fix: Add missing mime_type and name in proto conversion utils (#408)

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Fixes the issue when using protoutils, mime type and file name are lost

Author: pwwpche

src/a2a/utils/proto_utils.py

@@ -80,8 +80,14 @@ def file(
         cls, file: types.FileWithUri | types.FileWithBytes
     ) -> a2a_pb2.FilePart:
         if isinstance(file, types.FileWithUri):
-            return a2a_pb2.FilePart(file_with_uri=file.uri)
-        return a2a_pb2.FilePart(file_with_bytes=file.bytes.encode('utf-8'))
+            return a2a_pb2.FilePart(
+                file_with_uri=file.uri, mime_type=file.mime_type, name=file.name
+            )
+        return a2a_pb2.FilePart(
+            file_with_bytes=file.bytes.encode('utf-8'),
+            mime_type=file.mime_type,
+            name=file.name,
+        )
 
     @classmethod
     def task(cls, task: types.Task) -> a2a_pb2.Task:
@@ -500,9 +506,19 @@ def data(cls, data: a2a_pb2.DataPart) -> dict[str, Any]:
     def file(
         cls, file: a2a_pb2.FilePart
     ) -> types.FileWithUri | types.FileWithBytes:
+        common_args = {
+            'mime_type': file.mime_type or None,
+            'name': file.name or None,
+        }
         if file.HasField('file_with_uri'):
-            return types.FileWithUri(uri=file.file_with_uri)
-        return types.FileWithBytes(bytes=file.file_with_bytes.decode('utf-8'))
+            return types.FileWithUri(
+                uri=file.file_with_uri,
+                **common_args,
+            )
+        return types.FileWithBytes(
+            bytes=file.file_with_bytes.decode('utf-8'),
+            **common_args,
+        )
 
     @classmethod
     def task_or_message(

tests/utils/test_proto_utils.py

@@ -22,7 +22,11 @@ def sample_message() -> types.Message:
             types.Part(root=types.TextPart(text='Hello')),
             types.Part(
                 root=types.FilePart(
-                    file=types.FileWithUri(uri='file:///test.txt')
+                    file=types.FileWithUri(
+                        uri='file:///test.txt',
+                        name='test.txt',
+                        mime_type='text/plain',
+                    ),
                 )
             ),
             types.Part(root=types.DataPart(data={'key': 'value'})),
@@ -148,6 +152,8 @@ def test_roundtrip_message(self, sample_message: types.Message):
 
         # Test file part handling
         assert proto_msg.content[1].file.file_with_uri == 'file:///test.txt'
+        assert proto_msg.content[1].file.mime_type == 'text/plain'
+        assert proto_msg.content[1].file.name == 'test.txt'
 
         roundtrip_msg = proto_utils.FromProto.message(proto_msg)
         assert roundtrip_msg == sample_message