fix: Add Input Validation for Task Context IDs in new_task Function

src/a2a/utils/task.py

@@ -18,7 +18,7 @@ def new_task(request: Message) -> Task:
 
     Raises:
         TypeError: If the message role is None.
-        ValueError: If the message parts are empty or if any part has empty content.
+        ValueError: If the message parts are empty, if any part has empty content, or if the provided context_id is invalid.
     """
     if not request.role:
         raise TypeError('Message role cannot be None')
@@ -28,12 +28,25 @@ def new_task(request: Message) -> Task:
         if isinstance(part.root, TextPart) and not part.root.text:
             raise ValueError('TextPart content cannot be empty')
 
+    context_id_str = request.context_id
+    if context_id_str is not None:
+        try:
+            # Validate that the provided context_id is a valid UUID
+            uuid.UUID(context_id_str)
+            context_id = context_id_str
+        except (ValueError, AttributeError, TypeError):
+            # Catch a variety of potential issues with the UUID validation
+            raise ValueError(
+                f"Invalid context_id: '{context_id_str}' is not a valid UUID."
+            )
+    else:
+        # Generate a new UUID if no context_id is provided
+        context_id = str(uuid.uuid4())
+
     return Task(
         status=TaskStatus(state=TaskState.submitted),
         id=(request.task_id if request.task_id else str(uuid.uuid4())),
-        context_id=(
-            request.context_id if request.context_id else str(uuid.uuid4())
-        ),
+        context_id=context_id,
         history=[request],
     )
 

tests/utils/test_task.py

@@ -188,6 +188,45 @@ def test_completed_task_invalid_artifact_type(self):
                 history=[],
             )
 
+    def test_new_task_with_invalid_context_id(self):
+        with pytest.raises(
+            ValueError,
+            match="Invalid context_id: 'not-a-uuid' is not a valid UUID.",
+        ):
+            new_task(
+                Message(
+                    role=Role.user,
+                    parts=[Part(root=TextPart(text='test message'))],
+                    message_id=str(uuid.uuid4()),
+                    context_id='not-a-uuid',
+                )
+            )
+
+    def test_new_task_with_empty_string_context_id(self):
+        with pytest.raises(
+            ValueError, match="Invalid context_id: '' is not a valid UUID."
+        ):
+            new_task(
+                Message(
+                    role=Role.user,
+                    parts=[Part(root=TextPart(text='test message'))],
+                    message_id=str(uuid.uuid4()),
+                    context_id='',
+                )
+            )
+
+    def test_new_task_with_valid_context_id(self):
+        valid_uuid = '123e4567-e89b-12d3-a456-426614174000'
+        task = new_task(
+            Message(
+                role=Role.user,
+                parts=[Part(root=TextPart(text='test message'))],
+                message_id=str(uuid.uuid4()),
+                context_id=valid_uuid,
+            )
+        )
+        self.assertEqual(task.context_id, valid_uuid)
+
 
 if __name__ == '__main__':
     unittest.main()