Add pyproject.toml & modern packaging to introduction.

README.rst

@@ -50,7 +50,8 @@ Example usage for ``pip-compile``
 =================================
 
 The ``pip-compile`` command lets you compile a ``requirements.txt`` file from
-your dependencies, specified in either ``setup.py`` or ``requirements.in``.
+your dependencies, specified in either ``pyproject.toml``, ``setup.cfg``,
+``setup.py``, or ``requirements.in``.
 
 Run it with ``pip-compile`` or ``python -m piptools compile``. If you use
 multiple Python versions, you can also run ``py -X.Y -m piptools compile`` on
@@ -67,39 +68,62 @@ available. To compile from scratch, first delete the existing
 ``requirements.txt`` file, or see `Updating requirements`_ for alternative
 approaches.
 
-Requirements from ``setup.py``
-------------------------------
+Requirements from ``pyproject.toml``
+------------------------------------
 
-Suppose you have a Django project, and want to pin it for production.
-If you have a ``setup.py`` with ``install_requires=['django']``, then run
-``pip-compile`` without any arguments:
+The ``pyproject.toml`` file is the
+`latest standard <https://peps.python.org/pep-0621/>`_ for configuring
+packages and applications and recommended for new projects. ``pip-compile``
+supports both installing your ``project.dependencies`` as well as your
+``project.optional-dependencies``. Thanks to the fact that this is an
+official standard, you can use ``pip-compile`` to pin your dependencies
+for projects based on modern standards-adhering packaging tools like
+`Hatch <https://hatch.pypa.io/>`_ or `flit <https://flit.pypa.io/>`_.
+
+Suppose you have a Django project that is packaged using ``Hatch``, and you
+want to pin it for production. You also want to pin your development tools
+into a separate pin file. You declare ``django`` as a dependency and create an
+optional dependency ``dev`` that includes ``pytest``:
+
+.. code-block:: toml
+
+    [build-system]
+    requires = ["hatchling"]
+    build-backend = "hatchling.build"
+
+    [project]
+    name = "my-cool-django-app"
+    version = "42"
+    dependencies = ["django"]
+
+    [project.optional-dependencies]
+    dev = ["pytest"]
+
+You can produce your pin files as easily as:
 
 .. code-block:: bash
 
-    $ pip-compile
-    #
-    # This file is autogenerated by pip-compile
-    # To update, run:
-    #
-    #    pip-compile
-    #
-    asgiref==3.2.3
-        # via django
-    django==3.0.3
-        # via my_django_project (setup.py)
-    pytz==2019.3
-        # via django
-    sqlparse==0.3.0
-        # via django
+    $ pip-compile -o requirements.txt pyproject.toml
+    $ pip-compile --extra dev -o dev-requirements.txt pyproject.toml
+
+This is great for both pinning your applications, but also to keep the CI
+of your open-source Python package stable.
+
+Requirements from ``setup.py`` and ``setup.cfg``
+------------------------------------------------
 
-``pip-compile`` will produce your ``requirements.txt``, with all the Django
-dependencies (and all underlying dependencies) pinned.
+``pip-compile`` has also full support for ``setup.py``- and
+``setup.cfg``-based projects that drive setuptools.
 
-Without ``setup.py``
---------------------
+Just define your dependencies and extras as usual and run
+``pip-compile`` as above.
 
-If you don't use ``setup.py`` (`it's easy to write one`_), you can create a
-``requirements.in`` file to declare the Django dependency:
+``requirements.in``
+-------------------
+
+You can also use plain text files for your requirements (e.g. if you don't
+want your application to be a package). To use a ``requirements.in`` file to
+declare the Django dependency:
 
 .. code-block:: ini
 
@@ -129,15 +153,13 @@ Now, run ``pip-compile requirements.in``:
 And it will produce your ``requirements.txt``, with all the Django dependencies
 (and all underlying dependencies) pinned.
 
-.. _it's easy to write one: https://packaging.python.org/guides/distributing-packages-using-setuptools/#configuring-your-project
-
 .. _Updating requirements:
 
 Updating requirements
 ---------------------
 
 ``pip-compile`` generates a ``requirements.txt`` file using the latest versions
-that fulfil the dependencies of ``setup.py`` or ``requirements.in``.
+that fulfil the dependencies you specify in the supported files.
 
 If ``pip-compile`` finds an existing ``requirements.txt`` file that fulfils the
 dependencies then no changes will be made, even if updates are available.