vim-patch:8.2.4679: cannot have expandcmd() give an error message for mistakes

Problem:    Cannot have expandcmd() give an error message for mistakes.
Solution:   Add an optional argument to give errors. Fix memory leak when
            expanding files fails. (Yegappan Lakshmanan, closes vim/vim#10071)
2b74b6805b

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

src/nvim/eval.lua

@@ -118,7 +118,7 @@ return {
     exists={args=1, base=1},
     exp={args=1, base=1, float_func="exp"},
     expand={args={1, 3}, base=1},
-    expandcmd={args=1, base=1},
+    expandcmd={args={1, 2}, base=1},
     extend={args={2, 3}, base=1},
     feedkeys={args={1, 2}, base=1},
     file_readable={args=1, base=1, func='f_filereadable'},  -- obsolete

src/nvim/eval/funcs.c

@@ -2058,6 +2058,12 @@ static void f_menu_get(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 static void f_expandcmd(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
   char *errormsg = NULL;
+  bool emsgoff = true;
+
+  if (argvars[1].v_type == VAR_DICT
+      && tv_dict_get_bool(argvars[1].vval.v_dict, "errmsg", kBoolVarFalse)) {
+    emsgoff = false;
+  }
 
   rettv->v_type = VAR_STRING;
   char *cmdstr = xstrdup(tv_get_string(&argvars[0]));
@@ -2071,9 +2077,17 @@ static void f_expandcmd(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   };
   eap.argt |= EX_NOSPC;
 
-  emsg_off++;
-  expand_filename(&eap, &cmdstr, &errormsg);
-  emsg_off--;
+  if (emsgoff) {
+    emsg_off++;
+  }
+  if (expand_filename(&eap, &cmdstr, &errormsg) == FAIL) {
+    if (!emsgoff && errormsg != NULL && *errormsg != NUL) {
+      emsg(errormsg);
+    }
+  }
+  if (emsgoff) {
+    emsg_off--;
+  }
 
   rettv->vval.v_string = cmdstr;
 }

src/nvim/path.c

@@ -1244,7 +1244,7 @@ int gen_expand_wildcards(int num_pat, char **pat, int *num_file, char ***file, i
       add_pat = expand_backtick(&ga, (char *)p, flags);
       if (add_pat == -1) {
         recursive = false;
-        FreeWild(ga.ga_len, ga.ga_data);
+        ga_clear_strings(&ga);
         *num_file = 0;
         *file = NULL;
         return FAIL;

src/nvim/testdir/test_expand.vim

@@ -90,14 +90,26 @@ func Test_expandcmd()
   " Test for expression expansion `=
   let $FOO= "blue"
   call assert_equal("blue sky", expandcmd("`=$FOO .. ' sky'`"))
+  let x = expandcmd("`=axbycz`")
+  call assert_equal('`=axbycz`', x)
+  call assert_fails('let x = expandcmd("`=axbycz`", #{errmsg: 1})', 'E121:')
+  let x = expandcmd("`=axbycz`", #{abc: []})
+  call assert_equal('`=axbycz`', x)
 
   " Test for env variable with spaces
   let $FOO= "foo bar baz"
   call assert_equal("e foo bar baz", expandcmd("e $FOO"))
 
-  if has('unix')
-    " test for using the shell to expand a command argument
-    call assert_equal('{1..4}', expandcmd('{1..4}'))
+  if has('unix') && executable('bash')
+    " test for using the shell to expand a command argument.
+    " only bash supports the {..} syntax
+    set shell=bash
+    let x = expandcmd('{1..4}')
+    call assert_equal('{1..4}', x)
+    call assert_fails("let x = expandcmd('{1..4}', #{errmsg: v:true})", 'E77:')
+    let x = expandcmd('{1..4}', #{error: v:true})
+    call assert_equal('{1..4}', x)
+    set shell&
   endif
 
   unlet $FOO