patch 8.2.1328: no space allowed before comma in list

Problem:    No space allowed before comma in list.
Solution:   Legacy Vim script allows it. (closes #6577)

src/dict.c

@@ -838,7 +838,7 @@ eval_dict(char_u **arg, typval_T *rettv, evalarg_T *evalarg, int literal)
 		: eval1(arg, &tvkey, evalarg)) == FAIL)	// recursive!
 	    goto failret;
 
-	// The colon should come right after the key, but this wasn't checked
+	// the colon should come right after the key, but this wasn't checked
 	// previously, so only require it in Vim9 script.
 	if (!vim9script)
 	    *arg = skipwhite(*arg);
@@ -895,7 +895,10 @@ eval_dict(char_u **arg, typval_T *rettv, evalarg_T *evalarg, int literal)
 	}
 	clear_tv(&tvkey);
 
-	// the comma must come after the value
+	// the comma should come right after the value, but this wasn't checked
+	// previously, so only require it in Vim9 script.
+	if (!vim9script)
+	    *arg = skipwhite(*arg);
 	had_comma = **arg == ',';
 	if (had_comma)
 	{

src/list.c

@@ -1194,6 +1194,9 @@ eval_list(char_u **arg, typval_T *rettv, evalarg_T *evalarg, int do_error)
 	    else
 		clear_tv(&tv);
 	}
+	// Legacy Vim script allowed a space before the comma.
+	if (!vim9script)
+	    *arg = skipwhite(*arg);
 
 	// the comma must come after the value
 	had_comma = **arg == ',';

src/testdir/test_listdict.vim

@@ -23,6 +23,9 @@ func Test_list_create()
   call assert_equal(10, x)
 endfunc
 
+" This was allowed in legacy Vim script
+let s:list_with_spaces = [1 , 2 , 3]
+
 " List slices
 func Test_list_slice()
   let l = [1, 'as''d', [1, 2, function("strlen")], {'a': 1},]
@@ -202,6 +205,10 @@ func Test_dict()
   call assert_fails("let d={'k' : i}", 'E121:')
 endfunc
 
+" This was allowed in legacy Vim script
+let s:dict_with_spaces = {'one' : 1 , 'two' : 2 , 'three' : 3}
+let s:dict_with_spaces_lit = #{one : 1 , two : 2 , three : 3}
+
 " Dictionary identity
 func Test_dict_identity()
   let d = {001: 'asd', 'b': [1, 2, function('strlen')], -1: {'a': 1},}

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1328,
 /**/
     1327,
 /**/