feat: add convenience methods to convert to/from json (#39)

Author: software-dov

packages/proto-plus/proto/message.py

@@ -21,6 +21,7 @@
 from google.protobuf import descriptor_pb2
 from google.protobuf import message
 from google.protobuf import symbol_database
+from google.protobuf.json_format import MessageToJson, Parse
 
 from proto import _file_info
 from proto import _package_info
@@ -325,6 +326,31 @@ def deserialize(cls, payload: bytes) -> 'Message':
         """
         return cls(cls.pb().FromString(payload))
 
+    def to_json(cls, instance) -> str:
+        """Given a message instance, serialize it to json
+
+        Args:
+            instance: An instance of this message type, or something
+                compatible (accepted by the type's constructor).
+
+        Returns:
+            str: The json string representation of the protocol buffer.
+        """
+        return MessageToJson(cls.pb(instance))
+
+    def from_json(cls, payload) -> 'Message':
+        """Given a json string representing an instance,
+        parse it into a message.
+
+        Args:
+            paylod: A json string representing a message.
+
+        Returns:
+            ~.Message: An instance of the message class against which this
+            method was called.
+        """
+        return cls(Parse(payload, cls()._pb))
+
 
 class Message(metaclass=MessageMeta):
     """The abstract base class for a message.

packages/proto-plus/tests/test_json.py

@@ -0,0 +1,52 @@
+# Copyright (C) 2020  Google LLC
+#
+# Licensed 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
+#
+#     http://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.
+
+import pytest
+
+import proto
+from google.protobuf.json_format import MessageToJson, Parse
+
+
+def test_message_to_json():
+    class Squid(proto.Message):
+        mass_kg = proto.Field(proto.INT32, number=1)
+
+    s = Squid(mass_kg=100)
+    json = Squid.to_json(s)
+    json = json.replace(" ", "").replace("\n", "")
+    assert json == '{"massKg":100}'
+
+
+def test_message_from_json():
+    class Squid(proto.Message):
+        mass_kg = proto.Field(proto.INT32, number=1)
+
+    json = '''{
+    "massKg": 100
+    }    
+    '''
+
+    s = Squid.from_json(json)
+    assert s == Squid(mass_kg=100)
+
+
+def test_message_json_round_trip():
+    class Squid(proto.Message):
+        mass_kg = proto.Field(proto.INT32, number=1)
+
+    s = Squid(mass_kg=100)
+    json = Squid.to_json(s)
+    s2 = Squid.from_json(json)
+
+    assert s == s2