Import: never wipe a clean/matched import's tags when enhancement fails (#804)

CubeComming #804: since 2.6.7, importing already-tagged files (Bruno Mars,
Coldplay) blanked EVERY tag and filed them under "Unknown Artist". Root cause:
both metadata-enhancement blocks in post_process_matched_download did
`except Exception: wipe_source_tags(file_path)` — a full audio.tags.clear() +
strip + clear_pictures. But enhancement throwing means NO new tags were
written, so wiping just destroys the originals. A transient enhancement error
on a well-tagged file = total metadata loss. (The reported "bitrate change" is
a red herring: mutagen padding on re-save, not a re-encode — ReplayGain only
reads via ffmpeg and tags via mutagen.)

Fix: gate the failure-path wipe on should_wipe_tags_on_enhancement_failure()
(new pure, tested policy) — only wipe UNMATCHED downloads (likely junk source
tags); NEVER wipe a clean/matched import, preserve its existing tags + log.
Unmatched-download behavior is unchanged, so the only thing that changes is the
broken case.

Tests: 3 pin the policy (clean→preserve, unmatched→strip, falsey→strip).
1211 import/pipeline/metadata tests pass.

core/imports/pipeline.py

@@ -62,6 +62,7 @@ from core.runtime_state import (
 )
 from core.metadata.artwork import download_cover_art
 from core.metadata.common import wipe_source_tags
+from core.imports.tag_policy import should_wipe_tags_on_enhancement_failure
 from core.metadata.enrichment import enhance_file_metadata
 from core.imports.paths import (
     build_final_path_for_track,
@@ -590,7 +591,13 @@ def post_process_matched_download(context_key, context, file_path, runtime, meta
             except Exception as meta_err:
                 import traceback
                 pp_logger.info(f"[inner] Metadata enhancement FAILED for {context_key}: {meta_err}\n{traceback.format_exc()}")
-                wipe_source_tags(file_path)
+                if should_wipe_tags_on_enhancement_failure(has_clean_metadata):
+                    wipe_source_tags(file_path)
+                else:
+                    logger.warning(
+                        "[Metadata] Enhancement failed but import has clean/matched metadata — "
+                        "preserving the file's existing tags (not wiping): %s",
+                        os.path.basename(file_path))
 
             logger.info(f"Moving '{os.path.basename(file_path)}' to '{final_path}'")
             safe_move_file(file_path, final_path)
@@ -785,7 +792,13 @@ def post_process_matched_download(context_key, context, file_path, runtime, meta
         except Exception as meta_err:
             import traceback
             pp_logger.info(f"[inner] Metadata enhancement FAILED for {context_key}: {meta_err}\n{traceback.format_exc()}")
-            wipe_source_tags(file_path)
+            if should_wipe_tags_on_enhancement_failure(has_clean_metadata):
+                wipe_source_tags(file_path)
+            else:
+                logger.warning(
+                    "[Metadata] Enhancement failed but import has clean/matched metadata — "
+                    "preserving the file's existing tags (not wiping): %s",
+                    os.path.basename(file_path))
 
         _enhance_source_info = context.get('track_info', {}).get('source_info') or {}
         if isinstance(_enhance_source_info, str):

core/imports/tag_policy.py

@@ -0,0 +1,23 @@
+"""Tag-preservation policy for the import pipeline.
+
+Tiny, pure, and deliberately its own seam: it encodes one rule that, when it
+was wrong, silently destroyed users' metadata (#804). Keeping it here with a
+regression test stops anyone from re-introducing the unconditional wipe.
+"""
+
+from __future__ import annotations
+
+
+def should_wipe_tags_on_enhancement_failure(has_clean_metadata: bool) -> bool:
+    """Whether to strip the file's tags after metadata enhancement raised.
+
+    Enhancement throwing means NO new tags were written, so wiping just
+    destroys whatever the file already had. For a clean/matched import that's
+    catastrophic — #804: already-tagged files (Bruno Mars, Coldplay) got
+    blanked into an "Unknown Artist" folder by a transient enhancement error.
+
+    So: only wipe for UNMATCHED downloads (no clean/matched metadata), where
+    the tags are likely source junk anyway. NEVER wipe a clean/matched import —
+    preserve the user's existing tags.
+    """
+    return not bool(has_clean_metadata)

tests/test_import_tag_preservation.py

@@ -0,0 +1,22 @@
+"""Regression: a metadata-enhancement failure must NOT wipe a clean/matched
+import's tags (#804 — already-tagged files were blanked into Unknown Artist).
+"""
+
+from __future__ import annotations
+
+from core.imports.tag_policy import should_wipe_tags_on_enhancement_failure
+
+
+def test_clean_matched_import_is_never_wiped_on_failure():
+    # The #804 case: matched import (clean metadata) → preserve existing tags.
+    assert should_wipe_tags_on_enhancement_failure(has_clean_metadata=True) is False
+
+
+def test_unmatched_download_still_strips_junk_on_failure():
+    # Unchanged behavior for unmatched downloads (likely junk source tags).
+    assert should_wipe_tags_on_enhancement_failure(has_clean_metadata=False) is True
+
+
+def test_falsey_values_treated_as_unmatched():
+    assert should_wipe_tags_on_enhancement_failure(None) is True
+    assert should_wipe_tags_on_enhancement_failure(0) is True