REST: Null out previous, current relation info

These fields don't work like we expect them to. Because we're linking to
a non-idempotent entity, an instance of 'relation', what we're storing
in either of these fields is subject to change as patches are added and
removed. This makes the information pretty much useless after the fact.
It's best to just state the patch and request that people query the
information themselves if necessary. We don't want to remove the field
entirely from the API - that would be a truly breaking change - so
instead we null it out like we do for patch tags. In a v2 API (i.e. a
major version bump) we can remove this entirely.

A small bug with the schema generation is corrected.

Signed-off-by: Stephen Finucane <stephen@that.guru>
Related: #379

6 files changed, 28 insertions, 38 deletions

diff --git a/docs/api/schemas/patchwork.j2 b/docs/api/schemas/patchwork.j2
index c55f6f4..af20743 100644
--- a/docs/api/schemas/patchwork.j2
+++ b/docs/api/schemas/patchwork.j2
@@ -1765,7 +1765,7 @@ components:
                 current_state:
                   title: Current state
                   type: string
-{% if version >= (1, 1) %}
+{% if version >= (1, 2) %}
     EventPatchRelationChanged:
       allOf:
         - $ref: '#/components/schemas/EventBase'
@@ -1781,9 +1781,11 @@ components:
                 previous_relation:
                   title: Previous relation
                   type: string
+                  nullable: true
                 current_relation:
                   title: Current relation
                   type: string
+                  nullable: true
 {% endif %}
     EventPatchDelegated:
       allOf:
diff --git a/docs/api/schemas/v1.1/patchwork.yaml b/docs/api/schemas/v1.1/patchwork.yaml
index 5acd33a..3b75c54 100644
--- a/docs/api/schemas/v1.1/patchwork.yaml
+++ b/docs/api/schemas/v1.1/patchwork.yaml
@@ -1510,24 +1510,6 @@ components:
                 current_state:
                   title: Current state
                   type: string
-    EventPatchRelationChanged:
-      allOf:
-        - $ref: '#/components/schemas/EventBase'
-        - type: object
-          properties:
-            category:
-              enum:
-                - patch-relation-changed
-            payload:
-              properties:
-                patch:
-                  $ref: '#/components/schemas/PatchEmbedded'
-                previous_relation:
-                  title: Previous relation
-                  type: string
-                current_relation:
-                  title: Current relation
-                  type: string
     EventPatchDelegated:
       allOf:
         - $ref: '#/components/schemas/EventBase'
diff --git a/docs/api/schemas/v1.2/patchwork.yaml b/docs/api/schemas/v1.2/patchwork.yaml
index 712d137..17d948a 100644
--- a/docs/api/schemas/v1.2/patchwork.yaml
+++ b/docs/api/schemas/v1.2/patchwork.yaml
@@ -1712,9 +1712,11 @@ components:
                 previous_relation:
                   title: Previous relation
                   type: string
+                  nullable: true
                 current_relation:
                   title: Current relation
                   type: string
+                  nullable: true
     EventPatchDelegated:
       allOf:
         - $ref: '#/components/schemas/EventBase'
diff --git a/patchwork/api/event.py b/patchwork/api/event.py
index 75bf870..71f9593 100644
--- a/patchwork/api/event.py
+++ b/patchwork/api/event.py
@@ -33,10 +33,8 @@ class EventSerializer(ModelSerializer):
     current_delegate = UserSerializer()
     created_check = SerializerMethodField()
     created_check = CheckSerializer()
-    previous_relation = PatchSerializer(
-        source='previous_relation.patches', many=True, default=None)
-    current_relation = PatchSerializer(
-        source='current_relation.patches', many=True, default=None)
+    previous_relation = SerializerMethodField()
+    current_relation = SerializerMethodField()
 
     _category_map = {
         Event.CATEGORY_COVER_CREATED: ['cover'],
@@ -53,6 +51,12 @@ class EventSerializer(ModelSerializer):
         Event.CATEGORY_SERIES_COMPLETED: ['series'],
     }
 
