fix: export only what the platform declares

tests/test_export_native_layer.py

@@ -0,0 +1,68 @@
+"""An export starts from the platform's own file, not from what we add to it.
+
+load_platform_config folds _shared.yml groups into a platform for the pack,
+the RomM scraper repeats tg16's firmware under turbografx-cd, and the
+libretro scraper adds files it traced in the cores' source. None of them is
+in the platform's file. The export counted them kept and wrote them into
+libretro's System.dat (N88EXT0-3.ROM) as if libretro declared them.
+"""
+
+from __future__ import annotations
+
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+sys.path.insert(0, str(REPO_ROOT / "scripts"))
+
+import common  # noqa: E402
+from export_native import load_inputs  # noqa: E402
+
+
+class TheNativeLayerIsThePlatformsOwn(unittest.TestCase):
+    def setUp(self):
+        common._platform_config_cache.clear()
+        common._shared_yml_cache.clear()
+        self.addCleanup(common._platform_config_cache.clear)
+        self.addCleanup(common._shared_yml_cache.clear)
+
+    def test_shared_and_mirrored_entries_are_left_out(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            platforms = Path(tmp)
+            (platforms / "_shared.yml").write_text(
+                "shared_groups:\n  quasi88:\n"
+                "    - name: N88EXT0.ROM\n      destination: quasi88/N88EXT0.ROM\n"
+            )
+            (platforms / "demo.yml").write_text(
+                "platform: Demo\nsystems:\n"
+                "  nec-pc-88:\n    includes: [quasi88]\n    files:\n"
+                "      - name: n88.rom\n        destination: quasi88/n88.rom\n"
+                "  tg16:\n    files:\n"
+                "      - name: syscard3.pce\n        destination: tg16/syscard3.pce\n"
+                "      - name: syscard3.pce\n        destination: turbografx-cd/syscard3.pce\n"
+                "        mirror_of: tg16\n"
+                "  nintendo-gamecube:\n    files:\n"
+                "      - name: dsp_rom.bin\n        destination: dolphin-emu/Sys/GC/dsp_rom.bin\n"
+                "        curated: true\n"
+            )
+            pack_view = common.load_platform_config("demo", str(platforms))
+            _truth, native = load_inputs("demo", platforms, str(platforms))
+
+        self.assertEqual(
+            [f["name"] for f in pack_view["systems"]["nec-pc-88"]["files"]],
+            ["n88.rom", "N88EXT0.ROM"],
+        )
+        self.assertEqual(
+            [f["name"] for f in native["systems"]["nec-pc-88"]["files"]], ["n88.rom"]
+        )
+        self.assertEqual(
+            [f["destination"] for f in native["systems"]["tg16"]["files"]],
+            ["tg16/syscard3.pce"],
+        )
+        self.assertEqual(native["systems"]["nintendo-gamecube"]["files"], [])
+
+
+if __name__ == "__main__":
+    unittest.main()