fix: read retroarch.cfg for cores in a --dest run

A run given --dest, as every interface run is, never read the config
naming libretro_directory, so only installed cores found none where line
mode found them. core_dirs now asks _retroarch_config_for, as the save
directory does, and the advice to drop --dest goes.

install.py

@@ -2302,11 +2302,12 @@ def core_dirs(plat: str, bios_path: Path) -> list[Path]:
     """The directories the RetroArch writing to bios_path loads cores from.
 
     The config detection read for this system directory names them in
-    libretro_directory. Without one, a retroarch.cfg beside the system
+    libretro_directory, read here when the run was given --dest, as the
+    interface's runs all are. Without one, a retroarch.cfg beside the system
     directory is the portable layout. Unset, the setting is cores/ under
     RetroArch's own directory.
     """
-    found = _RETROARCH_CONFIGS.get(bios_path)
+    found = _retroarch_config_for(bios_path)
     if found is None and (bios_path.parent / "retroarch.cfg").is_file():
         found = (bios_path.parent / "retroarch.cfg", bios_path.parent)
     dirs: list[Path] = []
@@ -3979,9 +3980,10 @@ def _retroarch_config_for(bios_path: Path) -> tuple[Path, Path] | None:
     folder ':' expands to there.
 
     A run given --dest detects nothing, so the configs are read here, once
-    and silently, the first time a save directory is asked for: the
-    interface names every folder with --dest, and its runs sent Azahar's
-    keys.txt to a guessed folder where line mode read savefile_directory.
+    and silently, the first time a save directory or the cores folder is
+    asked for: the interface names every folder with --dest, and its runs
+    sent Azahar's keys.txt to a guessed folder where line mode read
+    savefile_directory, and found no core where line mode found them.
     """
     found = _RETROARCH_CONFIGS.get(bios_path)
     if found is not None or _CONFIGS_READ:
@@ -8713,12 +8715,12 @@ def _missing_dest(dest: Path, ask: bool, named: str = "named with --dest") -> No
             sys.exit(2)
 
 
-def _no_core_found(plat: str, bios_path: Path, searched: list[Path], dest_given: bool) -> None:
+def _no_core_found(plat: str, bios_path: Path, searched: list[Path]) -> None:
     """Refuse --installed-cores with no core, and say how to point at them.
 
-    With --dest, detection does not run, and without a retroarch.cfg beside
-    the folder nothing names the cores folder: the run stopped on "no known
-    directory" with no way forward.
+    With no retroarch.cfg naming the folder as its system_directory, and
+    none beside it, nothing names the cores folder: the run stopped on "no
+    known directory" with no way forward.
     """
     where = (f"none in {', '.join(map(str, searched))}" if searched
              else f"no retroarch.cfg was found for {bios_path} to name their folder")
@@ -8728,9 +8730,6 @@ def _no_core_found(plat: str, bios_path: Path, searched: list[Path], dest_given:
           "retroarch.cfg, cores/ beside RetroArch by default):", file=sys.stderr)
     command = _INVOCATION.command(plat, bios_path, without=("--installed-cores", "--cores-dir"))
     print(f"    {command} --cores-dir <cores folder>", file=sys.stderr)
-    if dest_given:
-        print("  Or run it without --dest: detection reads retroarch.cfg, which names "
-              "that folder.", file=sys.stderr)
     print("  Or run it without --installed-cores to install every file.", file=sys.stderr)
     sys.exit(1)
 
@@ -9156,7 +9155,7 @@ def _install(args: argparse.Namespace, real_stdout: TextIO) -> None:
             )
             sys.exit(1)
         if args.installed_cores and not cores_found[(plat_name, bios_path)]:
-            _no_core_found(plat_name, bios_path, searched, bool(args.dest))
+            _no_core_found(plat_name, bios_path, searched)
 
     for plat_name, bios_path in platforms:
         if bios_path not in installed_paths:

tests/test_install_cores.py

@@ -488,5 +488,39 @@ class TheOneLinerReadsInstalledCores(unittest.TestCase):
             self.assertEqual(repo.installed(), ["gba_bios.bin", "mgba/extra.bin"])
 
 
+class TheInterfaceFindsTheCoresLineModeFinds(unittest.TestCase):
+    """The interface names the BIOS folder with --dest, so its runs never
+    read retroarch.cfg: "only installed cores" found none where line mode,
+    detecting the same config, found them (macOS, Flatpak, any custom
+    system_directory)."""
+
+    def test_a_config_away_from_the_bios_folder(self):
+        with _CoreRepository() as repo:
+            (repo.root / "retroarch.cfg").unlink()
+            home = repo.root / "home"
+            config = home / ".config" / "retroarch"
+            config.mkdir(parents=True)
+            cores = repo.root / "elsewhere" / "my cores"
+            cores.mkdir(parents=True)
+            (cores / "mgba_libretro.so").write_bytes(b"")
+            (config / "retroarch.cfg").write_text(
+                f'system_directory = "{repo.dest}"\n'
+                f'libretro_directory = "{cores}"\n')
+            env = {**repo.env(), "HOME": str(home), "RETROBIOS_OS": "linux",
+                   "XDG_CONFIG_HOME": str(home / ".config")}
+            repo.dest.mkdir()
+            found = []
+            for given in ((), ("--dest", str(repo.dest))):
+                command = [sys.executable, str(REPO_ROOT / "install.py"), "--platform",
+                           "retroarch", *given, "--installed-cores", "--check"]
+                proc = subprocess.run(command, env=env, capture_output=True, text=True,
+                                      timeout=60, check=False, stdin=subprocess.DEVNULL)
+                self.assertNotIn("no installed core found", proc.stderr)
+                found.append([line for line in proc.stdout.splitlines()
+                              if "core installed" in line or "Narrowed" in line])
+            self.assertEqual(found[0], found[1])
+            self.assertIn("  1 core installed", found[1])
+
+
 if __name__ == "__main__":
     unittest.main()

wiki/installer.md

@@ -628,9 +628,10 @@ rather than read as having no game data.
 `--installed-cores` reads the cores a RetroArch already has and installs what
 they need. The cores are the `<name>_libretro.so` (`.dll`, `.dylib`,
 `_libretro_android.so`) files in the `libretro_directory` of the
-`retroarch.cfg` detection found, `cores/` beside RetroArch when the setting is
-unset, a `retroarch.cfg` next to the system directory for a portable install
-given with `--dest`, and the folders RetroPie (`/opt/retropie/libretrocores`)
+`retroarch.cfg` whose `system_directory` is the BIOS folder, found the same
+way with `--dest` or without, `cores/` beside RetroArch when the setting is
+unset, a `retroarch.cfg` next to the system directory for a portable install,
+and the folders RetroPie (`/opt/retropie/libretrocores`)
 and Lakka (`/usr/lib/libretro`, `/storage/cores`) install into. A core file
 is named the buildbot's way (`mednafen_psx`), and the manifest maps each name to
 the profile its files are filed under (`beetle_psx`).