feat: Set grpc dependencies as optional (#322)

# Description

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Fixes #<issue_number_goes_here> 🦕

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: kthota-g

.github/workflows/unit-tests.yml

@@ -55,7 +55,7 @@ jobs:
         run: |
           echo "$HOME/.cargo/bin" >> $GITHUB_PATH
       - name: Install dependencies
-        run: uv sync --dev --extra sql --extra encryption
+        run: uv sync --dev --extra sql --extra encryption --extra grpc
       - name: Run tests and check coverage
         run: uv run pytest --cov=a2a --cov-report=xml --cov-fail-under=89
       - name: Show coverage summary in log

pyproject.toml

@@ -11,16 +11,11 @@ dependencies = [
   "fastapi>=0.115.2",
   "httpx>=0.28.1",
   "httpx-sse>=0.4.0",
-  "google-api-core>=1.26.0",
   "opentelemetry-api>=1.33.0",
   "opentelemetry-sdk>=1.33.0",
   "pydantic>=2.11.3",
   "sse-starlette",
-  "starlette",
-  "grpcio>=1.60",
-  "grpcio-tools>=1.60",
-  "grpcio_reflection>=1.7.0",
-  "protobuf==5.29.5",
+  "starlette"
 ]
 
 classifiers = [
@@ -42,6 +37,7 @@ mysql = ["sqlalchemy[asyncio,aiomysql]>=2.0.0"]
 sqlite = ["sqlalchemy[asyncio,aiosqlite]>=2.0.0"]
 sql = ["sqlalchemy[asyncio,postgresql-asyncpg,aiomysql,aiosqlite]>=2.0.0"]
 encryption = ["cryptography>=43.0.0"]
+grpc = ["grpcio>=1.60", "grpcio-tools>=1.60", "grpcio_reflection>=1.7.0", "protobuf==5.29.5", "google-api-core>=1.26.0"]
 
 [project.urls]
 homepage = "https://a2a-protocol.org/"

src/a2a/server/request_handlers/__init__.py

@@ -1,9 +1,10 @@
 """Request handler components for the A2A server."""
 
+import logging
+
 from a2a.server.request_handlers.default_request_handler import (
     DefaultRequestHandler,
 )
-from a2a.server.request_handlers.grpc_handler import GrpcHandler
 from a2a.server.request_handlers.jsonrpc_handler import JSONRPCHandler
 from a2a.server.request_handlers.request_handler import RequestHandler
 from a2a.server.request_handlers.response_helpers import (
@@ -12,6 +13,28 @@
 )
 
 
+logger = logging.getLogger(__name__)
+
+try:
+    from a2a.server.request_handlers.grpc_handler import (
+        GrpcHandler,  # type: ignore
+    )
+except ImportError as e:
+    _original_error = e
+    logger.debug(
+        'GrpcHandler not loaded. This is expected if gRPC dependencies are not installed. Error: %s',
+    )
+
+    class GrpcHandler:  # type: ignore
+        """Placeholder for GrpcHandler when dependencies are not installed."""
+
+        def __init__(self, *args, **kwargs):
+            raise ImportError(
+                'To use GrpcHandler, its dependencies must be installed. '
+                'You can install them with \'pip install "a2a-sdk[grpc]"\''
+            ) from _original_error
+
+
 __all__ = [
     'DefaultRequestHandler',
     'GrpcHandler',

src/a2a/server/request_handlers/grpc_handler.py

@@ -5,8 +5,16 @@
 from abc import ABC, abstractmethod
 from collections.abc import AsyncIterable
 
-import grpc
-import grpc.aio
+
+try:
+    import grpc
+    import grpc.aio
+except ImportError as e:
+    raise ImportError(
+        'GrpcHandler requires grpcio and grpcio-tools to be installed. '
+        'Install with: '
+        "'pip install a2a-sdk[grpc]'"
+    ) from e
 
 import a2a.grpc.a2a_pb2_grpc as a2a_grpc
 

src/a2a/utils/proto_utils.py

@@ -28,8 +28,8 @@ def message(cls, message: types.Message | None) -> a2a_pb2.Message | None:
         return a2a_pb2.Message(
             message_id=message.messageId,
             content=[ToProto.part(p) for p in message.parts],
-            context_id=message.contextId,
-            task_id=message.taskId,
+            context_id=message.contextId or '',
+            task_id=message.taskId or '',
             role=cls.role(message.role),
             metadata=ToProto.metadata(message.metadata),
         )
@@ -438,8 +438,8 @@ def message(cls, message: a2a_pb2.Message) -> types.Message:
         return types.Message(
             messageId=message.message_id,
             parts=[FromProto.part(p) for p in message.content],
-            contextId=message.context_id,
-            taskId=message.task_id,
+            contextId=message.context_id or None,
+            taskId=message.task_id or None,
             role=FromProto.role(message.role),
             metadata=FromProto.metadata(message.metadata),
         )