Changed default string type to be str

This impacts the following APIs:
  Metadata: Key is always a str, Value is bytes for binary metadata,
    str otherwise
  Call Details: str type
  gRPC method: str type
  hostname/target: str type

1 files changed, 31 insertions, 12 deletions

diff --git a/src/python/grpcio/grpc/_common.py b/src/python/grpcio/grpc/_common.py
index f351bea9e3..4d7d521419 100644
--- a/src/python/grpcio/grpc/_common.py
+++ b/src/python/grpcio/grpc/_common.py
@@ -76,9 +76,37 @@ STATUS_CODE_TO_CYGRPC_STATUS_CODE = {
 }
 
 
-def metadata(application_metadata):
+def encode(s):
+  if isinstance(s, bytes):
+    return s
+  else:
+    return s.encode('ascii')
+
+
+def decode(b):
+  if isinstance(b, str):
+    return b
+  else:
+    try:
+      return b.decode('utf8')
+    except UnicodeDecodeError:
+      logging.exception('Invalid encoding on {}'.format(b))
+      return b.decode('latin1')
+
+
+def cygrpc_metadata(application_metadata):
   return _EMPTY_METADATA if application_metadata is None else cygrpc.Metadata(
-      cygrpc.Metadatum(key, value) for key, value in application_metadata)
+      cygrpc.Metadatum(encode(key), encode(value))
+      for key, value in application_metadata)
+
+
+def application_metadata(cygrpc_metadata):
+  if cygrpc_metadata is None:
+    return ()
+  else:
+    return tuple(
+        (decode(key), value if key[-4:] == b'-bin' else decode(value))
+        for key, value in cygrpc_metadata)
 
 
 def _transform(message, transformer, exception_message):
@@ -101,17 +129,8 @@ def deserialize(serialized_message, deserializer):
                     'Exception deserializing message!')
 
 
-def _encode(s):
-  if isinstance(s, bytes):
-    return s
-  else:
-    return s.encode('ascii')
-
-
 def fully_qualified_method(group, method):
-  group = _encode(group)
-  method = _encode(method)
-  return b'/' + group + b'/' + method
+  return '/{}/{}'.format(group, method)
 
 
 class CleanupThread(threading.Thread):