fix: keep platform hashes cores disagree on

When two cores declare different values for one file, the truth keeps the first and marks the entry hash_conflict. Its hashes pair an entry and never replace the platform's: armsx2's GameIndex.yaml no longer overwrites System.dat's line for LRPS2.

scripts/exporter/baseline.py

@@ -45,8 +45,17 @@ def checked_hashes(entry: dict | None) -> dict | None:
     MT32_CONTROL.ROM against nine sha1, and the one md5 beside them
     replaced System.dat's, another accepted revision. Such a value still
     pairs a renamed file, it never corrects or fills one.
+
+    `hash_conflict` marks an entry whose cores declare different values: the
+    truth kept the first core's, so its hashes describe one revision among
+    those the cores accept. armsx2 and yaps2 disagree on GameIndex.yaml, and
+    armsx2's revision replaced System.dat's line for LRPS2.
     """
-    if not entry or entry.get("validation") is None:
+    if not entry:
+        return entry
+    if entry.get("hash_conflict"):
+        return {k: v for k, v in entry.items() if k not in HASH_FIELDS}
+    if entry.get("validation") is None:
         return entry
     raw = entry["validation"]
     if isinstance(raw, dict):

scripts/truth.py

@@ -316,6 +316,9 @@ def _merge_hashes(
                 existing[h] = [*o_list, *added]
             continue
         if not {str(v).lower() for v in t_list} & {str(v).lower() for v in o_list}:
+            # The value kept is one revision among those the cores accept:
+            # it pairs an entry, it never overrules one (checked_hashes).
+            existing["hash_conflict"] = sorted({*existing.get("hash_conflict", ()), h})
             # Once per process: a run over every platform met the same pair
             # once per platform and opened its output on six copies.
             key = (file_entry["name"], h, str(ours), str(theirs), emu_name)

tests/test_exporters.py

@@ -324,6 +324,30 @@ class Reconciliation(unittest.TestCase):
         self.assertEqual(systems["coco"].files[0].hash("md5"), "a" * 32)
         self.assertEqual(report.hashes_corrected, ["coco/bas12.rom md5"])
 
+    def test_a_hash_the_cores_disagree_on_corrects_nothing(self):
+        """armsx2 and yaps2 declare different revisions of GameIndex.yaml.
+        The truth kept armsx2's, and the export wrote it over System.dat's
+        line for LRPS2 as a hash and size correction."""
+        import contextlib  # noqa: PLC0415
+
+        import truth as truth_module  # noqa: PLC0415
+
+        entry = {"name": "GameIndex.yaml", "sha1": "1" * 40, "size": 2690355}
+        with contextlib.redirect_stderr(io.StringIO()):
+            truth_module._merge_hashes(
+                entry, {"name": "GameIndex.yaml", "sha1": "2" * 40}, "yaps2"
+            )
+        self.assertEqual(entry["hash_conflict"], ["sha1"])
+        truth = {"systems": {"sony-playstation-2": {"files": [entry]}}}
+        scraped = {"systems": {"sony-playstation-2": {"native_id": "ps2", "files": [
+            {"name": "GameIndex.yaml", "destination": "pcsx2/resources/GameIndex.yaml",
+             "native_system": "ps2", "sha1": "3" * 40, "size": 1737799},
+        ]}}}
+        systems, report = build_native_model(truth, scraped)
+        line = systems["ps2"].files[0]
+        self.assertEqual((line.hash("sha1"), line.size()), ("3" * 40, 1737799))
+        self.assertEqual(report.hashes_corrected, [])
+
     def test_the_diff_names_no_mismatch_the_code_does_not_check(self):
         from truth import _diff_system
         truth_sys = {"files": [{"name": "scph1001.bin", "md5": "a" * 32,