AVRO-4135: [C] full type name for json encoded unions

Like java use the full type name when encoding the types for unions.
This to prevent ambiguities when decoding this json encoded field back
to avro using for example the java library.

Author: steven-aerts

lang/c/src/value-json.c

@@ -337,10 +337,12 @@ avro_value_to_json_t(const avro_value_t *value)
 		case AVRO_UNION:
 		{
 			int  disc;
-			avro_value_t  branch;
+			avro_value_t   branch;
 			avro_schema_t  union_schema;
 			avro_schema_t  branch_schema;
-			const char  *branch_name;
+			const char    *branch_name;
+			const char    *namespace;
+			json_t        *full_name_buf = NULL;
 
 			check_return(NULL, avro_value_get_current_branch(value, &branch));
 
@@ -352,26 +354,40 @@ avro_value_to_json_t(const avro_value_t *value)
 			union_schema = avro_value_get_schema(value);
 			branch_schema =
 			    avro_schema_union_branch(union_schema, disc);
+
+			namespace = avro_schema_namespace(branch_schema);
 			branch_name = avro_schema_type_name(branch_schema);
+			if (namespace != NULL) {
+				full_name_buf = json_sprintf("%s.%s", namespace, branch_name);
+				if (full_name_buf == NULL) {
+					avro_set_error("Cannot allocate full name union");
+					return NULL;
+				}
+				branch_name = json_string_value(full_name_buf);
+			}
 
 			json_t  *result = json_object();
 			if (result == NULL) {
 				avro_set_error("Cannot allocate JSON union");
+				json_decref(full_name_buf);
 				return NULL;
 			}
 
 			json_t  *branch_json = avro_value_to_json_t(&branch);
 			if (branch_json == NULL) {
 				json_decref(result);
+				json_decref(full_name_buf);
 				return NULL;
 			}
 
 			if (json_object_set_new(result, branch_name, branch_json)) {
 				avro_set_error("Cannot append branch to union");
 				json_decref(result);
+				json_decref(full_name_buf);
 				return NULL;
 			}
 
+			json_decref(full_name_buf);
 			return result;
 		}
 

lang/c/tests/CMakeLists.txt

@@ -87,3 +87,4 @@ add_avro_test_checkmem(test_avro_1379)
 add_avro_test_checkmem(test_avro_1691)
 add_avro_test_checkmem(test_avro_1906)
 add_avro_test_checkmem(test_avro_1904)
+add_avro_test_checkmem(test_avro_4135)

lang/c/tests/test_avro_4135.c

@@ -0,0 +1,110 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied.  See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <avro.h>
+
+#define check_exit(call) \
+	do { \
+		int  __rc = call; \
+		if (__rc != 0) { \
+			fprintf(stderr, "Unexpected error:\n  %s\n  %s\n", \
+				avro_strerror(), #call); \
+			exit(EXIT_FAILURE); \
+		} \
+	} while (0)
+
+void check_json_encoding(const avro_value_t * val, const char * expected) {
+	char * actual;
+
+	check_exit(avro_value_to_json(val, 1, &actual));
+	if (strcmp(expected, actual) != 0) {
+		fprintf(stderr, "json encoding mismatch\n expected: %s\n actual:  %s\n", expected, actual);
+		exit(EXIT_FAILURE);
+	}
+	free(actual);
+}
+
+int main(int argc, char **argv)
+{
+	const char  *json =
+		"{"
+		"  \"type\": \"record\","
+		"  \"name\": \"r\","
+		"  \"fields\": ["
+		"    { \"name\": \"field\", \"type\": ["
+		"       \"null\","
+		"       \"int\","
+		"       {"
+		"         \"type\": \"record\","
+		"         \"name\": \"r1\","
+		"         \"fields\": []"
+	    "       },"
+		"       {"
+		"         \"type\": \"record\","
+		"         \"name\": \"r2\","
+		"         \"namespace\": \"space\","
+		"         \"fields\": []"
+	    "       }"
+		"     ]}"
+		"  ]"
+		"}";
+
+	avro_schema_t schema = NULL;
+	avro_schema_error_t error;
+
+	(void) argc;
+	(void) argv;
+
+	check_exit(avro_schema_from_json(json, strlen(json), &schema, &error));
+
+	avro_value_iface_t  *iface = avro_generic_class_from_schema(schema);
+	avro_value_t  val;
+	check_exit(avro_generic_value_new(iface, &val));
+
+#define TEST_AVRO_4135 (1)
+       #if TEST_AVRO_4135
+	{
+		avro_value_t  field;
+		avro_value_t  branch;
+		char  *json_encoding;
+
+		avro_value_get_by_index(&val, 0, &field, NULL);
+		check_exit(avro_value_set_branch(&field, 0, &branch));
+		avro_value_set_null(&branch);
+		check_json_encoding(&val, "{\"field\": null}");
+
+		check_exit(avro_value_set_branch(&field, 1, &branch));
+		avro_value_set_int(&branch, 42);
+		check_exit(avro_value_to_json(&val, 1, &json_encoding));
+		check_json_encoding(&val, "{\"field\": {\"int\": 42}}");
+
+		check_exit(avro_value_set_branch(&field, 2, &branch));
+		check_exit(avro_value_to_json(&val, 1, &json_encoding));
+		check_json_encoding(&val, "{\"field\": {\"r1\": {}}}");
+
+		check_exit(avro_value_set_branch(&field, 3, &branch));
+		check_exit(avro_value_to_json(&val, 3, &json_encoding));
+		check_json_encoding(&val, "{\"field\": {\"space.r2\": {}}}");
+	}
+       #endif
+
+	avro_value_decref(&val);
+	avro_schema_decref(schema);
+	return 0;
+}