Fix local-priority merge to avoid remote reorders in conflicts

app/utils/playlist_merge.py

@@ -76,6 +76,7 @@ class MergeChunk:
     base_text: str | None = None
     local_text: str | None = None
     remote_text: str | None = None
+    origin: str | None = None
 
 
 @dataclass
@@ -126,15 +127,25 @@ def _normalize_inputs(
 def _merge_chunks(
     base_paths: Sequence[str], local_paths: Sequence[str], remote_paths: Sequence[str]
 ) -> list[MergeChunk]:
-    """Run a diff3 merge on normalized playlists and return merge chunks."""
-
     merger = Merge3(base_paths, local_paths, remote_paths)
+    raw_chunks = list(merger.merge_groups())
     chunks: list[MergeChunk] = []
 
-    for group in merger.merge_groups():
-        kind = group[0]
+    for kind, *payload in raw_chunks:
         if kind == "conflict":
-            base_lines, local_lines, remote_lines = group[1], group[2], group[3]
+            base_lines, local_lines, remote_lines = payload  # type: ignore[misc]
+
+            # Absorb trailing side-only chunks that actually belong to this
+            # conflicting region (common in reorder scenarios).
+            while chunks and chunks[-1].origin in ("a", "b"):
+                previous = chunks.pop()
+                previous_lines = previous.text.splitlines() if previous.text else []
+
+                if previous.origin == "a":
+                    local_lines = previous_lines + local_lines
+                else:
+                    remote_lines = previous_lines + remote_lines
+
             chunks.append(
                 MergeChunk(
                     type="conflict",
@@ -144,16 +155,11 @@ def _merge_chunks(
                 )
             )
         else:
-            if kind in ("unchanged", "same", "a", "b"):
-                lines = group[1]
-                chunks.append(
-                    MergeChunk(
-                        type="normal",
-                        text=playlist_to_text(lines),
-                    )
-                )
-            else:
-                raise ValueError(f"Unsupported merge chunk type: {kind}")
+            lines = payload[0]
+            if not lines:
+                continue
+            chunk = MergeChunk(type="normal", text=playlist_to_text(lines), origin=kind)
+            chunks.append(chunk)
 
     return chunks
 
@@ -213,12 +219,19 @@ def merge_playlists(
     )
 
     chunks = _merge_chunks(base_paths, local_paths, remote_paths)
+    has_conflict = any(chunk.type == "conflict" for chunk in chunks)
 
     merged_lines: list[str] = []
     conflicts: list[dict] = []
 
     for chunk in chunks:
         if chunk.type == "normal":
+            if (
+                strategy == ConflictResolutionStrategy.LOCAL_PRIORITY
+                and has_conflict
+                and chunk.origin == "b"
+            ):
+                continue
             merged_lines.extend(chunk.text.splitlines())
         else:
             conflict_info = {