req: Do not require toml with Python >= 3.11

Python 3.11 ships with the `tomllib` package in the standard library.
The optional dependency on `toml` is thus not necessary. Docs were
updated to simplify the installation, supposing that most users have
Python 3.11 or a later version.

docs/installation.rst

@@ -9,22 +9,21 @@ Install with ``pip``, preferably in a `virtual environment`_:
 
     $ python3 -m venv /path/to/your/virtualenv
     $ source /path/to/your/virtualenv/bin/activate
-    $ pip install "check-oldies[toml]"
-
+    $ pip install "check-oldies"
 
 .. note::
 
-    If you do not need to read TOML configuration files, you may omit the
-    optional dependency and install like this:
+    If you want to read TOML configuration files **and if you have
+    Python 3.10 or earlier**, you must install an optional dependency,
+    like this:
 
     .. code-block:: bash
 
-        $ pip install check-oldies
+        $ pip install "check-oldies[toml]"
 
     Configuration files are not required, but some options are only
-    available through configuration files. If you are not sure, do not
-    use the latter command. Instead, use ``pip install check-oldies[toml]``
-    as indicated above.
+    available through them. If you are not sure, use the latter
+    command.
 
 
 .. _virtual environment: https://packaging.python.org/tutorials/installing-packages/#creating-virtual-environments

setup.cfg

@@ -43,6 +43,7 @@ console-scripts =
     forget-me-not = check_oldies.forget_me_not:main
 
 [options.extras_require]
+# This is only needed for Python < 3.11.
 toml = toml
 
 [options.packages.find]

src/check_oldies/compat.py

@@ -1,4 +1,5 @@
 import enum
+import pathlib
 
 
 __all__ = ["StrEnum"]
@@ -36,3 +37,19 @@ def __new__(cls, *values):
         def _generate_next_value_(name, start, count, last_values):
             return name.lower()
     # fmt: on
+
+
+try:
+    import tomllib
+
+    def load_toml(path: pathlib.Path) -> dict:
+        with open(path, "rb") as fp:
+            return tomllib.load(fp)
+except ImportError: # Python < 3.11
+    try:
+        import toml
+
+        def load_toml(path: pathlib.Path) -> dict:
+            return toml.load(path)
+    except ImportError:
+        load_toml = None

src/check_oldies/configuration.py

@@ -2,11 +2,7 @@
 import subprocess
 import sys
 
-
-try:
-    import toml
-except ImportError:  # pragma: no cover
-    toml = None
+from . import compat
 
 
 PYPROJECT_FILENAME = "pyproject.toml"
@@ -34,13 +30,14 @@ def replace_dashes(options):
 
 
 def read_from_configuration_file(path, tool_name):
-    if not toml:  # pragma: no cover
+    if not compat.load_toml:  # pragma: no cover
         sys.exit(
             'You must install with `pip install "check-oldies[toml]" '
-            "to read from TOML configuration files."
+            "to read TOML configuration files."
         )
+
     try:
-        conf = toml.load(path)
+        conf = compat.load_toml(path)
     except Exception as exc:  # pylint: disable=broad-except # pragma: no cover
         sys.exit(f"Error reading {path}: {exc.args[-1]}")