From ced7588d17015a9272df65aedeb32fe0f2fb8b35 Mon Sep 17 00:00:00 2001
From: Abdessamad Derraz <3028866+Abdess@users.noreply.github.com>
Date: Tue, 6 Oct 2026 09:41:53 +0200
Subject: [PATCH] fix: count mister corrections only where it writes

---
 scripts/exporter/misterfpga_exporter.py | 11 ++++++++++-
 tests/test_export_counts.py             | 16 ++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/scripts/exporter/misterfpga_exporter.py b/scripts/exporter/misterfpga_exporter.py
index 208ad091..0c2ad443 100644
--- a/scripts/exporter/misterfpga_exporter.py
+++ b/scripts/exporter/misterfpga_exporter.py
@@ -13,7 +13,7 @@ import zipfile
 from collections import OrderedDict
 
 from .base_exporter import BaseExporter
-from .baseline import NativeSystem, Report
+from .baseline import NativeFile, NativeSystem, Report
 
 SOURCE_URL = (
     "https://raw.githubusercontent.com/ajgowans/BiosDB_MiSTer/db/bios_db.json.zip"
@@ -57,6 +57,13 @@ class Exporter(BaseExporter):
         with zipfile.ZipFile(io.BytesIO(raw)) as archive:
             return {_DB_NAME: archive.read(_DB_NAME).decode("utf-8")}
 
+    def states(self, fe: NativeFile, field_name: str) -> bool:
+        """A correction whose path the database does not hold is not written."""
+        written = getattr(self, "_written", None)
+        if written is not None and id(fe) not in written:
+            return False
+        return super().states(fe, field_name)
+
     def _by_path(self, systems: dict[str, NativeSystem]) -> dict[str, object]:
         indexed: dict[str, object] = {}
         for system in systems.values():
@@ -80,11 +87,13 @@ class Exporter(BaseExporter):
             )
         database = json.loads(original, object_pairs_hook=OrderedDict)
         indexed = self._by_path(systems)
+        self._written = set()
 
         for path, entry in database.get("files", {}).items():
             fe = indexed.get(path)
             if fe is None:
                 continue
+            self._written.add(id(fe))
             md5 = fe.hash("md5")
             if md5:
                 entry["hash"] = md5
diff --git a/tests/test_export_counts.py b/tests/test_export_counts.py
index 41b53924..75f16bbd 100644
--- a/tests/test_export_counts.py
+++ b/tests/test_export_counts.py
@@ -181,6 +181,22 @@ class BizHawkCountsWhatItWrites(unittest.TestCase):
         self.assertFalse(exporter.states(first, "sha1"))
 
 
+class MisterCountsWhatItWrites(unittest.TestCase):
+    def test_a_path_the_database_lacks_is_not_counted(self):
+        from exporter.misterfpga_exporter import Exporter as Mister
+
+        held = NativeFile("boot.rom", "NES/boot.rom", "nes", platform={"md5": A},
+                          truth={"md5": B}, corrections=["md5"])
+        absent = NativeFile("boot.rom", "SNES/boot.rom", "snes", platform={"md5": A},
+                            truth={"md5": C}, corrections=["md5"])
+        systems = {"nes": NativeSystem("nes", files=[held]), "snes": NativeSystem("snes", files=[absent])}
+        database = {"db_id": "x", "files": {"games/NES/boot.rom": {"hash": A, "url": "u"}}}
+        exporter = Mister()
+        exporter.render(systems, None, {"bios_db.json": json.dumps(database)})
+        self.assertTrue(exporter.states(held, "md5"))
+        self.assertFalse(exporter.states(absent, "md5"))
+
+
 class ModelKeepsOneFileOneEntry(unittest.TestCase):
     def test_size_describes_the_hash_written(self):
         fe = NativeFile("boot.bin", "dc/boot.bin", "dc",