chore: use modern package setup for example

Author: henryiii

source/tutorials/packaging-projects.rst

@@ -50,6 +50,7 @@ project's root directory - you will add content to them in the following steps.
     ├── example_pkg
     │   └── __init__.py
     ├── pyproject.toml
+    ├── setup.cfg
     ├── setup.py
     └── tests
 
@@ -93,12 +94,14 @@ always include it. If you were to use a different build system, such as
 would be completely different than the setuptools configuration described
 below. See :pep:`517` and :pep:`518` for background and details.
 
-Creating setup.py
------------------
 
-:file:`setup.py` is the build script for :ref:`setuptools`. It tells setuptools
-about your package (such as the name and version) as well as which code files
-to include.
+Creating setup.cfg
+------------------
+
+:file:`setup.cfg` is the configuration file for :ref:`setuptools`. It tells
+setuptools about your package (such as the name and version) as well as which
+code files to include. Eventually much of this configuration may be able to move
+to :file:`pyproject.toml`.
 
 Open :file:`setup.py` and enter the following content. Update the package name
 to include your username (for example, ``example-pkg-theacodes``), this ensures
@@ -107,55 +110,53 @@ packages uploaded by other people following this tutorial.
 
 .. code-block:: python
 
-    import setuptools
-
-    with open("README.md", "r", encoding="utf-8") as fh:
-        long_description = fh.read()
-
-    setuptools.setup(
-        name="example-pkg-YOUR-USERNAME-HERE", # Replace with your own username
-        version="0.0.1",
-        author="Example Author",
-        author_email="author@example.com",
-        description="A small example package",
-        long_description=long_description,
-        long_description_content_type="text/markdown",
-        url="https://github.com/pypa/sampleproject",
-        packages=setuptools.find_packages(),
-        classifiers=[
-            "Programming Language :: Python :: 3",
-            "License :: OSI Approved :: MIT License",
-            "Operating System :: OS Independent",
-        ],
-        python_requires='>=3.6',
-    )
-
-
-:func:`setup` takes several arguments. This example package uses a relatively
-minimal set:
+    [metadata]
+    # replace with your username:
+    name = example-pkg-YOUR-USERNAME-HERE
+    version = 0.0.1
+    url = https://github.com/pypa/sampleproject
+    author = Example Author
+    author_email = author@example.com
+    classifiers =
+        Programming Language :: Python :: 3
+        License :: OSI Approved :: MIT License
+        Operating System :: OS Independent
+    description = A small example package
+    long_description = file: README.md
+    long_description_content_type = text/markdown
+
+    [options]
+    python_requires = >=3.6
+
+
+There are a `variety of metadata and options
+<https://setuptools.readthedocs.io/en/latest/userguide/declarative_config.html>`_
+supported here. This is in configparser format; do not place quotes around values.
+This example package uses a relatively minimal set of options:
 
 - ``name`` is the *distribution name* of your package. This can be any name as
   long as only contains letters, numbers, ``_`` , and ``-``. It also must not
   already be taken on pypi.org. **Be sure to update this with your username,**
   as this ensures you won't try to upload a package with the same name as one
   which already exists when you upload the package.
 - ``version`` is the package version see :pep:`440` for more details on
-  versions.
+  versions. You can use ``file:`` or ``attr:`` directives to read from a file or
+  package attribute (simple attributes do not require import).
 - ``author`` and ``author_email`` are used to identify the author of the
   package.
 - ``description`` is a short, one-sentence summary of the package.
 - ``long_description`` is a detailed description of the package. This is
   shown on the package detail page on the Python Package Index. In
   this case, the long description is loaded from :file:`README.md` which is
-  a common pattern.
+  a common pattern, using the ``file:`` directive.
 - ``long_description_content_type`` tells the index what type of markup is
   used for the long description. In this case, it's Markdown.
 - ``url`` is the URL for the homepage of the project. For many projects, this
   will just be a link to GitHub, GitLab, Bitbucket, or similar code hosting
   service.
 - ``packages`` is a list of all Python :term:`import packages <Import
   Package>` that should be included in the :term:`Distribution Package`.
-  Instead of listing each package manually, we can use :func:`find_packages`
+  Instead of listing each package manually, we can use the ``find:`` directive
   to automatically discover all packages and subpackages. In this case, the
   list of packages will be ``example_pkg`` as that's the only package present.
 - ``classifiers`` gives the index and :ref:`pip` some additional metadata
@@ -169,6 +170,22 @@ minimal set:
 There are many more than the ones mentioned here. See
 :doc:`/guides/distributing-packages-using-setuptools` for more details.
 
+Creating setup.py (optional)
+----------------------------
+
+If you create a setup.py file, this will enable direct interaction with
+:file:`setup.py` (which generally should be avoided), and editable installs. This file
+used to be required, but can be omitted in modern setuptools.
+
+Anything you set in setup.cfg can instead be set via keyword argument to
+:func:`setup()`; this enables computed values to be used. You will also need
+:func:`setup()` for setting up extension modules for compilation.
+
+.. code-block:: python
+
+    import setuptools
+
+    setuptools.setup()
 
 Creating README.md
 ------------------