+    def get_previous_relation(self, instance):
+        return None
+
+    def get_current_relation(self, instance):
+        return None
+
     def to_representation(self, instance):
         data = super(EventSerializer, self).to_representation(instance)
         payload = OrderedDict()
@@ -72,10 +76,12 @@ class EventSerializer(ModelSerializer):
 
     class Meta:
         model = Event
-        fields = ('id', 'category', 'project', 'date', 'actor', 'patch',
-                  'series', 'cover', 'previous_state', 'current_state',
-                  'previous_delegate', 'current_delegate', 'created_check',
-                  'previous_relation', 'current_relation',)
+        fields = (
+            'id', 'category', 'project', 'date', 'actor', 'patch',
+            'series', 'cover', 'previous_state', 'current_state',
+            'previous_delegate', 'current_delegate', 'created_check',
+            'previous_relation', 'current_relation',
+        )
         read_only_fields = fields
         versioned_fields = {
             '1.2': ('actor', ),
diff --git a/patchwork/signals.py b/patchwork/signals.py
index 4db9909..dc08129 100644
--- a/patchwork/signals.py
+++ b/patchwork/signals.py
@@ -137,14 +137,12 @@ def create_patch_delegated_event(sender, instance, raw, **kwargs):
 @receiver(pre_save, sender=Patch)
 def create_patch_relation_changed_event(sender, instance, raw, **kwargs):
 
-    def create_event(patch, before, after):
+    def create_event(patch):
         return Event.objects.create(
             category=Event.CATEGORY_PATCH_RELATION_CHANGED,
             project=patch.project,
             actor=getattr(patch, '_edited_by', None),
-            patch=patch,
-            previous_relation=before,
-            current_relation=after)
+            patch=patch)
 
     # don't trigger for items loaded from fixtures or new items
     if raw or not instance.pk:
@@ -155,7 +153,7 @@ def create_patch_relation_changed_event(sender, instance, raw, **kwargs):
     if orig_patch.related == instance.related:
         return
 
-    create_event(instance, orig_patch.related, instance.related)
+    create_event(instance)
 
 
 @receiver(pre_save, sender=Patch)
diff --git a/patchwork/tests/test_events.py b/patchwork/tests/test_events.py
index 5bac778..090b6dc 100644
--- a/patchwork/tests/test_events.py
+++ b/patchwork/tests/test_events.py
@@ -190,8 +190,8 @@ class PatchChangedTest(_BaseTestCase):
         self.assertEqual(
             events[1].category, Event.CATEGORY_PATCH_RELATION_CHANGED)
         self.assertEqual(events[1].project, patches[1].project)
-        self.assertEqual(events[1].previous_relation, None)
-        self.assertEqual(events[1].current_relation, relation)
+        self.assertIsNone(events[1].previous_relation)
+        self.assertIsNone(events[1].current_relation)
 
         # add the third patch
 
@@ -203,8 +203,8 @@ class PatchChangedTest(_BaseTestCase):
         self.assertEqual(
             events[1].category, Event.CATEGORY_PATCH_RELATION_CHANGED)
         self.assertEqual(events[1].project, patches[1].project)
-        self.assertEqual(events[1].previous_relation, None)
-        self.assertEqual(events[1].current_relation, relation)
+        self.assertIsNone(events[1].previous_relation)
+        self.assertIsNone(events[1].current_relation)
 
         # drop the third patch
 
@@ -216,8 +216,8 @@ class PatchChangedTest(_BaseTestCase):
         self.assertEqual(
             events[2].category, Event.CATEGORY_PATCH_RELATION_CHANGED)
         self.assertEqual(events[2].project, patches[1].project)
-        self.assertEqual(events[2].previous_relation, relation)
-        self.assertEqual(events[2].current_relation, None)
+        self.assertIsNone(events[2].previous_relation)
+        self.assertIsNone(events[2].current_relation)
 
 
 class CheckCreatedTest(_BaseTestCase):