fix: place MAME 2016 and older sets by the game

MAME 2000, 2003, 2003-Plus, 2009, 2010, 2014, 2015, 2016 and UME 2015
search the folder of the loaded game for their sets and never the system
folder: osd_get_path gives FILETYPE_ROM the content path (mame2003 and
mame2003-plus src/fileio.c:217-220), -rompath is MgamePath (mame2009
retromain.c:432-434, mame2014 retromain.c:1851-1856, mame2015 and
ume2015 retromain.c:1980-2042, mame2016 retromain.cpp:1364-1402), ROMs
open with libretro_content_directory (mame2010 romload.c:667-685) or
IMAMEBASEPATH (mame2000 libretro.c:1044-1053, 1247). Their 421 sets are
load_from: content_dir. Samples, artwork, cheats and the data files read
from the system folder keep their paths.

A set read beside the game goes to the roms folder of each system the
platform launches the core for: libretro_systems, the default core of a
rom folder, the cores a system offers under its own name, the systems a
RetroPie package registers (the lr-mess packages build SUBTARGET=mess,
lr-mess2016.sh:31, and read none of these arcade sets). A roms root in
the install tree takes a plain dest, as a standalone entry placed there.
A platform with no folder per system, or none it can place (RetroArch,
Lakka, RetroBat, EmuDeck, MyMinUI), names the set as read outside the
BIOS folder. EmulatorJS writes the BIOS and the game to one folder
(emulator.js:845, 990, 1054): RomM keeps its firmware entries. Game data
read beside the content is left to the game.

Manifests: roms folders gain 408 files on RetroDECK, 182 on RetroPie,
179 on Recalbox, 140 on AmberELEC, 134 on KNULLI, 52 on Batocera and
ROCKNIX, 39 on EmuELEC. BIOS root copies no other core reads leave: 80
on RetroArch, Lakka and ROCKNIX, 61 on EmuELEC, 60 on Recalbox, 59 on
AmberELEC, 57 on RetroPie, 26 on MyMinUI, 20 on RetroDECK, 19 on
Batocera and EmuDeck, 16 on KNULLI, 13 on RetroBat. verify --all keeps
its severity and status counts.

tests/test_launcher_placement.py

@@ -993,8 +993,17 @@ class AdvanceMameOnEmuELEC(unittest.TestCase):
                 str(REPO_ROOT / "platforms" / "_registry.yml"),
                 emulators_dir=str(REPO_ROOT / "emulators"), offline=True,
             )
-        by_dest = {f["dest"]: f["sha1"] for f in manifest["files"]}
-        sets = [d.removeprefix("arcade/") for d in by_dest if d.startswith("arcade/")]
+        # mame2003_plus reads its own sets in arcade/ too (es_systems.cfg):
+        # the copy AdvanceMAME reads there is the one its claim names.
+        def advancemame_copy(entry: dict) -> str | None:
+            for copy in (entry, *(entry.get("alternatives") or [])):
+                if "advancemame" in (copy.get("cores") or []):
+                    return copy["sha1"]
+            return None
+
+        by_dest = {f["dest"]: advancemame_copy(f) for f in manifest["files"]}
+        sets = [d.removeprefix("arcade/") for d, sha1 in by_dest.items()
+                if d.startswith("arcade/") and sha1]
         self.assertEqual(len(sets), 29)
         for name in sets:
             self.assertEqual(by_dest["arcade/" + name], by_dest["mame/" + name], name)
@@ -1015,5 +1024,80 @@ class AdvanceMameOnEmuELEC(unittest.TestCase):
         self.assertNotIn("/MAME/", moved)
 
