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 #10071)

runtime/doc/builtin.txt

@@ -161,7 +161,8 @@ exists_compiled({expr})		Number	|TRUE| if {expr} exists at compile time
 exp({expr})			Float	exponential of {expr}
 expand({expr} [, {nosuf} [, {list}]])
 				any	expand special keywords in {expr}
-expandcmd({expr})		String	expand {expr} like with `:edit`
+expandcmd({string} [, {options}])
+				String	expand {string} like with `:edit`
 extend({expr1}, {expr2} [, {expr3}])
 				List/Dict insert items of {expr2} into {expr1}
 extendnew({expr1}, {expr2} [, {expr3}])
@@ -2293,18 +2294,27 @@ expand({string} [, {nosuf} [, {list}]])				*expand()*
 		Can also be used as a |method|: >
 			Getpattern()->expand()
 
-expandcmd({string})					*expandcmd()*
+expandcmd({string} [, {options}])			*expandcmd()*
 		Expand special items in String {string} like what is done for
 		an Ex command such as `:edit`.  This expands special keywords,
 		like with |expand()|, and environment variables, anywhere in
 		{string}.  "~user" and "~/path" are only expanded at the
 		start.
+
+		The following items are supported in the {options} Dict
+		argument:
+		    errmsg	If set to TRUE, error messages are displayed
+				if an error is encountered during expansion.
+				By default, error messages are not displayed.
+
 		Returns the expanded string.  If an error is encountered
 		during expansion, the unmodified {string} is returned.
+
 		Example: >
 			:echo expandcmd('make %<.o')
-<			make /path/runtime/doc/builtin.o ~
+			make /path/runtime/doc/builtin.o
-
+			:echo expandcmd('make %<.o', {'errmsg': v:true})
+<
 		Can also be used as a |method|: >
 			GetCommand()->expandcmd()
 <

src/evalfunc.c

@@ -1761,7 +1761,7 @@ static funcentry_T global_functions[] =
 			ret_float,	    FLOAT_FUNC(f_exp)},
     {"expand",		1, 3, FEARG_1,	    arg3_string_bool_bool,
 			ret_any,	    f_expand},
-    {"expandcmd",	1, 1, FEARG_1,	    arg1_string,
+    {"expandcmd",	1, 2, FEARG_1,	    arg2_string_dict,
 			ret_string,	    f_expandcmd},
     {"extend",		2, 3, FEARG_1,	    arg23_extend,
 			ret_extend,	    f_extend},
@@ -4152,10 +4152,18 @@ f_expandcmd(typval_T *argvars, typval_T *rettv)
     exarg_T	eap;
     char_u	*cmdstr;
     char	*errormsg = NULL;
+    int		emsgoff = TRUE;
 
-    if (in_vim9script() && check_for_string_arg(argvars, 0) == FAIL)
+    if (in_vim9script()
+	    && (check_for_string_arg(argvars, 0) == FAIL
+		|| check_for_opt_dict_arg(argvars, 1) == FAIL))
 	return;
 
+    if (argvars[1].v_type == VAR_DICT
+	    && dict_get_bool(argvars[1].vval.v_dict, (char_u *)"errmsg",
+								VVAL_FALSE))
+	emsgoff = FALSE;
+
     rettv->v_type = VAR_STRING;
     cmdstr = vim_strsave(tv_get_string(&argvars[0]));
 
@@ -4167,8 +4175,12 @@ f_expandcmd(typval_T *argvars, typval_T *rettv)
     eap.nextcmd = NULL;
     eap.cmdidx = CMD_USER;
 
+    if (emsgoff)
 	++emsg_off;
-    expand_filename(&eap, &cmdstr, &errormsg);
+    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/filepath.c

@@ -3999,7 +3999,7 @@ gen_expand_wildcards(
 
     // When returning FAIL the array must be freed here.
     if (retval == FAIL)
-	ga_clear(&ga);
+	ga_clear_strings(&ga);
 
     *num_file = ga.ga_len;
     *file = (ga.ga_data != NULL) ? (char_u **)ga.ga_data

src/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')
+  if has('unix') && executable('bash')
-    " test for using the shell to expand a command argument
+    " test for using the shell to expand a command argument.
-    call assert_equal('{1..4}', expandcmd('{1..4}'))
+    " 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

src/testdir/test_vim9_builtin.vim

@@ -1020,6 +1020,7 @@ def Test_expandcmd()
   expandcmd('')->assert_equal('')
 
   v9.CheckDefAndScriptFailure(['expandcmd([1])'], ['E1013: Argument 1: type mismatch, expected string but got list<number>', 'E1174: String required for argument 1'])
+  v9.CheckDefAndScriptFailure(['expandcmd("abc", [])'], ['E1013: Argument 2: type mismatch, expected dict<any> but got list<unknown>', 'E1206: Dictionary required for argument 2'])
 enddef
 
 def Test_extend_arg_types()

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4679,
 /**/
     4678,
 /**/