fix: make the report directory before writing it

A platform with nothing left to correct writes no file, so its output
directory was never made: RetroPie's report then raised
FileNotFoundError into a fresh --output-dir and stopped --all.

scripts/export_native.py

@@ -668,7 +668,10 @@ def write_report(path: Path, report: dict) -> None:
 
     The run prints five examples per kind of change. The page lists them
     all, so the maintainer reading it finds each line of the diff named.
+    A platform with nothing to write made no directory of its own: the
+    output directory itself may not exist yet.
     """
+    path.parent.mkdir(parents=True, exist_ok=True)
     write_if_changed(str(path), json.dumps(report, indent=2) + "\n")
 
 

tests/test_export_report.py

@@ -43,6 +43,14 @@ class ExportReportIsWrittenAndRead(unittest.TestCase):
             (Path(scratch) / "recalbox").mkdir()
             self.assertEqual(load_export_reports(scratch), [report])
 
+    def test_a_report_goes_into_a_directory_not_yet_made(self):
+        """RetroPie with nothing left to correct writes no file, so its
+        output directory was never made and the report crashed --all."""
+        with tempfile.TemporaryDirectory(dir=ROOT / "tmp") as scratch:
+            target = Path(scratch) / "fresh" / "retropie.json"
+            export_native.write_report(target, _report("retropie", []))
+            self.assertTrue(target.exists())
+
     def test_export_keeps_every_change_not_the_printed_five(self):
         source = (ROOT / "scripts" / "export_native.py").read_text(encoding="utf-8")
         body = source[source.index("def export_platform("):source.index("def write_report(")]