 
+def libretro_view(emulator: str, platform: str) -> dict:
+    profile = load_emulator_profiles(str(REPO_ROOT / "emulators"))[emulator]
+    config = load_platform_config(platform, str(REPO_ROOT / "platforms"))
+    (view,) = [v for v, standalone in platform_layouts(emulator, profile, standalone_set(config))
+               if not standalone]
+    return view
+
+
+class SetsReadBesideTheGame(unittest.TestCase):
+    """MAME 2016 and older search the folder of the loaded game for their
+    sets and never the system folder (mame2003 src/fileio.c:217-220,
+    mame2010 src/emu/romload.c:667-685, mame2016
+    src/osd/retro/retromain.cpp:1364-1402)."""
+
+    CORES = ("mame2000", "mame2003", "mame2003_plus", "mame2009", "mame2010",
+             "mame2014", "mame2015", "mame2016", "ume2015")
+
+    def test_each_set_is_read_beside_the_game(self) -> None:
+        profiles = load_emulator_profiles(str(REPO_ROOT / "emulators"))
+        for key in self.CORES:
+            sets = [f for f in profiles[key]["files"] if f.get("category") == "bios_zip"]
+            self.assertTrue(sets, key)
+            for entry in sets:
+                self.assertEqual(entry.get("load_from"), "content_dir", (key, entry["name"]))
+
+    def test_batocera_places_them_in_the_folders_it_launches_the_core_for(self) -> None:
+        # es_systems.yml offers mame078plus under mame and neogeo.
+        view = libretro_view("mame2003_plus", "batocera")
+        neogeo = [e for e in view["files"] if e["name"] == "neogeo.zip"]
+        self.assertEqual(sorted(e["path"] for e in neogeo), ["mame/neogeo.zip", "neogeo/neogeo.zip"])
+        self.assertTrue(all(e["root"] == "roms" and "load_from" not in e for e in neogeo))
+
+    def test_retroarch_names_them_outside_the_bios_folder(self) -> None:
+        # RetroArch keeps no folder per system: the game's folder is the user's.
+        view = libretro_view("mame2003", "retroarch")
+        sets = [e for e in view["files"] if e.get("category") == "bios_zip"]
+        self.assertTrue(sets)
+        self.assertTrue(all(e.get("unplaced") == "outside_bios_folder" for e in sets))
+
+    def test_game_data_beside_the_content_is_left_to_the_game(self) -> None:
+        view = libretro_view("mame2000", "retroarch")
+        (hiscore,) = [e for e in view["files"] if e["name"] == "hiscore.dat"]
+        self.assertEqual(hiscore.get("load_from"), "content_dir")
+        self.assertNotIn("unplaced", hiscore)
+
+    def test_a_mess_build_takes_no_arcade_set(self) -> None:
+        # lr-mess2016 builds mame2016 with SUBTARGET=mess (lr-mess2016.sh:31).
+        view = libretro_view("mame2016", "retropie")
+        folders = {e["path"].split("/")[0] for e in view["files"] if e.get("root") == "roms"}
+        self.assertEqual(folders, {"arcade", "mame-libretro"})
+
+    def test_emulatorjs_writes_the_bios_beside_the_game(self) -> None:
+        # data/src/emulator.js:845, 990, 1054: one filesystem root for both.
+        view = libretro_view("mame2003_plus", "romm")
+        sets = [e for e in view["files"] if e.get("category") == "bios_zip"]
+        self.assertTrue(all("load_from" not in e and "root" not in e for e in sets))
+
+    def test_the_manifest_drops_the_root_copy_no_core_reads(self) -> None:
+        from common import load_database
+
+        db = load_database(str(REPO_ROOT / "database.json"))
+        with redirect_stdout(io.StringIO()):
+            manifest = generate_manifest(
+                "rocknix", str(REPO_ROOT / "platforms"), db, str(REPO_ROOT / "bios"),
+                str(REPO_ROOT / "platforms" / "_registry.yml"),
+                emulators_dir=str(REPO_ROOT / "emulators"), offline=True,
+            )
+        dests = {(f.get("root") or "", f["dest"]) for f in manifest["files"]}
+        # ROCKNIX starts mame2003_plus for arcade and mame (arcade.conf, mame.conf),
+        # and no core it runs reads coh1000c.zip at the BIOS root.
+        self.assertIn(("roms", "arcade/coh1000c.zip"), dests)
+        self.assertIn(("roms", "mame/coh1000c.zip"), dests)
+        self.assertNotIn(("", "coh1000c.zip"), dests)
+
+
 if __name__ == "__main__":
     unittest.main()