Recreate user profile on account reactivation (#19902)

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

changelog.d/19902.bugfix

@@ -0,0 +1,2 @@
+Fix a bug introduced in Synapse v1.150.0 where reactivating a deactivated and erased user did not restore their profile, breaking login, name changes, and invitations.
+Contributed by @m4us1ne.

synapse/handlers/deactivate_account.py

@@ -349,6 +349,9 @@ class DeactivateAccountHandler:
         # Ensure the user is not marked as erased.
         await self.store.mark_user_not_erased(user_id)
 
+        # The profile row is deleted on erasure, so recreate it if missing.
+        await self.store.create_profile(user)
+
         # Mark the user as active.
         await self.store.set_user_deactivated_status(user_id, False)
 

synapse/storage/databases/main/profile.py

@@ -293,15 +293,17 @@ class ProfileWorkerStore(SQLBaseStore):
 
     async def create_profile(self, user_id: UserID) -> None:
         """
-        Create a blank profile for a user.
+        Create a blank profile for a user, if one does not already exist.
 
         Args:
             user_id: The user to create the profile for.
         """
         user_localpart = user_id.localpart
-        await self.db_pool.simple_insert(
+        await self.db_pool.simple_upsert(
             table="profiles",
-            values={"user_id": user_localpart, "full_user_id": user_id.to_string()},
+            keyvalues={"full_user_id": user_id.to_string()},
+            values={},
+            insertion_values={"user_id": user_localpart},
             desc="create_profile",
         )
 

tests/handlers/test_deactivate_account.py

@@ -483,3 +483,70 @@ class DeactivateAccountTestCase(HomeserverTestCase):
 
         # Validate that the created room is forgotten
         self.assertTrue(room_id in forgotten_rooms)
+
+    def _get_profile_row(self) -> str | None:
+        """Return the `user_id` of `self.user`'s `profiles` row, or None if absent."""
+        return self.get_success(
+            self._store.db_pool.simple_select_one_onecol(
+                table="profiles",
+                keyvalues={"full_user_id": self.user},
+                retcol="user_id",
+                allow_none=True,
+                desc="_get_profile_row",
+            )
+        )
+
+    def test_reactivation_recreates_profile(self) -> None:
+        """
+        Tests that reactivating an erased user recreates their profile row, so
+        that subsequent profile operations work.
+        """
+        self.assertIsNotNone(self._get_profile_row())
+
+        # Erasure deletes the whole profiles row.
+        self._deactivate_my_account()
+        self.assertIsNone(self._get_profile_row())
+
+        # Reactivating recreates a blank profile row.
+        deactivate_handler = self.hs.get_deactivate_account_handler()
+        self.get_success(deactivate_handler.activate_account(self.user))
+        self.assertIsNotNone(self._get_profile_row())
+
+        # Setting a display name now works again.
+        user = UserID.from_string(self.user)
+        self.get_success(
+            self.hs.get_profile_handler().set_displayname(
+                user, create_requester(user), "Reactivated", by_admin=True
+            )
+        )
+        self.assertEqual(
+            self.get_success(self._store.get_profile_displayname(user)),
+            "Reactivated",
+        )
+
+    def test_reactivation_without_erasure_keeps_profile(self) -> None:
+        """
+        Reactivating a user whose profile row still exists leaves it untouched.
+        """
+        user = UserID.from_string(self.user)
+        self.get_success(
+            self.hs.get_profile_handler().set_displayname(
+                user, create_requester(user), "Original", by_admin=True
+            )
+        )
+
+        # Deactivate without erasure, so the profile row is left intact.
+        deactivate_handler = self.hs.get_deactivate_account_handler()
+        self.get_success(
+            deactivate_handler.deactivate_account(
+                self.user, erase_data=False, requester=create_requester(user)
+            )
+        )
+        self.assertIsNotNone(self._get_profile_row())
+
+        # Reactivating must not raise despite the existing profile row.
+        self.get_success(deactivate_handler.activate_account(self.user))
+        self.assertEqual(
+            self.get_success(self._store.get_profile_displayname(user)),
+            "Original",
+        )