vim-patch:8.2.0925: getcompletion() does not return command line arguments

Problem:    Getcompletion() does not return command line arguments.
Solution:   Add the "cmdline" option. (Shougo, closes vim/vim#1140)
https://github.com/vim/vim/commit/1f1fd44ef796dd909ff5f3e5288b3fd79294dc71

4 files changed, 22 insertions, 11 deletions

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 5a01724920..b96fc4ac01 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -4449,7 +4449,7 @@ getcompletion({pat}, {type} [, {filtered}])		*getcompletion()*
 		augroup		autocmd groups
 		buffer		buffer names
 		behave		:behave suboptions
-		cmdline		|cmdline-completion|
+		cmdline		|cmdline-completion| result
 		color		color schemes
 		command		Ex command (and arguments)
 		compiler	compilers
@@ -4482,14 +4482,19 @@ getcompletion({pat}, {type} [, {filtered}])		*getcompletion()*
 		user		user names
 		var		user variables
 
-		If {pat} is an empty string then all matches are returned.
-		Otherwise only items matching {pat} are returned. See
-		|wildcards| for the use of special characters in {pat}.
+		If {pat} is an empty string, then all the matches are
+		returned.  Otherwise only items matching {pat} are returned.
+		See |wildcards| for the use of special characters in {pat}.
 
 		If the optional {filtered} flag is set to 1, then 'wildignore'
 		is applied to filter the results.  Otherwise all the matches
 		are returned. The 'wildignorecase' option always applies.
 
+		If {type} is "cmdline", then the |cmdline-completion| result is
+		returned.  For example, to complete the possible values after
+		a ":call" command: >
+			echo getcompletion('call ', 'cmdline')
+<
 		If there are no matches, an empty list is returned.  An
 		invalid value for {type} produces an error.
 
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 3cc71a39f6..d54e49bbd4 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -3134,6 +3134,12 @@ static void f_getcompletion(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   int           options = WILD_SILENT | WILD_USE_NL | WILD_ADD_SLASH
           | WILD_NO_BEEP;
 
+  if (argvars[1].v_type != VAR_STRING) {
+    EMSG2(_(e_invarg2), "type must be a string");
+    return;
+  }
+  const char *const type = tv_get_string(&argvars[1]);
+
   if (argvars[2].v_type != VAR_UNKNOWN) {
     filtered = (bool)tv_get_number_chk(&argvars[2], NULL);
   }
@@ -3147,12 +3153,12 @@ static void f_getcompletion(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     options |= WILD_KEEP_ALL;
   }
 
-  if (argvars[0].v_type != VAR_STRING || argvars[1].v_type != VAR_STRING) {
+  if (argvars[0].v_type != VAR_STRING) {
     EMSG(_(e_invarg));
     return;
   }
 
-  if (strcmp(tv_get_string(&argvars[1]), "cmdline") == 0) {
+  if (strcmp(type, "cmdline") == 0) {
     set_one_cmd_context(&xpc, tv_get_string(&argvars[0]));
     xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
     goto theend;
@@ -3161,10 +3167,9 @@ static void f_getcompletion(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   ExpandInit(&xpc);
   xpc.xp_pattern = (char_u *)tv_get_string(&argvars[0]);
   xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
-  xpc.xp_context = cmdcomplete_str_to_type(
-      (char_u *)tv_get_string(&argvars[1]));
+  xpc.xp_context = cmdcomplete_str_to_type(type);
   if (xpc.xp_context == EXPAND_NOTHING) {
-    EMSG2(_(e_invarg2), argvars[1].vval.v_string);
+    EMSG2(_(e_invarg2), type);
     return;
   }
 
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 35f6503ce4..bc3d29a03f 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -6282,14 +6282,14 @@ int parse_compl_arg(const char_u *value, int vallen, int *complp,
   return OK;
 }
 
-int cmdcomplete_str_to_type(char_u *complete_str)
+int cmdcomplete_str_to_type(const char *complete_str)
 {
     for (int i = 0; i < (int)(ARRAY_SIZE(command_complete)); i++) {
       char *cmd_compl = get_command_complete(i);
       if (cmd_compl == NULL) {
         continue;
       }
-      if (STRCMP(complete_str, command_complete[i]) == 0) {
+      if (strcmp(complete_str, command_complete[i]) == 0) {
         return i;
       }
     }
diff --git a/src/nvim/testdir/test_cmdline.vim b/src/nvim/testdir/test_cmdline.vim
index 39f865144a..a66aee5e02 100644
--- a/src/nvim/testdir/test_cmdline.vim
+++ b/src/nvim/testdir/test_cmdline.vim
@@ -442,6 +442,7 @@ func Test_getcompletion()
   set tags&
 
   call assert_fails('call getcompletion("", "burp")', 'E475:')
+  call assert_fails('call getcompletion("abc", [])', 'E475:')
 endfunc
 
 func Test_shellcmd_completion()