:match('%.swp') ~= nil)
             eq(true, text:match('host name:') ~= nil)
@@ -183,7 +183,7 @@ describe("preserve and (R)ecover with custom 'directory'", function()
       else
         screen:expect({
           any = {
-            vim.pesc('Enter number of swap file to use (q or empty cancels):'),
+            vim.pesc('Select a swapfile:'),
             '\n1:.*%.swo',
             '\n2:.*%.swp',
             'host name:',

test/functional/ui/messages_spec.lua

@@ -413,7 +413,7 @@ describe('ui/ext_messages', function()
           for _, chunk in ipairs(msg.content) do
             text = text .. (#chunk >= 2 and chunk[2] or chunk[1])
           end
-          t.matches('^Type number and <Enter> %(q or empty cancels%):\n', text)
+          t.matches('^Select a tag:\n', text)
           t.matches('1: > F%s+help%.txt%s+', text)
         end
         screen.messages = {}

test/old/testdir/test_tagjump.vim

@@ -1241,7 +1241,7 @@ func Test_tselect_listing()
   let l = split(execute("tselect first"), "\n")
   " Nvim: :tselect goes through vim.ui.select().
   let expected =<< [DATA]
-Type number and <Enter> (q or empty cancels):
+Select a tag:
 1:   FS  v    first              Xfoo
 2:   FS  v    first              Xfoo
 [DATA]