fix: hand RetroDECK manifests back as written

With nothing to correct, nine of ten manifests still changed: a final
newline was added where the original ends without one, "md5": null was
written 39 times where no md5 key was, and PPSSPP's single bios object
became a list rebuilt from our data. A manifest now ends as the
original does, keeps no key it did not have, and a single object stays
one while nothing is added. An empty truth gives back every cached
manifest byte for byte.

scripts/exporter/retrodeck_exporter.py

@@ -222,6 +222,9 @@ class Exporter(BaseExporter):
 
         merged: list[OrderedDict] = []
         corrected: set[tuple[str, str]] = set()
+        # PPSSPP writes its one BIOS as an object, not a list of one.
+        if isinstance(existing, dict):
+            existing = [existing]
         entries = [e for e in existing if isinstance(e, dict)] if isinstance(existing, list) else []
         # A name and system declared several times are several revisions (the
         # 64DD IPL USA and Dev): one entry of ours corrects the revision it
@@ -260,7 +263,12 @@ class Exporter(BaseExporter):
                 if field in cls.carries() and field not in by_key[keys[0]]:
                     combined.pop(field, None)
             if _md5_set(entry.get("md5")) == _md5_set(combined.get("md5")):
-                combined["md5"] = entry.get("md5")
+                # Their own spelling, and no key where they wrote none: an
+                # equal empty set wrote "md5": null 39 times.
+                if "md5" in entry:
+                    combined["md5"] = entry["md5"]
+                else:
+                    combined.pop("md5", None)
             elif isinstance(entry.get("md5"), list) and isinstance(combined.get("md5"), str):
                 combined["md5"] = [combined["md5"]]
             merged.append(combined)
@@ -322,8 +330,11 @@ class Exporter(BaseExporter):
                     )
                 else:
                     container, key = holder
-                    container[key] = self._merge(
-                        container.get(key), entries, additions, appended
+                    written = container.get(key)
+                    merged = self._merge(written, entries, additions, appended)
+                    # A single object stays one while nothing is added to it.
+                    container[key] = (
+                        merged[0] if isinstance(written, dict) and len(merged) == 1 else merged
                     )
                 break
             # A declared entry whose revision the platform does not hold is
@@ -334,7 +345,10 @@ class Exporter(BaseExporter):
                 and (str(fe.name), str(fe.native_system)) in appended
             )
 
-            produced[path] = json.dumps(manifest, indent=2, ensure_ascii=False) + "\n"
+            # Nine of ten manifests end without a newline: the file ends as
+            # theirs does.
+            ending = "\n" if original.endswith("\n") else ""
+            produced[path] = json.dumps(manifest, indent=2, ensure_ascii=False) + ending
 
         return produced
 
@@ -366,7 +380,8 @@ class Exporter(BaseExporter):
                 if holder is None:
                     continue
                 container, key = holder
-                for entry in container[key]:
+                listed = container[key]
+                for entry in [listed] if isinstance(listed, dict) else listed:
                     declared.add(entry.get("filename", ""))
                     placed.add((entry.get("filename", ""), _paths_key(entry)))
                 if not component_value.get("name") and not component_value.get(

tests/test_exporters.py

@@ -1420,6 +1420,42 @@ class BizhawkExport(unittest.TestCase):
         self.assertFalse(exporter.states(entry, "sha1"))
 
 
+class RetrodeckManifestsComeBackAsWritten(unittest.TestCase):
+    """With nothing to correct, a manifest is the platform's own bytes. The
+    export added a final newline to nine of ten, wrote "md5": null where no
+    md5 key was, and turned PPSSPP's single bios object into a list."""
+
+    def test_an_empty_truth_hands_back_every_manifest(self):
+        cache = UPSTREAM_CACHE / "retrodeck"
+        manifests = sorted(cache.glob("*/component_manifest.json"))
+        if not manifests:
+            self.skipTest("upstream cache not populated")
+        exporter = discover_exporters()["retrodeck"]()
+        config = native_layer(load_platform_config("retrodeck", str(REPO_ROOT / "platforms")))
+        systems, report = build_native_model({"systems": {}}, config)
+        originals = {f"{m.parent.name}/component_manifest.json": m.read_text(encoding="utf-8")
+                     for m in manifests}
+        produced = exporter.render(systems, report, originals, config)
+        for path, text in produced.items():
+            with self.subTest(manifest=path):
+                self.assertEqual(text, originals[path])
+
+    def test_no_md5_key_is_made_up(self):
+        from exporter.retrodeck_exporter import Exporter  # noqa: PLC0415
+
+        mine = OrderedDict([("filename", "bios.bin"), ("system", "xbox"), ("required", "Yes")])
+        (merged,) = Exporter._merge([OrderedDict(mine)], [OrderedDict(mine)])
+        self.assertNotIn("md5", merged)
+
+    def test_a_single_bios_object_stays_an_object(self):
+        from exporter.retrodeck_exporter import Exporter  # noqa: PLC0415
+
+        theirs = OrderedDict([("filename", "ppge_atlas.zim"), ("system", "psp"),
+                              ("md5", "a" * 32)])
+        merged = Exporter._merge(OrderedDict(theirs), [])
+        self.assertEqual(merged, [theirs])
+
+
 class RetrodeckExport(unittest.TestCase):
     A, B, C = "a" * 32, "b" * 32, "c" * 32