fix: choose regions among the files required-only keeps

scripts/generate_pack.py

@@ -520,6 +520,7 @@ def _select_variants(
     source: str,
     regions,
     one_per_slot: bool,
+    required_only: bool = False,
 ) -> tuple[set, list, list]:
     """Which regional and slot alternatives this pack leaves out.
 
@@ -545,6 +546,7 @@ def _select_variants(
             target_cores=target_cores,
             include_extras=(source != "platform"),
             include_all=(source == "truth"),
+            required_only=required_only,
         )
     if regions:
         region_index = region_mod.build_region_index(emu_profiles or {})
@@ -704,7 +706,7 @@ def generate_pack(
     # direction. Runs only when --region is given.
     region_drops, region_fallbacks, slot_undecidable = _select_variants(
         config, pack_systems, emulators_dir, db, base_dest, emu_profiles,
-        target_cores, source, regions, one_per_slot,
+        target_cores, source, regions, one_per_slot, required_only,
     )
 
     with zipfile.ZipFile(zip_path, "w", zipfile.ZIP_DEFLATED) as zf:
@@ -3077,6 +3079,7 @@ def generate_manifest(
             target_cores=target_cores,
             include_extras=(source != "platform"),
             include_all=(source == "truth"),
+            required_only=required_only,
         )
         region_drops = region_mod.resolve_region_drops(
             region_groups, region_index, regions

scripts/packextras.py

@@ -626,6 +626,7 @@ def platform_region_groups(
     target_cores: set[str] | None = None,
     include_extras: bool = True,
     include_all: bool = False,
+    required_only: bool = False,
 ) -> tuple[dict[str, list[tuple[str, str]]], dict[tuple[str, str, str], str]]:
     """Group a platform's pack candidates the way region filtering reads them.
 
@@ -639,6 +640,10 @@ def platform_region_groups(
     for sys_id, system in systems.items():
         members = groups.setdefault(sys_id, [])
         for file_entry in system.get("files", []):
+            if required_only and file_entry.get("required") is False:
+                # Decided over what the pack keeps: an optional winner
+                # removed afterwards left its slot empty.
+                continue
             dest = sanitize_pack_path(
                 file_entry.get("destination", file_entry.get("name", ""))
             )
@@ -659,6 +664,8 @@ def platform_region_groups(
         target_cores=target_cores,
         include_all=include_all,
     ):
+        if required_only and extra.get("required") is False:
+            continue
         dest = sanitize_pack_path(extra.get("destination", extra.get("name", "")))
         if not dest:
             continue

tests/test_region_required_only.py

@@ -0,0 +1,39 @@
+"""--region decides among the files --required-only keeps.
+
+The regional choice ran over optional candidates too. In Batocera's Vic20
+group the optional Japanese kernel won for --region jp, the required PAL
+and NTSC kernels were dropped as beaten, and --required-only then removed
+the optional winner: the slot shipped empty.
+"""
+
+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"))
+
+
+class RequiredOnlyBeforeRegion(unittest.TestCase):
+    def test_optional_files_leave_the_groups(self):
+        from packextras import platform_region_groups
+
+        systems = {"vic20": {"files": [
+            {"name": "kernel-ntsc.bin", "destination": "Vic20/kernel-ntsc.bin", "required": True},
+            {"name": "kernel-japanese.bin", "destination": "Vic20/kernel-japanese.bin",
+             "required": False},
+        ]}}
+        groups, _ = platform_region_groups(
+            {}, systems, "emulators", None, "", {}, include_extras=False, required_only=True,
+        )
+        self.assertEqual(groups["vic20"], [("Vic20/kernel-ntsc.bin", "kernel-ntsc.bin")])
+
+    def test_every_caller_passes_it(self):
+        source = (REPO_ROOT / "scripts" / "generate_pack.py").read_text(encoding="utf-8")
+        self.assertEqual(source.count("required_only=required_only,\n        )"), 2)
+
+
+if __name__ == "__main__":
+    unittest.main()