add ENOTDIR to from_file silent error handling

CHANGES.rst

@@ -23,6 +23,8 @@ Unreleased
     switching ``POST`` to ``GET``. This preserves the current behavior of
     ``GET`` and ``POST`` redirects, and is also correct for frontend libraries
     such as HTMX. :issue:`5895`
+-   ``Config.from_file()`` with ``silent=True`` handles ``ENOTDIR`` errors,
+    matching the behavior of ``Config.from_pyfile()``. :issue:`5912`
 
 
 Version 3.1.2

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 +195,20 @@ def test_config_missing_file():
     assert not app.config.from_file("missing.json", load=json.load, silent=True)
 
 
+def test_config_from_file_enotdir(tmp_path):
+    not_a_dir = tmp_path / "not_a_dir"
+    not_a_dir.write_text("")
+    app = flask.Flask(__name__)
+    app.config.root_path = str(tmp_path)
+
+    with pytest.raises(OSError):
+        app.config.from_file("not_a_dir/config.json", load=json.load)
+
+    assert not app.config.from_file(
+        "not_a_dir/config.json", load=json.load, silent=True
+    )
+
+
 def test_custom_config_class():
     class Config(flask.Config):
         pass