fix: prefer a data dir to a foreign copy

scripts/common.py

@@ -886,7 +886,28 @@ def resolve_local_file(
             candidates = _by_affinity(candidates, file_entry, dest_hint)
             primary = [p for p in candidates if "/.variants/" not in p]
             if primary or candidates:
-                return (primary[0] if primary else candidates[0]), "name_exact"
+                chosen = primary[0] if primary else candidates[0]
+                # Even the best of them is another emulator's own copy: the
+                # name says nothing about this profile's file, and a data
+                # directory it reads may hold it. Dolphin got Dolphin-MMJR's
+                # codehandler.bin while data/dolphin-sys held its own.
+                if data_dir_registry and _foreign_tree(chosen, _owner_tokens(file_entry)):
+                    hit, _mismatch = _resolve_in_data_dirs(
+                        names_to_try, data_dir_registry,
+                        functools.partial(
+                            declared_hash_verdict,
+                            has_strong_hash=False,
+                            sha1_candidates=set(),
+                            sha256_candidates=set(),
+                            md5_list=[],
+                            crc_candidates=set(),
+                            zipped_file=zipped_file,
+                            declared_size=declared_size,
+                        ),
+                    )
+                    if hit:
+                        return hit
+                return chosen, "name_exact"
 
     # 4. Name + alias fallback with md5_composite + direct MD5 per candidate
     md5_set = set(md5_list)

tests/test_game_data_homonyms.py

@@ -254,6 +254,44 @@ class ReleaseAssetAnswersEveryDeclaredHash(unittest.TestCase):
         self.assertEqual(self._resolve(entry, b"second"), ("big.bin", "release_asset"))
 
 
+class ForeignCopyYieldsToADataDirectory(unittest.TestCase):
+    """codehandler.bin is held by three Dolphin forks under bios/Other/, all
+    different; Dolphin, PrimeHack and Triforce got MMJR's by index order
+    while data/dolphin-sys, which Dolphin reads, held the upstream file."""
+
+    def test_the_data_directory_answers_before_another_emulators_copy(self):
+        import tempfile
+
+        from common import resolve_local_file
+
+        with tempfile.TemporaryDirectory() as tmp:
+            previous = os.getcwd()
+            os.chdir(tmp)
+            self.addCleanup(os.chdir, previous)
+            fork = Path("bios/Other/dolphin-mmjr/codehandler.bin")
+            fork.parent.mkdir(parents=True)
+            fork.write_bytes(b"mmjr")
+            sys_dir = Path("data/dolphin-sys")
+            sys_dir.mkdir(parents=True)
+            (sys_dir / "codehandler.bin").write_bytes(b"upstream")
+            sha = hashlib.sha1(b"mmjr").hexdigest()
+            db = {"files": {sha: {"path": str(fork), "name": "codehandler.bin"}},
+                  "indexes": {"by_name": {"codehandler.bin": [sha]}, "by_md5": {},
+                              "by_crc32": {}, "by_path_suffix": {}}}
+            registry = {"dolphin-sys": {"local_cache": str(sys_dir)}}
+            entry = {"name": "codehandler.bin"}
+            self.assertEqual(
+                resolve_local_file({**entry, "source_profile": "dolphin"}, db,
+                                   data_dir_registry=registry),
+                (str(sys_dir / "codehandler.bin"), "data_dir"),
+            )
+            self.assertEqual(
+                resolve_local_file({**entry, "source_profile": "dolphin-mmjr"}, db,
+                                   data_dir_registry=registry),
+                (str(fork), "name_exact"),
+            )
+
+
 class NameStepPrefersTheOwnersCopy(unittest.TestCase):
     """Same-named files are ordered by where the asking profile keeps its own.