methof ans tests

rich/_fileno.py

@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+from typing import IO, Callable
+
+
+def get_fileno(file_like: IO[str]) -> int | None:
+    """Get fileno() from a file, accounting for poorly implemented file-like objects.
+
+    Args:
+        file_like (IO): A file-like object.
+
+    Returns:
+        int | None: The result of fileno if available, or None if operation failed.
+    """
+    fileno: Callable[[], int] | None = getattr(file_like, "fileno", None)
+    if fileno is not None:
+        try:
+            return fileno()
+        except Exception:
+            # `fileno` is documented as potentially raising a OSError
+            # Alas, from the issues, there are so many poorly implemented file-like objects,
+            # that `fileno()` can raise just about anything.
+            return None
+    return None

tests/test_getfileno.py

@@ -0,0 +1,25 @@
+from rich._fileno import get_fileno
+
+
+def test_get_fileno():
+    class FileLike:
+        def fileno(self) -> int:
+            return 123
+
+    assert get_fileno(FileLike()) == 123
+
+
+def test_get_fileno_missing():
+    class FileLike:
+        pass
+
+    assert get_fileno(FileLike()) is None
+
+
+def test_get_fileno_broken():
+    class FileLike:
+        def fileno(self) -> int:
+            1 / 0
+            return 123
+
+    assert get_fileno(FileLike()) is None