Fix for Serialization errors with JSON adapter

This patch aims to fix the issue#222,
where json data in request can not be serialized
because of TypeError in py3

tests/unit/test_serialize.py

@@ -2,7 +2,8 @@
 import pytest
 
 from vcr.compat import mock
-from vcr.serialize import deserialize
+from vcr.request import Request
+from vcr.serialize import deserialize, serialize
 from vcr.serializers import yamlserializer, jsonserializer
 
 
@@ -83,3 +84,50 @@ def test_deserialize_py2py3_yaml_cassette(tmpdir, req_body, expect):
 def test_serialize_constructs_UnicodeDecodeError(mock_dumps):
     with pytest.raises(UnicodeDecodeError):
         jsonserializer.serialize({})
+
+
+def test_serialize_empty_request():
+    request = Request(
+        method='POST',
+        uri='http://localhost/',
+        body='',
+        headers={},
+    )
+
+    serialize(
+        {'requests': [request], 'responses': [{}]},
+        jsonserializer
+    )
+
+
+def test_serialize_json_request():
+    request = Request(
+        method='POST',
+        uri='http://localhost/',
+        body="{'hello': 'world'}",
+        headers={},
+    )
+
+    serialize(
+        {'requests': [request], 'responses': [{}]},
+        jsonserializer
+    )
+
+
+def test_serialize_binary_request():
+    msg = "Does this HTTP interaction contain binary data?"
+
+    request = Request(
+        method='POST',
+        uri='http://localhost/',
+        body=b'\x8c',
+        headers={},
+    )
+
+    try:
+        serialize(
+            {'requests': [request], 'responses': [{}]},
+            jsonserializer
+        )
+    except (UnicodeDecodeError, TypeError) as exc:
+        assert msg in str(exc)

vcr/serialize.py

@@ -50,7 +50,7 @@ def deserialize(cassette_string, serializer):
 
 def serialize(cassette_dict, serializer):
     interactions = ([{
-        'request': request._to_dict(),
+        'request': compat.convert_to_unicode(request._to_dict()),
         'response': compat.convert_to_unicode(response),
     } for request, response in zip(
         cassette_dict['requests'],

vcr/serializers/compat.py

@@ -37,19 +37,43 @@ def convert_body_to_bytes(resp):
     return resp
 
 
+def _convert_string_to_unicode(string):
+    """
+    If the string is bytes, decode it to a string (for python3 support)
+    """
+    result = string
+
+    try:
+        if string is not None and not isinstance(string, six.text_type):
+            result = string.decode('utf-8')
+    except (TypeError, UnicodeDecodeError, AttributeError):
+        # Sometimes the string actually is binary or StringIO object,
+        # so if you can't decode it, just give up.
+        pass
+
+    return result
+
+
 def convert_body_to_unicode(resp):
     """
-    If the request body is bytes, decode it to a string (for python3 support)
+    If the request or responses body is bytes, decode it to a string
+    (for python3 support)
     """
-    try:
-        if not isinstance(resp['body']['string'], six.text_type):
-            resp['body']['string'] = resp['body']['string'].decode('utf-8')
-    except (KeyError, TypeError, UnicodeDecodeError):
-        # The thing we were converting either wasn't a dictionary or didn't
-        # have the keys we were expecting.  Some of the tests just serialize
-        # and deserialize a string.
+    if type(resp) is not dict:
+        # Some of the tests just serialize and deserialize a string.
+        return _convert_string_to_unicode(resp)
+    else:
+        body = resp.get('body')
+
+        if body is not None:
+            try:
+                body['string'] = _convert_string_to_unicode(
+                    body['string']
+                )
+            except (KeyError, TypeError, AttributeError):
+                # The thing we were converting either wasn't a dictionary or
+                # didn't have the keys we were expecting.
+                # For example request object has no 'string' key.
+                resp['body'] = _convert_string_to_unicode(body)
 
-        # Also, sometimes the thing actually is binary, so if you can't decode
-        # it, just give up.
-        pass
     return resp

vcr/serializers/jsonserializer.py

@@ -9,16 +9,21 @@ def deserialize(cassette_string):
 
 
 def serialize(cassette_dict):
+    error_message = (
+        "Does this HTTP interaction contain binary data? "
+        "If so, use a different serializer (like the yaml serializer) "
+        "for this request?"
+    )
+
     try:
         return json.dumps(cassette_dict, indent=4)
-    except UnicodeDecodeError as original:
+    except UnicodeDecodeError as original: # py2
         raise UnicodeDecodeError(
             original.encoding,
             b"Error serializing cassette to JSON",
             original.start,
             original.end,
-            original.args[-1] +
-            ("Does this HTTP interaction contain binary data? "
-             "If so, use a different serializer (like the yaml serializer) "
-             "for this request?")
+            original.args[-1] + error_message
         )
+    except TypeError as original: # py3
+        raise TypeError(error_message)