check if app spec is updated on re-deploy (#642)

This PR changes the behavior of re-deploying an app where no changes
have been made. Instead of erroring out, it will pass through
gracefully.

Signed-off-by: Niels Bantilan <niels.bantilan@gmail.com>

Author: cosmicBboy

src/flyte/remote/_app.py

@@ -3,6 +3,7 @@
 from contextlib import asynccontextmanager, contextmanager
 from typing import AsyncGenerator, AsyncIterator, Generator, Literal, Mapping, Tuple, cast
 
+import google.protobuf.json_format
 import grpc
 import rich.repr
 from flyteidl2.app import app_definition_pb2, app_payload_pb2
@@ -268,6 +269,23 @@ async def delete(
                 return
             raise
 
+    @staticmethod
+    async def _app_specs_are_equal(
+        old_app_spec: app_definition_pb2.Spec, updated_app_spec: app_definition_pb2.Spec
+    ) -> bool:
+        """
+        Compare two app specs and return True if they are the same.
+
+        If the updated_app_spec doesn't have any ingress defined, use the old app spec's ingress.
+        """
+        old_app_spec_json = google.protobuf.json_format.MessageToDict(old_app_spec)
+        updated_app_spec_json = google.protobuf.json_format.MessageToDict(updated_app_spec)
+        old_ingress = old_app_spec_json.get("ingress")
+        assert old_ingress is not None
+        if not updated_app_spec_json.get("ingress"):
+            updated_app_spec_json["ingress"] = old_ingress
+        return old_app_spec_json == updated_app_spec_json
+
     @syncify
     @classmethod
     async def replace(
@@ -290,7 +308,13 @@ async def replace(
         """
         ensure_client()
         app = await cls.get.aio(name=name, project=project, domain=domain)
+
         updated_app_spec.creator.CopyFrom(app.pb2.spec.creator)
+
+        if await cls._app_specs_are_equal(app.pb2.spec, updated_app_spec):
+            logger.warning(f"No changes in the App spec for '{name}', skipping update")
+            return app
+
         new_app = app_definition_pb2.App(
             metadata=app_definition_pb2.Meta(
                 id=app.pb2.metadata.id,