fix: diff every declaration of a repeated destination

scripts/check_freshness.py

@@ -157,6 +157,22 @@ def _core_names(config: dict) -> set[str]:
     return names
 
 
+def _keyed_files(files: list[dict]) -> dict[str, dict]:
+    """Each declaration under its own key.
+
+    A platform declares one destination several times (an archive once per
+    inner ROM, MD5 alternatives): keyed by destination alone, the dict kept
+    the last and a change to the others read as identical.
+    """
+    keyed: dict[str, dict] = {}
+    seen: dict[str, int] = {}
+    for f in files:
+        key = _file_key(f)
+        seen[key] = seen.get(key, 0) + 1
+        keyed[key if seen[key] == 1 else f"{key}#{seen[key]}"] = f
+    return keyed
+
+
 def diff_platform(old: dict, new: dict) -> PlatformDiff:
     """Compare two platform files the way a reviewer reads the diff.
 
@@ -172,12 +188,8 @@ def diff_platform(old: dict, new: dict) -> PlatformDiff:
     diff.systems_added = sorted(set(new_systems) - set(old_systems))
     diff.systems_removed = sorted(set(old_systems) - set(new_systems))
     for system in sorted(set(old_systems) & set(new_systems)):
-        old_files = {
+        old_files = _keyed_files((old_systems[system] or {}).get("files") or [])
-            _file_key(f): f for f in (old_systems[system] or {}).get("files") or []
+        new_files = _keyed_files((new_systems[system] or {}).get("files") or [])
-        }
-        new_files = {
-            _file_key(f): f for f in (new_systems[system] or {}).get("files") or []
-        }
         diff.files_added.extend(
             f"{system}/{k}" for k in sorted(set(new_files) - set(old_files))
         )

tests/test_check_freshness.py

@@ -304,5 +304,19 @@ class RepositoryWiringTests(unittest.TestCase):
         self.assertIn("[data]", text)
 
 
+class RepeatedDestinations(unittest.TestCase):
+    def test_a_change_to_an_earlier_declaration_is_seen(self):
+        from check_freshness import diff_platform  # noqa: PLC0415
+
+        def platform(first_md5: str) -> dict:
+            return {"systems": {"pce": {"files": [
+                {"name": "syscard3.pce", "destination": "syscard3.pce", "md5": first_md5},
+                {"name": "syscard3.pce", "destination": "syscard3.pce", "md5": "b" * 32},
+            ]}}}
+
+        diff = diff_platform(platform("a" * 32), platform("c" * 32))
+        self.assertEqual(diff.files_changed, ["pce/syscard3.pce"])
+
+
 if __name__ == "__main__":
     unittest.main()