fix: index regions over the platform's own cores

tests/test_region_platform_index.py

@@ -0,0 +1,44 @@
+"""A platform's region filter listens to the emulators it runs only.
+
+The index was built over every profile: Pizza Boy SC, an Android app no
+frontend here runs as a core, declares bios_CD_E.bin without a region, which
+voided the [europe] tag Genesis Plus GX and PicoDrive give it, and
+`--region us` kept both foreign Mega-CD BIOSes in the RetroArch pack.
+"""
+
+from __future__ import annotations
+
+import sys
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(REPO_ROOT / "scripts"))
+
+import region as region_mod  # noqa: E402
+
+PROFILES = {
+    "gpgx": {"emulator": "GPGX", "type": "libretro", "systems": ["sega-mega-cd"],
+             "files": [{"name": "bios_CD_E.bin", "region": ["europe"]}]},
+    "pizza": {"emulator": "Pizza", "type": "standalone", "systems": ["sega-mega-cd"],
+              "files": [{"name": "bios_CD_E.bin"}]},
+}
+
+
+class OnlyThePlatformsCores(unittest.TestCase):
+    def test_a_foreign_untagged_entry_does_not_void_the_tag(self):
+        config = {"cores": ["gpgx"], "systems": {"sega-mega-cd": {"files": []}}}
+        index = region_mod.platform_region_index(config, PROFILES)
+        self.assertFalse(index["bios_CD_E.bin"]["has_untagged"])
+        self.assertTrue(region_mod.build_region_index(PROFILES)["bios_CD_E.bin"]["has_untagged"])
+
+    def test_every_platform_site_reads_it(self):
+        for module in ("verify.py", "generate_pack.py", "packverify.py"):
+            source = (REPO_ROOT / "scripts" / module).read_text(encoding="utf-8")
+            self.assertNotIn("build_region_index(emu_profiles", source, module)
+            self.assertNotIn("build_region_index(profiles)", source, module)
+            self.assertIn("platform_region_index(", source, module)
+
+
+if __name__ == "__main__":
+    unittest.main()