Improve error handling and tests w.r.t. codecs

Add function kafka.protocol.create_message_set() that takes a list of
payloads and a codec and returns a message set with the desired encoding.

Introduce kafka.common.UnsupportedCodecError, raised if an unknown codec
is specified.

Include a test for the new function.

1 files changed, 58 insertions, 6 deletions

diff --git a/test/test_protocol.py b/test/test_protocol.py
index 854a439..2089f48 100644
--- a/test/test_protocol.py
+++ b/test/test_protocol.py
@@ -1,23 +1,30 @@
+import contextlib
+from contextlib import contextmanager
 import struct
 import unittest2
 
+import mock
+from mock import sentinel
+
 from kafka import KafkaClient
 from kafka.common import (
     OffsetRequest, OffsetCommitRequest, OffsetFetchRequest,
     OffsetResponse, OffsetCommitResponse, OffsetFetchResponse,
     ProduceRequest, FetchRequest, Message, ChecksumError,
-    ConsumerFetchSizeTooSmall, ProduceResponse, FetchResponse,
-    OffsetAndMessage, BrokerMetadata, PartitionMetadata,
-    TopicAndPartition, KafkaUnavailableError, ProtocolError,
-    LeaderUnavailableError, PartitionUnavailableError
+    ConsumerFetchSizeTooSmall, ProduceResponse, FetchResponse, OffsetAndMessage,
+    BrokerMetadata, PartitionMetadata, TopicAndPartition, KafkaUnavailableError,
+    ProtocolError, LeaderUnavailableError, PartitionUnavailableError,
+    UnsupportedCodecError
 )
 from kafka.codec import (
     has_snappy, gzip_encode, gzip_decode,
     snappy_encode, snappy_decode
 )
+import kafka.protocol
 from kafka.protocol import (
-    create_gzip_message, create_message, create_snappy_message, KafkaProtocol,
-    ATTRIBUTE_CODEC_MASK, CODEC_GZIP, CODEC_SNAPPY
+    ATTRIBUTE_CODEC_MASK, CODEC_NONE, CODEC_GZIP, CODEC_SNAPPY, KafkaProtocol,
+    create_message, create_gzip_message, create_snappy_message,
+    create_message_set
 )
 
 class TestProtocol(unittest2.TestCase):
@@ -691,3 +698,48 @@ class TestProtocol(unittest2.TestCase):
             OffsetFetchResponse(topic = 'topic1', partition = 2, offset = 4, error = 0, metadata = "meta"),
             OffsetFetchResponse(topic = 'topic1', partition = 4, offset = 8, error = 0, metadata = "meta"),
         ]))
+
+    @contextmanager
+    def mock_create_message_fns(self):
+        patches = contextlib.nested(
+            mock.patch.object(kafka.protocol, "create_message",
+                              return_value=sentinel.message),
+            mock.patch.object(kafka.protocol, "create_gzip_message",
+                              return_value=sentinel.gzip_message),
+            mock.patch.object(kafka.protocol, "create_snappy_message",
+                              return_value=sentinel.snappy_message),
+        )
+
+        with patches:
+            yield
+
+    def test_create_message_set(self):
+        messages = [1, 2, 3]
+
+        # Default codec is CODEC_NONE. Expect list of regular messages.
+        expect = [sentinel.message] * len(messages)
+        with self.mock_create_message_fns():
+            message_set = create_message_set(messages)
+        self.assertEqual(message_set, expect)
+
+        # CODEC_NONE: Expect list of regular messages.
+        expect = [sentinel.message] * len(messages)
+        with self.mock_create_message_fns():
+            message_set = create_message_set(messages, CODEC_NONE)
+        self.assertEqual(message_set, expect)
+
+        # CODEC_GZIP: Expect list of one gzip-encoded message.
+        expect = [sentinel.gzip_message]
+        with self.mock_create_message_fns():
+            message_set = create_message_set(messages, CODEC_GZIP)
+        self.assertEqual(message_set, expect)
+
+        # CODEC_SNAPPY: Expect list of one snappy-encoded message.
+        expect = [sentinel.snappy_message]
+        with self.mock_create_message_fns():
+            message_set = create_message_set(messages, CODEC_SNAPPY)
+        self.assertEqual(message_set, expect)
+
+        # Unknown codec should raise UnsupportedCodecError.
+        with self.assertRaises(UnsupportedCodecError):
+            create_message_set(messages, -1)