Add an option to disable purge in delete room admin API (#7964)

Add option ```purge``` to ```POST /_synapse/admin/v1/rooms/<room_id>/delete```
Fixes: #3761

Signed-off-by: Dirk Klimpel dirk@klimpel.org

4 files changed, 75 insertions, 7 deletions

diff --git a/changelog.d/7964.feature b/changelog.d/7964.feature
new file mode 100644
index 0000000000..ffe861650c
--- /dev/null
+++ b/changelog.d/7964.feature
@@ -0,0 +1 @@
+Add an option to purge room or not with delete room admin endpoint (`POST /_synapse/admin/v1/rooms/<room_id>/delete`). Contributed by @dklimpel.
\ No newline at end of file
diff --git a/docs/admin_api/rooms.md b/docs/admin_api/rooms.md
index 15b83e9824..0f267d2b7b 100644
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -369,7 +369,9 @@ to the new room will have power level `-10` by default, and thus be unable to sp
 If `block` is `True` it prevents new joins to the old room.
 
 This API will remove all trace of the old room from your database after removing
-all local users.
+all local users. If `purge` is `true` (the default), all traces of the old room will
+be removed from your database after removing all local users. If you do not want
+this to happen, set `purge` to `false`.
 Depending on the amount of history being purged a call to the API may take
 several minutes or longer.
 
@@ -388,7 +390,8 @@ with a body of:
     "new_room_user_id": "@someuser:example.com",
     "room_name": "Content Violation Notification",
     "message": "Bad Room has been shutdown due to content violations on this server. Please review our Terms of Service.",
-    "block": true
+    "block": true,
+    "purge": true
 }
 ```
 
@@ -430,8 +433,10 @@ The following JSON body parameters are available:
               `new_room_user_id` in the new room. Ideally this will clearly convey why the
                original room was shut down. Defaults to `Sharing illegal content on this server
                is not permitted and rooms in violation will be blocked.`
-* `block` - Optional. If set to `true`, this room will be added to a blocking list, preventing future attempts to
-  join the room. Defaults to `false`.
+* `block` - Optional. If set to `true`, this room will be added to a blocking list, preventing
+            future attempts to join the room. Defaults to `false`.
+* `purge` - Optional. If set to `true`, it will remove all traces of the room from your database.
+            Defaults to `true`.
 
 The JSON body must not be empty. The body must be at least `{}`.
 
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index b8c95d045a..a8364d9793 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -103,6 +103,14 @@ class DeleteRoomRestServlet(RestServlet):
                 Codes.BAD_JSON,
             )
 
+        purge = content.get("purge", True)
+        if not isinstance(purge, bool):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Param 'purge' must be a boolean, if given",
+                Codes.BAD_JSON,
+            )
+
         ret = await self.room_shutdown_handler.shutdown_room(
             room_id=room_id,
             new_room_user_id=content.get("new_room_user_id"),
@@ -113,7 +121,8 @@ class DeleteRoomRestServlet(RestServlet):
         )
 
         # Purge room
-        await self.pagination_handler.purge_room(room_id)
+        if purge:
+            await self.pagination_handler.purge_room(room_id)
 
         return (200, ret)
 
diff --git a/tests/rest/admin/test_room.py b/tests/rest/admin/test_room.py
index ba8552c29f..cec1cf928f 100644
--- a/tests/rest/admin/test_room.py
+++ b/tests/rest/admin/test_room.py
@@ -283,6 +283,23 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         self.assertEqual(400, int(channel.result["code"]), msg=channel.result["body"])
         self.assertEqual(Codes.BAD_JSON, channel.json_body["errcode"])
 
+    def test_purge_is_not_bool(self):
+        """
+        If parameter `purge` is not boolean, return an error
+        """
+        body = json.dumps({"purge": "NotBool"})
+
+        request, channel = self.make_request(
+            "POST",
+            self.url,
+            content=body.encode(encoding="utf_8"),
+            access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(400, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.BAD_JSON, channel.json_body["errcode"])
+
     def test_purge_room_and_block(self):
         """Test to purge a room and block it.
         Members will not be moved to a new room and will not receive a message.
@@ -297,7 +314,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         # Assert one user in room
         self._is_member(room_id=self.room_id, user_id=self.other_user)
 
-        body = json.dumps({"block": True})
+        body = json.dumps({"block": True, "purge": True})
 
         request, channel = self.make_request(
             "POST",
@@ -331,7 +348,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         # Assert one user in room
         self._is_member(room_id=self.room_id, user_id=self.other_user)
 
-        body = json.dumps({"block": False})
+        body = json.dumps({"block": False, "purge": True})
 
         request, channel = self.make_request(
             "POST",
@@ -351,6 +368,42 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         self._is_blocked(self.room_id, expect=False)
         self._has_no_members(self.room_id)
 
+    def test_block_room_and_not_purge(self):
+        """Test to block a room without purging it.
+        Members will not be moved to a new room and will not receive a message.
+        The room will not be purged.
+        """
+        # Test that room is not purged
+        with self.assertRaises(AssertionError):
+            self._is_purged(self.room_id)
+
+        # Test that room is not blocked
+        self._is_blocked(self.room_id, expect=False)
+
+        # Assert one user in room
+        self._is_member(room_id=self.room_id, user_id=self.other_user)
+
+        body = json.dumps({"block": False, "purge": False})
+
+        request, channel = self.make_request(
+            "POST",
+            self.url.encode("ascii"),
+            content=body.encode(encoding="utf_8"),
+            access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(None, channel.json_body["new_room_id"])
+        self.assertEqual(self.other_user, channel.json_body["kicked_users"][0])
+        self.assertIn("failed_to_kick_users", channel.json_body)
+        self.assertIn("local_aliases", channel.json_body)
+
+        with self.assertRaises(AssertionError):
+            self._is_purged(self.room_id)
+        self._is_blocked(self.room_id, expect=False)
+        self._has_no_members(self.room_id)
+
     def test_shutdown_room_consent(self):
         """Test that we can shutdown rooms with local users who have not
         yet accepted the privacy policy. This used to fail when we tried to