fix: the path step checks the size the code reads

The name step refuses a candidate outside the size an entry validates, but the path step returned any hashless file at the tail as path_exact, a proof slots arbitration trusts. A 32 KB cpc6128.rom at ZEsarUX's tail would have been served for its 48 KB composite. No profile hits it today.

scripts/common.py

@@ -1346,7 +1346,12 @@ def resolve_local_file(
                 if not os.path.exists(path):
                     continue
                 if not has_strong_hash:
-                    if not adler32_fits(file_entry, path, db):
+                    # A path names the file, the size the code checks still
+                    # bounds it, as on the name step: ZEsarUX's 48 KB
+                    # cpc6128.rom is not cap32's 32 KB one at the same tail.
+                    if not name_match_size_ok(
+                        file_entry, files_db[match_sha1].get("size")
+                    ) or not adler32_fits(file_entry, path, db):
                         continue
                     return path, "path_exact"
                 status = _record_match_status(match_sha1)

tests/test_path_suffix.py

@@ -251,5 +251,29 @@ class TestForeignTreesAndSharedTails(unittest.TestCase):
         self.assertEqual((status, path), ("path_exact", "bios/Other/emucorex/resources/RedumpDatabase.yaml"))
 
 
+class TestSizeGateOnThePathStep(unittest.TestCase):
+    """The path step took any file at the tail when no hash was declared,
+    while the name step already refused one outside the checked size."""
+
+    def test_a_file_outside_the_checked_size_is_not_path_proof(self):
+        with tempfile.TemporaryDirectory() as root:
+            previous = os.getcwd()
+            os.chdir(root)
+            self.addCleanup(os.chdir, previous)
+            rel = "bios/Other/x/cpc/cpc6128.rom"
+            Path(rel).parent.mkdir(parents=True)
+            Path(rel).write_bytes(b"x" * 32768)
+            sha1 = "e" * 40
+            db = {
+                "files": {sha1: {"path": rel, "name": "cpc6128.rom", "md5": "",
+                                 "size": 32768, "crc32": "", "sha1": sha1}},
+                "indexes": {"by_md5": {}, "by_name": {"cpc6128.rom": [sha1]},
+                            "by_crc32": {}, "by_path_suffix": {"cpc/cpc6128.rom": [sha1]}},
+            }
+            entry = {"name": "cpc6128.rom", "size": 49152, "validation": ["size"]}
+            _path, status = resolve_local_file(entry, db, dest_hint="cpc/cpc6128.rom")
+        self.assertNotEqual(status, "path_exact")
+
+
 if __name__ == "__main__":
     unittest.main()