Invalidate safe apps for removed chains (#1020)

- Decouples `post_delete` signal from the affected flow, as it remains as it is.
- Change the handling of `post_save` signal to handle `pre_save` signal, to have access to the instance's `Chain` list before the update is made.
- Both the `Chain` items related to the `SafeApp` before and after the update are stored in a `Set` to avoid repetitions. Hooks are dispatched for all the `Chain` items in the set.

src/safe_apps/signals.py

@@ -3,7 +3,13 @@
 
 from django.conf import settings
 from django.core.cache import caches
-from django.db.models.signals import m2m_changed, post_delete, post_save, pre_delete
+from django.db.models.signals import (
+    m2m_changed,
+    post_delete,
+    post_save,
+    pre_delete,
+    pre_save,
+)
 from django.dispatch import receiver
 
 from clients.safe_client_gateway import HookEvent, flush, hook_event
@@ -13,9 +19,26 @@
 logger = logging.getLogger(__name__)
 
 
-@receiver(post_save, sender=SafeApp)
-@receiver(post_delete, sender=SafeApp)
+@receiver(pre_save, sender=SafeApp)
 def on_safe_app_update(sender: SafeApp, instance: SafeApp, **kwargs: Any) -> None:
+    logger.info("Clearing safe-apps cache")
+    caches["safe-apps"].clear()
+    if settings.FF_HOOK_EVENTS:
+        chain_ids = set(instance.chain_ids)
+        if instance.app_id is not None:  # existing SafeApp being updated
+            previous = SafeApp.objects.filter(app_id=instance.app_id).first()
+            if previous is not None:
+                chain_ids.update(previous.chain_ids)
+        for chain_id in chain_ids:
+            hook_event(
+                HookEvent(type=HookEvent.Type.SAFE_APPS_UPDATE, chain_id=chain_id)
+            )
+    else:
+        flush()
+
+
+@receiver(post_delete, sender=SafeApp)
+def on_safe_app_delete(sender: SafeApp, instance: SafeApp, **kwargs: Any) -> None:
     logger.info("Clearing safe-apps cache")
     caches["safe-apps"].clear()
     if settings.FF_HOOK_EVENTS:

src/safe_apps/tests/test_signals_ff_hook_events.py

@@ -78,6 +78,152 @@ def test_on_safe_app_update(self) -> None:
             == "Basic example-token"
         )
 
+    @responses.activate
+    def test_on_safe_app_update_by_adding_chain_ids(self) -> None:
+        responses.add(
+            responses.POST,
+            "http://127.0.0.1/v1/hooks/events",
+            status=200,
+            match=[
+                responses.matchers.header_matcher(
+                    {"Authorization": "Basic example-token"}
+                ),
+                responses.matchers.json_params_matcher(
+                    {"type": "SAFE_APPS_UPDATE", "chainId": "1"}
+                ),
+            ],
+        )
+
+        safe_app = SafeApp(app_id=1, chain_ids=[1])
+        safe_app.save()  # create
+        safe_app.chain_ids = [1, 2, 3]
+        safe_app.save()  # update
+
+        assert len(responses.calls) == 4
+        assert isinstance(responses.calls[0], responses.Call)
+        assert (
+            responses.calls[0].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "1"}'
+        )
+        assert responses.calls[0].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[0].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+        assert isinstance(responses.calls[1], responses.Call)
+        assert (
+            responses.calls[1].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "1"}'
+        )
+        assert responses.calls[1].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[1].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+        assert isinstance(responses.calls[2], responses.Call)
+        assert (
+            responses.calls[2].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "2"}'
+        )
+        assert responses.calls[2].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[2].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+        assert isinstance(responses.calls[3], responses.Call)
+        assert (
+            responses.calls[3].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "3"}'
+        )
+        assert responses.calls[3].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[3].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+
+    @responses.activate
+    def test_on_safe_app_update_by_removing_chain_ids(self) -> None:
+        responses.add(
+            responses.POST,
+            "http://127.0.0.1/v1/hooks/events",
+            status=200,
+            match=[
+                responses.matchers.header_matcher(
+                    {"Authorization": "Basic example-token"}
+                ),
+                responses.matchers.json_params_matcher(
+                    {"type": "SAFE_APPS_UPDATE", "chainId": "1"}
+                ),
+            ],
+        )
+
+        safe_app = SafeApp(app_id=1, chain_ids=[1, 2, 3])
+        safe_app.save()  # create
+        safe_app.chain_ids = [1]
+        safe_app.save()  # update
+
+        assert len(responses.calls) == 6
+        assert isinstance(responses.calls[0], responses.Call)
+        assert (
+            responses.calls[0].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "1"}'
+        )
+        assert responses.calls[0].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[0].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+        assert isinstance(responses.calls[1], responses.Call)
+        assert (
+            responses.calls[1].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "2"}'
+        )
+        assert responses.calls[1].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[1].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+        assert isinstance(responses.calls[2], responses.Call)
+        assert (
+            responses.calls[2].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "3"}'
+        )
+        assert responses.calls[2].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[2].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+        assert isinstance(responses.calls[3], responses.Call)
+        assert (
+            responses.calls[3].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "1"}'
+        )
+        assert responses.calls[3].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[3].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+        assert isinstance(responses.calls[4], responses.Call)
+        assert (
+            responses.calls[4].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "2"}'
+        )
+        assert responses.calls[4].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[4].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+        assert isinstance(responses.calls[5], responses.Call)
+        assert (
+            responses.calls[5].request.body
+            == b'{"type": "SAFE_APPS_UPDATE", "chainId": "3"}'
+        )
+        assert responses.calls[5].request.url == "http://127.0.0.1/v1/hooks/events"
+        assert (
+            responses.calls[5].request.headers.get("Authorization")
+            == "Basic example-token"
+        )
+
     @responses.activate
     def test_on_safe_app_delete(self) -> None:
         responses.add(