Fix Config.from_file() silent mode not handling ENOTDIR

`Config.from_file()` with `silent=True` did not handle `errno.ENOTDIR`,
causing it to raise an error when a path component is a regular file
instead of a directory. This was inconsistent with `Config.from_pyfile()`,
which has handled ENOTDIR since PR #2581.

fixes #5912

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGES.rst

@@ -3,6 +3,9 @@ Version 3.2.0
 
 Unreleased
 
+-   ``Config.from_file()`` with ``silent=True`` now handles ``ENOTDIR``
+    errors, matching the behavior of ``Config.from_pyfile()``. :issue:`5912`
+
 -   Drop support for Python 3.9. :pr:`5730`
 -   Remove previously deprecated code: ``__version__``. :pr:`5648`
 -   ``RequestContext`` has merged with ``AppContext``. ``RequestContext`` is now

src/flask/config.py

@@ -293,7 +293,7 @@ class Config(dict):  # type: ignore[type-arg]
             with open(filename, "r" if text else "rb") as f:
                 obj = load(f)
         except OSError as e:
-            if silent and e.errno in (errno.ENOENT, errno.EISDIR):
+            if silent and e.errno in (errno.ENOENT, errno.EISDIR, errno.ENOTDIR):
                 return False
 
             e.strerror = f"Unable to load configuration file ({e.strerror})"

tests/test_config.py

@@ -195,6 +195,28 @@ def test_config_missing_file():
     assert not app.config.from_file("missing.json", load=json.load, silent=True)
 
 
+def test_config_enotdir_from_pyfile(tmp_path):
+    """from_pyfile with silent=True handles ENOTDIR when a path
+    component is a regular file rather than a directory."""
+    # Create a regular file that will block directory traversal.
+    blocker = tmp_path / "not_a_dir"
+    blocker.write_text("x")
+    app = flask.Flask(__name__)
+    # Trying to open "not_a_dir/settings.cfg" raises ENOTDIR.
+    assert not app.config.from_pyfile(str(blocker / "settings.cfg"), silent=True)
+
+
+def test_config_enotdir_from_file(tmp_path):
+    """from_file with silent=True handles ENOTDIR when a path
+    component is a regular file rather than a directory."""
+    blocker = tmp_path / "not_a_dir"
+    blocker.write_text("x")
+    app = flask.Flask(__name__)
+    assert not app.config.from_file(
+        str(blocker / "config.json"), load=json.load, silent=True
+    )
+
+
 def test_custom_config_class():
     class Config(flask.Config):
         pass