fix(api): a VM action answers with what the page would have shown after it

The API's VM actions call the web views and only looked at the status
code; the views report a partial result (a disk that was not deleted or
was kept, a template that was not started) as a message for the page
they redirect to. The API reported plain success and left the messages in
the session. Its answer now carries them in "messages".

instances/api/viewsets.py

@@ -1,6 +1,7 @@
 from admin.permissions import IsSuperUser
 from computes import utils
 from computes.models import Compute
+from django.contrib.messages import get_messages
 from django.http import Http404
 from django.shortcuts import get_object_or_404
 from django.urls import reverse
@@ -23,7 +24,7 @@ from operations.api.serializers import OperationSerializer
 from rest_framework import permissions, status, viewsets
 from rest_framework.decorators import action
 from rest_framework.response import Response
-from webvirtcloud.serializers import StatusSerializer
+from webvirtcloud.serializers import ActionStatusSerializer
 
 from .serializers import (
     CreateInstanceSerializer,
@@ -39,7 +40,9 @@ def instance_action_response(action, request, pk, message):
     response = action(request, pk)
     if response.status_code >= 400:
         return response
-    return Response({"status": message})
+    # the page's view reports a partial result (a disk that was kept) as a
+    # message for the page it redirects to: the API answers with them
+    return Response({"status": message, "messages": [str(m) for m in get_messages(request)]})
 
 
 class InstancesViewSet(viewsets.ViewSet):
@@ -121,14 +124,14 @@ class InstanceViewSet(viewsets.ViewSet):
 
         return Response(serializer.data)
 
-    @extend_schema(request=DestroyOptionsSerializer, responses=StatusSerializer)
+    @extend_schema(request=DestroyOptionsSerializer, responses=ActionStatusSerializer)
     def destroy(self, request, pk=None, compute_pk=None):
         queryset = get_instance(request.user, pk, perm_type="delete")
         if compute_pk is not None and str(queryset.compute_id) != str(compute_pk):
             raise Http404()
         return instance_action_response(instance_destroy, request, pk, "Instance is destroyed")
 
-    @extend_schema(request=None, responses=StatusSerializer)
+    @extend_schema(request=None, responses=ActionStatusSerializer)
     @action(detail=True, methods=["post"])
     def poweron(self, request, pk=None, compute_pk=None):
         queryset = get_instance(request.user, pk, perm_type="power")
@@ -138,7 +141,7 @@ class InstanceViewSet(viewsets.ViewSet):
             return Response({"status": "Templates cannot be started"}, status=status.HTTP_409_CONFLICT)
         return instance_action_response(poweron, request, pk, "poweron command send")
 
-    @extend_schema(request=None, responses=StatusSerializer)
+    @extend_schema(request=None, responses=ActionStatusSerializer)
     @action(detail=True, methods=["post"])
     def poweroff(self, request, pk=None, compute_pk=None):
         queryset = get_instance(request.user, pk, perm_type="power")
@@ -146,7 +149,7 @@ class InstanceViewSet(viewsets.ViewSet):
             raise Http404()
         return instance_action_response(poweroff, request, pk, "poweroff command send")
 
-    @extend_schema(request=None, responses=StatusSerializer)
+    @extend_schema(request=None, responses=ActionStatusSerializer)
     @action(detail=True, methods=["post"])
     def powercycle(self, request, pk=None, compute_pk=None):
         queryset = get_instance(request.user, pk, perm_type="power")
@@ -156,7 +159,7 @@ class InstanceViewSet(viewsets.ViewSet):
             return Response({"status": "Templates cannot be started"}, status=status.HTTP_409_CONFLICT)
         return instance_action_response(powercycle, request, pk, "powercycle command send")
 
-    @extend_schema(request=None, responses=StatusSerializer)
+    @extend_schema(request=None, responses=ActionStatusSerializer)
     @action(detail=True, methods=["post"])
     def forceoff(self, request, pk=None, compute_pk=None):
         queryset = get_instance(request.user, pk, perm_type="power")
@@ -164,7 +167,7 @@ class InstanceViewSet(viewsets.ViewSet):
             raise Http404()
         return instance_action_response(force_off, request, pk, "force off command send")
 
-    @extend_schema(request=None, responses=StatusSerializer)
+    @extend_schema(request=None, responses=ActionStatusSerializer)
     @action(detail=True, methods=["post"])
     def suspend(self, request, pk=None, compute_pk=None):
         queryset = get_instance(request.user, pk)
@@ -172,7 +175,7 @@ class InstanceViewSet(viewsets.ViewSet):
             raise Http404()
         return instance_action_response(suspend, request, pk, "suspend command send")
 
-    @extend_schema(request=None, responses=StatusSerializer)
+    @extend_schema(request=None, responses=ActionStatusSerializer)
     @action(detail=True, methods=["post"])
     def resume(self, request, pk=None, compute_pk=None):
         queryset = get_instance(request.user, pk)

instances/tests/test_destroy.py

@@ -65,6 +65,20 @@ class DestroyOrderTestCase(TestCase):
                 self.assertEqual(response.status_code, 200)
                 self.assertEqual(proxy.get_volume_by_path.called, deleted)
 
+    def test_the_api_tells_which_disks_were_not_deleted(self):
+        with patch("instances.models.wvmInstance") as wvm:
+            proxy = wvm.return_value
+            proxy.instance.isActive.return_value = False
+            proxy.split_disk_paths_by_use.return_value = (["/pool/own.qcow2"], ["/pool/shared.qcow2"])
+            proxy.backing_path.return_value = None
+            proxy.get_volume_by_path.return_value.delete.side_effect = libvirtError("Permission denied")
+            url = f"/api/v1/computes/{self.instance.compute_id}/instances/{self.instance.id}/"
+            response = self.client.delete(url, {"delete_disk": True}, content_type="application/json")
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.json(), {"status": "Instance is destroyed", "messages": [
+            "The VM is removed, but disk /pool/own.qcow2 was not deleted: Permission denied",
+            "Disk /pool/shared.qcow2 is used by another VM and was kept"]})
+
     def test_a_disk_file_that_stays_keeps_the_files_it_needs(self):
         # the overlay is not deleted: the file below it would leave it broken
         volumes = {}

webvirtcloud/serializers.py

@@ -5,3 +5,10 @@ class StatusSerializer(serializers.Serializer):
     """Response body of API actions that only report a status message."""
 
     status = serializers.CharField()
+
+
+class ActionStatusSerializer(StatusSerializer):
+    """A VM action's status and what the web page would have shown after it,
+    such as a disk that was kept or a template that was not started."""
+
+    messages = serializers.ListField(child=serializers.CharField())