fix: let A pass over system and recycle folders

install.py

@@ -11056,6 +11056,33 @@ def _browse_rows(folder: Path | None, zips: bool = False) -> tuple[list[TuiRow],
     return rows, ""
 
 
+# The folders of a system root that hold no one's files: A went into
+# /bin from /, the first name in order.
+_POSIX_ROOT_SYSTEM = frozenset((
+    "bin", "boot", "dev", "efi", "etc", "lib", "lib32", "lib64", "libx32", "lost+found",
+    "proc", "root", "run", "sbin", "snap", "srv", "sys", "tmp", "usr", "var",
+))
+# FILE_ATTRIBUTE_HIDDEN and FILE_ATTRIBUTE_SYSTEM: Explorer shows neither.
+_WINDOWS_HIDDEN = 0x2 | 0x4
+
+
+def _system_folder(path: Path, folder: Path) -> bool:
+    """A folder of the system, not one a person keeps files in: the
+    recycle bin and restore points of a Windows drive ($RECYCLE.BIN, System
+    Volume Information, hidden by Explorer), and /bin, /etc, /usr and the
+    like at the root of a Unix system."""
+    name = path.name
+    if name.startswith(("$", ".")) or name.casefold() == "system volume information":
+        return True
+    try:
+        attributes = getattr(os.stat(path, follow_symlinks=False), "st_file_attributes", 0)
+    except OSError:
+        attributes = 0
+    if attributes & _WINDOWS_HIDDEN:
+        return True
+    return folder == Path("/") and name in _POSIX_ROOT_SYSTEM
+
+
 def _browse_to(state: TuiState, folder: Path | None, came_from: Path | None = None) -> None:
     state.browse_dir = folder
     state.browse_rows, state.status = _browse_rows(folder, state.browse_for == "from")
@@ -11070,7 +11097,7 @@ def _browse_to(state: TuiState, folder: Path | None, came_from: Path | None = No
         focus = next((index for index, row in enumerate(state.browse_rows)
                       if row.action == "dir" and isinstance(row.value, Path)
                       and row.label == f"{row.value.name}/"
-                      and not row.value.name.startswith(".")), 0)
+                      and not _system_folder(row.value, folder)), 0)
         if not focus and not state.status:
             state.status = ("This is your home folder: no setup reads its BIOS files "
                             "here. Go back to type a path." if folder == state.home

tests/test_install_tui.py

@@ -3843,5 +3843,52 @@ class TheFolderScreenSaysWhatItOffers(unittest.TestCase):
                 self.assertEqual(rows[state.focus["folder"]].action, "browse")
 
 
+class AFocusesNoSystemFolder(unittest.TestCase):
+    """At / A went into bin/, and at a drive root holding $RECYCLE.BIN into
+    the recycle bin, which Use this folder then took as the BIOS folder."""
+
+    def setUp(self):
+        self.home = Path(tempfile.mkdtemp(dir=REPO_ROOT / "tmp"))
+        self.addCleanup(shutil.rmtree, self.home, True)
+        self.state = install.TuiState(os_type="linux", home=self.home)
+        self.state.platform = "retroarch"
+        self.state.stack = ["folder", "browse"]
+
+    def focused(self) -> install.TuiRow:
+        return self.state.browse_rows[self.state.focus["browse"]]
+
+    def test_the_recycle_bin_and_restore_points_are_passed_over(self):
+        for name in ("$RECYCLE.BIN", "System Volume Information", "Games"):
+            (self.home / name).mkdir()
+        with mock.patch.object(install, "_mounted_cards", return_value=[]):
+            install._browse_to(self.state, self.home)
+        self.assertEqual(self.focused().label, "Games/")
+
+    def test_explorer_hidden_folders_are_passed_over(self):
+        for name in ("Boot", "Games"):
+            (self.home / name).mkdir()
+        real_stat = os.stat
+
+        def stat(path, *args, **kwargs):
+            result = real_stat(path, *args, **kwargs)
+            hidden = 0x2 | 0x4 if Path(path).name == "Boot" else 0
+            return types.SimpleNamespace(st_file_attributes=hidden, st_mode=result.st_mode)
+
+        with mock.patch.object(install, "_mounted_cards", return_value=[]), \
+                mock.patch.object(install.os, "stat", stat):
+            install._browse_to(self.state, self.home)
+        self.assertEqual(self.focused().label, "Games/")
+
+    def test_at_the_root_no_system_folder_is_focused(self):
+        with mock.patch.object(install, "_mounted_cards", return_value=[]):
+            install._browse_to(self.state, Path("/"))
+        row = self.focused()
+        if row.action == "dir":
+            self.assertNotIn(row.value.name, install._POSIX_ROOT_SYSTEM)
+        names = {r.value.name for r in self.state.browse_rows if r.action == "dir"}
+        if "bin" in names and names - install._POSIX_ROOT_SYSTEM - {""}:
+            self.assertEqual(row.action, "dir")
+
+
 if __name__ == "__main__":
     unittest.main()