fix: read the data directory before other casings

Widening the name step to every casing served blueMSX a different MSX2P.ROM dump while data/bluemsx held the one it ships.

scripts/common.py

@@ -1365,7 +1365,12 @@ def resolve_local_file(
                     ):
                         candidates.append(path)
         owners = _owner_tokens(file_entry)
-        if not candidates or all(_foreign_tree(p, owners) for p in candidates):
+        # Only another emulator's tree answers the exact casing: what it
+        # holds there says nothing about this entry's file.
+        exact_foreign = bool(candidates) and all(
+            _foreign_tree(p, owners) for p in candidates
+        )
+        if not candidates or exact_foreign:
             # Case-insensitive fallback: upstream platforms disagree on
             # casing (VEC_MineStorm.vec vs VEC_Minestorm.vec). Two casings
             # can name two contents (FONT.ROM and font.rom), so this only
@@ -1403,8 +1408,10 @@ def resolve_local_file(
                 # and a data directory it reads may hold it. Dolphin got
                 # Dolphin-MMJR's codehandler.bin while data/dolphin-sys held
                 # its own; blueMSX got the 16 KB RS232.ROM once msx-emu's
-                # 8 KB copy was set aside, while data/bluemsx held its own.
-                if data_dir_registry and _foreign_tree(best, owners):
+                # 8 KB copy was set aside, while data/bluemsx held its own,
+                # and MSX2P.ROM of another dump once only msx-emu answered
+                # the exact casing.
+                if data_dir_registry and (exact_foreign or _foreign_tree(best, owners)):
                     hit, _mismatch = _resolve_in_data_dirs(
                         names_to_try, data_dir_registry,
                         functools.partial(

tests/test_foreign_tree_names.py

@@ -73,6 +73,26 @@ class ForeignTreeNames(unittest.TestCase):
         self.assertEqual(status, "data_dir")
         self.assertEqual(Path(path).stat().st_size, 64)
 
+    def test_a_casing_only_another_tree_holds_reads_the_data_directory(self):
+        """MSX2P.rom: only msx-emu's tree had the exact casing, and widening
+        to every casing served Microsoft/MSX/MSX2P.ROM, another dump, while
+        data/bluemsx held the one blueMSX ships."""
+        self._hold("bios/Other/msx-emu/Machines/Shared Roms/MSX2P.rom", b"B" * 64)
+        self._hold("bios/Microsoft/MSX/MSX2P.ROM", b"O" * 64)
+        cache = self.root / "data" / "bluemsx"
+        (cache / "Machines" / "Shared Roms").mkdir(parents=True)
+        (cache / "Machines" / "Shared Roms" / "MSX2P.rom").write_bytes(b"B" * 64)
+        entry = {
+            "name": "MSX2P.rom", "path": "Machines/Shared Roms/MSX2P.rom",
+            "source_emulator": "bluemsx",
+        }
+        path, status = resolve_local_file(
+            entry, self.db,
+            data_dir_registry={"bluemsx": {"local_cache": str(cache)}},
+        )
+        self.assertEqual(status, "data_dir")
+        self.assertEqual(Path(path).read_bytes(), b"B" * 64)
+
 
 if __name__ == "__main__":
     unittest.main()