patch 7.4.1707

Problem:    Cannot use empty dictionary key, even though it can be useful.
Solution:   Allow using an empty dictionary key.

src/eval.c

@@ -2782,11 +2782,9 @@ get_lval(
 	    if (len == -1)
 	    {
 		/* "[key]": get key from "var1" */
-		key = get_tv_string(&var1);	/* is number or string */
+		key = get_tv_string_chk(&var1);	/* is number or string */
-		if (*key == NUL)
+		if (key == NULL)
 		{
-		    if (!quiet)
-			EMSG(_(e_emptykey));
 		    clear_tv(&var1);
 		    return NULL;
 		}
@@ -5623,11 +5621,9 @@ eval_index(
 
 		    if (len == -1)
 		    {
-			key = get_tv_string(&var1);
+			key = get_tv_string_chk(&var1);
-			if (*key == NUL)
+			if (key == NULL)
 			{
-			    if (verbose)
-				EMSG(_(e_emptykey));
 			    clear_tv(&var1);
 			    return FAIL;
 			}
@@ -7754,11 +7750,9 @@ get_dict_tv(char_u **arg, typval_T *rettv, int evaluate)
 	if (evaluate)
 	{
 	    key = get_tv_string_buf_chk(&tvkey, buf);
-	    if (key == NULL || *key == NUL)
+	    if (key == NULL)
 	    {
 		/* "key" is NULL when get_tv_string_buf_chk() gave an errmsg */
-		if (key != NULL)
-		    EMSG(_(e_emptykey));
 		clear_tv(&tvkey);
 		goto failret;
 	    }

src/hashtab.c

@@ -468,8 +468,7 @@ hash_hash(char_u *key)
     char_u	*p;
 
     if ((hash = *key) == 0)
-	return (hash_T)0;	/* Empty keys are not allowed, but we don't
+	return (hash_T)0;
-				   want to crash if we get one. */
     p = key + 1;
 
     /* A simplistic algorithm that appears to do very well.

src/testdir/test_expr.vim

@@ -36,3 +36,17 @@ func Test_version()
   call assert_false(has('patch-9.1.0'))
   call assert_false(has('patch-9.9.1'))
 endfunc
+
+func Test_dict()
+  let d = {'': 'empty', 'a': 'a', 0: 'zero'}
+  call assert_equal('empty', d[''])
+  call assert_equal('a', d['a'])
+  call assert_equal('zero', d[0])
+  call assert_true(has_key(d, ''))
+  call assert_true(has_key(d, 'a'))
+
+  let d[''] = 'none'
+  let d['a'] = 'aaa'
+  call assert_equal('none', d[''])
+  call assert_equal('aaa', d['a'])
+endfunc

src/version.c

@@ -748,6 +748,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1707,
 /**/
     1706,
 /**/