Fixes remove stream tags per list

tests/unit/test_media_descriptor_change_set.py

@@ -0,0 +1,84 @@
+from __future__ import annotations
+
+from pathlib import Path
+import sys
+import unittest
+
+
+SRC_ROOT = Path(__file__).resolve().parents[2] / "src"
+
+if str(SRC_ROOT) not in sys.path:
+    sys.path.insert(0, str(SRC_ROOT))
+
+
+from ffx.media_descriptor import MediaDescriptor  # noqa: E402
+from ffx.media_descriptor_change_set import MediaDescriptorChangeSet  # noqa: E402
+from ffx.track_descriptor import TrackDescriptor  # noqa: E402
+from ffx.track_type import TrackType  # noqa: E402
+from ffx.logging_utils import get_ffx_logger  # noqa: E402
+
+
+class StaticConfig:
+    def __init__(self, data: dict):
+        self._data = data
+
+    def getData(self):
+        return self._data
+
+
+class MediaDescriptorChangeSetTests(unittest.TestCase):
+    def test_external_subtitle_preserves_source_only_tags_except_removed_keys(self):
+        context = {
+            "logger": get_ffx_logger(),
+            "config": StaticConfig(
+                {
+                    "metadata": {
+                        "streams": {
+                            "remove": ["BPS"],
+                        }
+                    }
+                }
+            ),
+        }
+
+        source_track = TrackDescriptor(
+            index=0,
+            source_index=0,
+            sub_index=0,
+            track_type=TrackType.SUBTITLE,
+            tags={
+                "language": "eng",
+                "title": "Embedded Title",
+                "THIS_IS": "embedded-subtitle",
+                "EXTERNAL_KEEP": "keep-me",
+                "BPS": "remove-me",
+            },
+        )
+        target_track = TrackDescriptor(
+            index=0,
+            source_index=0,
+            sub_index=0,
+            track_type=TrackType.SUBTITLE,
+            tags={"language": "deu"},
+            external_source_file="/tmp/external-subtitle.vtt",
+        )
+
+        change_set = MediaDescriptorChangeSet(
+            context,
+            MediaDescriptor(track_descriptors=[target_track]),
+            MediaDescriptor(track_descriptors=[source_track]),
+        )
+
+        metadata_tokens = change_set.generateMetadataTokens()
+
+        self.assertIn("-metadata:s:s:0", metadata_tokens)
+        self.assertIn("language=deu", metadata_tokens)
+        self.assertIn("title=Embedded Title", metadata_tokens)
+        self.assertIn("THIS_IS=embedded-subtitle", metadata_tokens)
+        self.assertIn("EXTERNAL_KEEP=keep-me", metadata_tokens)
+        self.assertNotIn("BPS=remove-me", metadata_tokens)
+        self.assertNotIn("BPS=", metadata_tokens)
+
+
+if __name__ == "__main__":
+    unittest.main()