refactor: importers write through write_if_changed

game_dat_importer and arcade_parent_importer each kept an exact-text
copy of write_if_changed, so a redump refresh rewrote every catalog for
its fetched date alone. Both now use artifacts.write_if_changed, which
treats fetched as a timestamp. A No-Intro rebuild still rewrites its
catalogs, since asset_updated_at moves with it, so check_freshness keeps
reading a fetched date no older than the pack.

scripts/artifacts.py

@@ -19,6 +19,7 @@ import re
 _TIMESTAMP_PATTERNS = [
     re.compile(r'"generated_at":\s*"[^"]*"'),  # database.json
     re.compile(r'"imported_at":\s*"[^"]*"'),  # provenance snapshots
+    re.compile(r'"fetched":\s*"[^"]*"'),  # games/catalogs/
     re.compile(r"\*Auto-generated on [^*]*\*"),  # README.md
     re.compile(r"\*Generated on [^*]*\*"),  # docs site pages
     # The decorated pages carry the same stamp again as a rendered element,

scripts/scraper/arcade_parent_importer.py

@@ -49,7 +49,7 @@ from collections.abc import Callable, Iterator
 from dataclasses import dataclass, field
 from pathlib import Path
 
-from ..artifacts import write_text_atomic
+from ..artifacts import write_if_changed
 from ..common import load_emulator_profiles, run_cli
 from .romset_dat_importer import (
     LISTXML_CHUNK,
@@ -1114,14 +1114,6 @@ def dump(doc: dict) -> str:
     return json.dumps(doc, sort_keys=True, separators=(",", ":"), ensure_ascii=False) + "\n"
 
 
-def write_if_changed(path: Path, text: str) -> bool:
-    if path.is_file() and path.read_text(encoding="utf-8") == text:
-        return False
-    path.parent.mkdir(parents=True, exist_ok=True)
-    write_text_atomic(str(path), text)
-    return True
-
-
 def main() -> int:
     parser = argparse.ArgumentParser(allow_abbrev=False, description=__doc__.splitlines()[0])
     which = parser.add_mutually_exclusive_group(required=True)
@@ -1197,7 +1189,8 @@ def main() -> int:
             continue
         if not args.dry_run:
             target = args.output_dir / f"{profile}.json"
-            if write_if_changed(target, dump(doc)):
+            target.parent.mkdir(parents=True, exist_ok=True)
+            if write_if_changed(str(target), dump(doc)):
                 print(f"  wrote {target}")
     return 1 if failed else 0
 

scripts/scraper/game_dat_importer.py

@@ -38,7 +38,7 @@ _SCRIPTS_DIR = str(Path(__file__).resolve().parents[1])
 if _SCRIPTS_DIR not in sys.path:
     sys.path.insert(0, _SCRIPTS_DIR)
 
-from artifacts import copy_stream_atomic, write_text_atomic  # noqa: E402
+from artifacts import copy_stream_atomic, write_if_changed, write_text_atomic  # noqa: E402
 from common import parse_untrusted_xml  # noqa: E402
 from region import REGIONS, WORLD  # noqa: E402
 from region_audit import NOINTRO  # noqa: E402
@@ -275,14 +275,6 @@ def dump_catalog(doc: dict) -> str:
     return f'{text},"games":[\n{games}\n]}}\n'
 
 
-def write_if_changed(path: Path, text: str) -> bool:
-    if path.is_file() and path.read_text(encoding="utf-8") == text:
-        return False
-    path.parent.mkdir(parents=True, exist_ok=True)
-    write_text_atomic(str(path), text)
-    return True
-
-
 # Fetching ---------------------------------------------------------------
 
 
@@ -503,7 +495,9 @@ def main() -> int:
             failures.append(f"{doc['source']}/{doc['system']}: {cov['games']} games, "
                             f"floor {floor_of(doc)}")
         if not args.dry_run:
-            write_if_changed(args.output_dir / doc["source"] / f"{doc['system']}.json", text)
+            target = args.output_dir / doc["source"] / f"{doc['system']}.json"
+            target.parent.mkdir(parents=True, exist_ok=True)
+            write_if_changed(str(target), text)
     print(f"{len(docs)} catalogs, {raw_total} bytes raw, {gz_total} bytes gzip")
     for failure in failures:
         print(f"FAIL {failure}", file=sys.stderr)

tests/test_game_catalogs.py

@@ -102,6 +102,17 @@ class FixtureImport(unittest.TestCase):
             twin = second / path.relative_to(first)
             self.assertEqual(path.read_bytes(), twin.read_bytes(), path.name)
 
+    def test_a_new_fetch_date_alone_rewrites_nothing(self) -> None:
+        """A refresh rewrote every catalog for the day it ran, and the diff
+        read before commit no longer showed which DAT had moved."""
+        self.assertEqual(run_import("redump", self.out).returncode, 0)
+        path = self.out / "redump" / "sega-megacd.json"
+        doc = json.loads(path.read_text())
+        doc["fetched"] = "2000-01-01"
+        path.write_text(importer.dump_catalog(doc))
+        self.assertEqual(run_import("redump", self.out).returncode, 0)
+        self.assertEqual(json.loads(path.read_text())["fetched"], "2000-01-01")
+
     def test_floor_refuses_a_short_dat(self) -> None:
         result = run_import("no-intro", self.out, "--floor", "--dry-run")
         self.assertEqual(result.returncode, 1)