[downloader/fragment] Restart inconsistent incomplete fragment downloads (#13731)

[youtube-dl] / youtube_dl / downloader / fragment.py

diff --git a/youtube_dl/downloader/fragment.py b/youtube_dl/downloader/fragment.py
index 50c8254a4f20c840c9bfa6617716823af881b4ac..6f6fb4a77a9dc2b3e4e4278bc51b12755bc709ee 100644 (file)
--- a/youtube_dl/downloader/fragment.py
+++ b/youtube_dl/downloader/fragment.py
@@ -46,9 +46,11 @@ class FragmentFD(FileDownloader):
         Dictionary of downloader related data. May contain following data:
             current_fragment:
                 Dictionary with current (being downloaded) fragment data:
-                index:  Index of current fragment among all fragments
+                index:  0-based index of current fragment among all fragments
             fragment_count:
                 Total count of fragments
+
+    This feature is experimental and file format may change in future.
     """
 
     def report_retry_fragment(self, err, frag_index, count, retries):
@@ -149,12 +151,15 @@ class FragmentFD(FileDownloader):
         if self.__do_ytdl_file(ctx):
             if os.path.isfile(encodeFilename(self.ytdl_filename(ctx['filename']))):
                 self._read_ytdl_file(ctx)
+                if ctx['fragment_index'] > 0 and resume_len == 0:
+                    self.report_error(
+                        'Inconsistent state of incomplete fragment download. '
+                        'Restarting from the beginning...')
+                    ctx['fragment_index'] = resume_len = 0
+                    self._write_ytdl_file(ctx)
             else:
                 self._write_ytdl_file(ctx)
-            if ctx['fragment_index'] > 0:
-                assert resume_len > 0
-            else:
-                assert resume_len == 0
+                assert ctx['fragment_index'] == 0
 
         dest_stream, tmpfilename = sanitize_open(tmpfilename, open_mode)