add text parameter to config.from_file

CHANGES.rst

@@ -33,6 +33,8 @@ Unreleased
 -   Use modern packaging metadata with ``pyproject.toml`` instead of ``setup.cfg``.
     :pr:`4947`
 -   Ensure subdomains are applied with nested blueprints. :issue:`4834`
+-   ``config.from_file`` can use ``text=False`` to indicate that the parser wants a
+    binary file instead. :issue:`4989`
 
 
 Version 2.2.3

src/flask/config.py

@@ -234,6 +234,7 @@ class Config(dict):
         filename: str,
         load: t.Callable[[t.IO[t.Any]], t.Mapping],
         silent: bool = False,
+        text: bool = True,
     ) -> bool:
         """Update the values in the config from a file that is loaded
         using the ``load`` parameter. The loaded data is passed to the
@@ -244,8 +245,8 @@ class Config(dict):
             import json
             app.config.from_file("config.json", load=json.load)
 
-            import toml
+            import tomllib
-            app.config.from_file("config.toml", load=toml.load)
+            app.config.from_file("config.toml", load=tomllib.load, text=False)
 
         :param filename: The path to the data file. This can be an
             absolute path or relative to the config root path.
@@ -254,14 +255,18 @@ class Config(dict):
         :type load: ``Callable[[Reader], Mapping]`` where ``Reader``
             implements a ``read`` method.
         :param silent: Ignore the file if it doesn't exist.
+        :param text: Open the file in text or binary mode.
         :return: ``True`` if the file was loaded successfully.
 
+        .. versionchanged:: 2.3
+            The ``text`` parameter was added.
+
         .. versionadded:: 2.0
         """
         filename = os.path.join(self.root_path, filename)
 
         try:
-            with open(filename) as f:
+            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):

tests/static/config.toml

@@ -0,0 +1,2 @@
+TEST_KEY="foo"
+SECRET_KEY="config"

tests/test_config.py

@@ -6,7 +6,6 @@ import pytest
 
 import flask
 
-
 # config keys used for the TestConfig
 TEST_KEY = "foo"
 SECRET_KEY = "config"
@@ -30,13 +29,23 @@ def test_config_from_object():
     common_object_test(app)
 
 
-def test_config_from_file():
+def test_config_from_file_json():
     app = flask.Flask(__name__)
     current_dir = os.path.dirname(os.path.abspath(__file__))
     app.config.from_file(os.path.join(current_dir, "static", "config.json"), json.load)
     common_object_test(app)
 
 
+def test_config_from_file_toml():
+    tomllib = pytest.importorskip("tomllib", reason="tomllib added in 3.11")
+    app = flask.Flask(__name__)
+    current_dir = os.path.dirname(os.path.abspath(__file__))
+    app.config.from_file(
+        os.path.join(current_dir, "static", "config.toml"), tomllib.load, text=False
+    )
+    common_object_test(app)
+
+
 def test_from_prefixed_env(monkeypatch):
     monkeypatch.setenv("FLASK_STRING", "value")
     monkeypatch.setenv("FLASK_BOOL", "true")