json: fix parsing first array-array element

Previously, the first element inside the array-array didn't contain the
decoded data.

Signed-off-by: Michael Zimmermann <[email protected]>

Author: M1cha

include/data/json.h

@@ -360,11 +360,14 @@ typedef int (*json_append_bytes_t)(const char *bytes, size_t len,
 					.offset = offsetof(struct_, \
 							   len_field_), \
 					{ \
-						.object = { \
-							.sub_descr = \
+						.array = { \
+							.element_descr = \
 								elem_descr_, \
-							.sub_descr_len = \
-							    elem_descr_len_, \
+							.n_elements = \
+								1 + \
+								ZERO_OR_COMPILE_ERROR( \
+									elem_descr_len_ == 1 \
+								), \
 						}, \
 					}, \
 				} }, \

lib/os/json.c

@@ -509,12 +509,18 @@ static int arr_parse(struct json_obj *obj,
 {
 	ptrdiff_t elem_size = get_elem_size(elem_descr);
 	void *last_elem = (char *)field + elem_size * max_elements;
-	size_t *elements = (size_t *)((char *)val + elem_descr->offset);
+	size_t *elements = NULL;
 	struct token value;
 
+	if (val) {
+		elements = (size_t *)((char *)val + elem_descr->offset);
+	}
+
 	__ASSERT_NO_MSG(elem_size > 0);
 
-	*elements = 0;
+	if (elements) {
+		*elements = 0;
+	}
 
 	while (!arr_next(obj, &value)) {
 		if (value.type == JSON_TOK_LIST_END) {
@@ -525,11 +531,13 @@ static int arr_parse(struct json_obj *obj,
 			return -ENOSPC;
 		}
 
-		if (decode_value(obj, elem_descr, &value, field, val) < 0) {
+		if (decode_value(obj, elem_descr, &value, field, NULL) < 0) {
 			return -EINVAL;
 		}
 
-		(*elements)++;
+		if (elements) {
+			(*elements)++;
+		}
 		field = (char *)field + elem_size;
 	}
 

tests/lib/json/src/main.c

@@ -232,8 +232,20 @@ static void test_json_decoding_array_array(void)
 			     &obj_array_array_ts);
 
 	zassert_equal(ret, 1, "Encoding array of object returned no errors");
+	zassert_equal(obj_array_array_ts.objects_array_len, 3, "Array has correct number of items");
+
+	zassert_true(!strcmp(obj_array_array_ts.objects_array[0].objects.name,
+			 "Simón Bolívar"), "String decoded correctly");
+	zassert_equal(obj_array_array_ts.objects_array[0].objects.height, 168,
+		      "Simón Bolívar height decoded correctly");
+
 	zassert_true(!strcmp(obj_array_array_ts.objects_array[1].objects.name,
 			 "Pelé"), "String decoded correctly");
+	zassert_equal(obj_array_array_ts.objects_array[1].objects.height, 173,
+		      "Pelé height decoded correctly");
+
+	zassert_true(!strcmp(obj_array_array_ts.objects_array[2].objects.name,
+			 "Usain Bolt"), "String decoded correctly");
 	zassert_equal(obj_array_array_ts.objects_array[2].objects.height, 195,
 		      "Usain Bolt height decoded correctly");
 }