Fix the MappingProxyType error when converting schema to JSON (#930)

* Use the MappingProxyEncoder to encode the JSON

* Use str instead

* Remove unused import

Author: Chris Hoogeboom

src/confluent_kafka/avro/cached_schema_registry_client.py

@@ -19,7 +19,6 @@
 #
 # derived from https://github.com/verisign/python-confluent-schemaregistry.git
 #
-import json
 import logging
 import warnings
 from collections import defaultdict
@@ -213,7 +212,7 @@ def register(self, subject, avro_schema):
         url = '/'.join([self.url, 'subjects', subject, 'versions'])
         # body is { schema : json_string }
 
-        body = {'schema': json.dumps(avro_schema.to_json())}
+        body = {'schema': str(avro_schema)}
         result, code = self._send_request(url, method='POST', body=body)
         if (code == 401 or code == 403):
             raise ClientError("Unauthorized access. Error code:" + str(code))
@@ -253,7 +252,7 @@ def check_registration(self, subject, avro_schema):
         url = '/'.join([self.url, 'subjects', subject])
         # body is { schema : json_string }
 
-        body = {'schema': json.dumps(avro_schema.to_json())}
+        body = {'schema': str(avro_schema)}
         result, code = self._send_request(url, method='POST', body=body)
         if code == 401 or code == 403:
             raise ClientError("Unauthorized access. Error code:" + str(code))
@@ -374,7 +373,7 @@ def get_version(self, subject, avro_schema):
             return version
 
         url = '/'.join([self.url, 'subjects', subject])
-        body = {'schema': json.dumps(avro_schema.to_json())}
+        body = {'schema': str(avro_schema)}
 
         result, code = self._send_request(url, method='POST', body=body)
         if code == 404:
@@ -402,7 +401,7 @@ def test_compatibility(self, subject, avro_schema, version='latest'):
         """
         url = '/'.join([self.url, 'compatibility', 'subjects', subject,
                         'versions', str(version)])
-        body = {'schema': json.dumps(avro_schema.to_json())}
+        body = {'schema': str(avro_schema)}
         try:
             result, code = self._send_request(url, method='POST', body=body)
             if code == 404:

tests/avro/mock_registry.py

@@ -100,13 +100,13 @@ def get_schema_by_id(self, req, groups):
         if not schema:
             return self._create_error("schema not found", 404)
         result = {
-            "schema": json.dumps(schema.to_json())
+            "schema": str(schema)
         }
         return (200, result)
 
     def _get_identity_schema(self, avro_schema):
         # normalized
-        schema_str = json.dumps(avro_schema.to_json())
+        schema_str = str(avro_schema)
         if schema_str in self.schema_cache:
             return self.schema_cache[schema_str]
         self.schema_cache[schema_str] = avro_schema
@@ -150,7 +150,7 @@ def get_version(self, req, groups):
         schema_id = self.registry.get_id_for_schema(subject, avro_schema)
 
         result = {
-            "schema": json.dumps(avro_schema.to_json()),
+            "schema": str(avro_schema),
             "subject": subject,
             "id": schema_id,
             "version": version
@@ -163,7 +163,7 @@ def get_latest(self, req, groups):
         if schema_id is None:
             return self._create_error("Not found", 404)
         result = {
-            "schema": json.dumps(avro_schema.to_json()),
+            "schema": str(avro_schema),
             "subject": subject,
             "id": schema_id,
             "version": version