Factor out an `is_mine_server_name` method (#15542)

Add an `is_mine_server_name` method, similar to `is_mine_id`.

Ideally we would use this consistently, instead of sometimes comparing
against `hs.hostname` and other times reaching into
`hs.config.server.server_name`.

Also fix a bug in the tests where `hs.hostname` would sometimes differ
from `hs.config.server.server_name`.

Signed-off-by: Sean Quah <seanq@matrix.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/synapse/rest/media/thumbnail_resource.py b/synapse/rest/media/thumbnail_resource.py
index 4ee2a0dbda..a6396fb05a 100644
--- a/synapse/rest/media/thumbnail_resource.py
+++ b/synapse/rest/media/thumbnail_resource.py
@@ -59,7 +59,7 @@ class ThumbnailResource(DirectServeJsonResource):
         self.media_repo = media_repo
         self.media_storage = media_storage
         self.dynamic_thumbnails = hs.config.media.dynamic_thumbnails
-        self.server_name = hs.hostname
+        self._is_mine_server_name = hs.is_mine_server_name
 
     async def _async_render_GET(self, request: SynapseRequest) -> None:
         set_cors_headers(request)
@@ -71,7 +71,7 @@ class ThumbnailResource(DirectServeJsonResource):
         # TODO Parse the Accept header to get an prioritised list of thumbnail types.
         m_type = "image/png"
 
-        if server_name == self.server_name:
+        if self._is_mine_server_name(server_name):
             if self.dynamic_thumbnails:
                 await self._select_or_generate_local_thumbnail(
                     request, media_id, width, height, method, m_type