Add test and note for handling track without ID3 header

tests/2/test_id3_tagging_with_missing_id3.py

@@ -0,0 +1,48 @@
+import sys
+from pathlib import Path
+import shutil
+import mutagen
+
+TESTS_DIR = Path(__file__).parent.parent
+sys.path.insert(0, str(TESTS_DIR.parent))
+sys.path.insert(0, str(TESTS_DIR.parent / "vistopia"))
+from vistopia.visitor import Visitor
+
+CURR_TEST_DIR = Path(__file__).parent
+
+
+# The missing_id3 file is created using the following command:
+# ffmpeg -f lavfi -i anullsrc=r=44100:cl=mono -t 0.01 -q:a 9 -acodec libmp3lame regular.mp3
+# ffmpeg -i regular.mp3 -map 0:a -codec:a copy -write_id3v1 0 -id3v2_version 0 id3_removed.mp3
+
+
+def test_id3_tagging_with_missing_id3(tmpdir):
+
+    test_mp3 = tmpdir / "id3_removed.mp3"
+
+    shutil.copyfile(
+        CURR_TEST_DIR / "data" / "id3_removed.mp3",
+        test_mp3
+    )
+
+    Visitor.retag(
+        test_mp3,
+        article_info={
+            "title": "测试标题",
+            "sort_number": "7",
+            "content_url": "http://example.com",
+        },
+        series_info={
+            "title": "测试系列",
+            "author": "测试作者",
+        },
+        catalog_info={}
+    )
+
+    from mutagen.easyid3 import EasyID3
+    tag = EasyID3(test_mp3)
+
+    assert tag["title"] == ["测试标题"]
+    assert tag["album"] == ["测试系列"]
+    assert tag["artist"] == ["测试作者"]
+

vistopia/visitor.py

@@ -149,7 +149,7 @@ def save_transcript_with_single_file(self, id: int,
                         print(f"Failed to fetch page using single-file: {e}")
 
     @staticmethod
-    def retag(fname, article_info, catalog_info, series_info):
+    def retag(fname, article_info: dict, catalog_info: dict, series_info: dict):
 
         from mutagen.easyid3 import EasyID3
         from mutagen.id3 import ID3NoHeaderError
@@ -158,6 +158,7 @@ def retag(fname, article_info, catalog_info, series_info):
             track = EasyID3(fname)
         except ID3NoHeaderError:
             # No ID3 tag found, creating a new ID3 tag
+            # See: https://github.com/quodlibet/mutagen/issues/327
             track = EasyID3()
 
         track['title'] = article_info['title']