vim-patch:8.2.0614: get ml_get error when deleting a line in 'completefunc' (#19244)

Problem:    Get ml_get error when deleting a line in 'completefunc'. (Yegappan
            Lakshmanan)
Solution:   Lock the text while evaluating 'completefunc'.
https://github.com/vim/vim/commit/ff06f283e3e4b3ec43012dd3b83f8454c98f6639

Fix a mistake in the porting of patch 8.1.0098.
Cherry-pick Test_run_excmd_with_text_locked() from patch 8.2.0270.
Cherry-pick test_gf.vim changes from patch 8.2.0369.
Cherry-pick message change from later patches.

1 files changed, 11 insertions, 8 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 8d267f6a9e..2775fd4778 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -1062,6 +1062,11 @@ static void f_complete(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     return;
   }
 
+  const int save_textlock = textlock;
+  // "textlock" is set when evaluating 'completefunc' but we can change text
+  // here.
+  textlock = 0;
+
   // Check for undo allowed here, because if something was already inserted
   // the line was already saved for undo and this check isn't done.
   if (!undo_allowed(curbuf)) {
@@ -1070,15 +1075,13 @@ static void f_complete(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 
   if (argvars[1].v_type != VAR_LIST) {
     emsg(_(e_invarg));
-    return;
-  }
-
-  const colnr_T startcol = tv_get_number_chk(&argvars[0], NULL);
-  if (startcol <= 0) {
-    return;
+  } else {
+    const colnr_T startcol = tv_get_number_chk(&argvars[0], NULL);
+    if (startcol > 0) {
+      set_completion(startcol - 1, argvars[1].vval.v_list);
+    }
   }
-
-  set_completion(startcol - 1, argvars[1].vval.v_list);
+  textlock = save_textlock;
 }
 
 /// "complete_add()" function