mkv bug from ffmpeg

src/ytdl_sub/entries/youtube.py

@@ -1,3 +1,5 @@
+import os.path
+from pathlib import Path
 from typing import Optional
 
 from ytdl_sub.entries.entry import Entry
@@ -9,6 +11,18 @@ class YoutubeVideo(YoutubeVideoVariables, Entry):
     Entry object to represent a Youtube video. Reserved for shared Youtube entry logic.
     """
 
+    @property
+    def ext(self) -> str:
+        """
+        With ffmpeg installed, yt-dlp will sometimes merge the file into an mkv file.
+        This is not reflected in the entry. See if the mkv file exists and return "mkv" if so,
+        otherwise, return the original extension.
+        """
+        mkv_file_path = str(Path(self.working_directory()) / f"{self.uid}.mkv")
+        if os.path.isfile(mkv_file_path):
+            return "mkv"
+        return super().ext
+
 
 class YoutubePlaylistVideo(YoutubeVideo):
     @property