Merge pull request #1371 from sinoroc/add-modernize-setup-py-project

Add page "How to modernize a setup.py project?"

Author: willingc

source/discussions/setup-py-deprecated.rst

@@ -105,10 +105,6 @@ Although the usage of :file:`setup.py` as an executable script is deprecated,
 its usage as a configuration file for setuptools is absolutely fine.
 There is likely no modification needed in :file:`setup.py`.
 
-.. todo::
-
-    Link to a "How to modernize a setup.py based project?"
-
 
 Is ``pyproject.toml`` mandatory?
 ================================
@@ -124,10 +120,7 @@ at the root of its source tree with a content like this:
     build-backend = "setuptools.build_meta"
 
 
-.. todo::
-
-    Link to "How to modernize a setup.py based project?"
-
+The guide :ref:`modernize-setup-py-project` has more details about this.
 
 The standard fallback behavior for a :term:`build frontend <Build Frontend>`
 in the absence of a :file:`pyproject.toml` file and its ``[build-system]`` table

source/guides/modernize-setup-py-project.rst

@@ -0,0 +1,249 @@
+.. _modernize-setup-py-project:
+
+
+==============================================
+How to modernize a ``setup.py`` based project?
+==============================================
+
+
+Should ``pyproject.toml`` be added?
+===================================
+
+A :term:`pyproject.toml` file is strongly recommended.
+The presence of a :file:`pyproject.toml` file itself does not bring much. [#]_
+What is actually strongly recommended is the ``[build-system]`` table in :file:`pyproject.toml`.
+
+.. [#] Note that it has influence on the build isolation feature of *pip*,
+    see below.
+
+
+Should ``setup.py`` be deleted?
+===============================
+
+No, :file:`setup.py` can exist in a modern :ref:`setuptools` based project.
+The :term:`setup.py` file is a valid configuration file for setuptools
+that happens to be written in Python.
+However, the following commands are deprecated and **MUST NOT** be run anymore,
+and their recommended replacement commands can be used instead:
+
++---------------------------------+----------------------------------------+
+| Deprecated                      | Current recommendation                 |
++=================================+========================================+
+| ``python setup.py install``     | ``python -m pip install .``            |
++---------------------------------+----------------------------------------+
+| ``python setup.py develop``     | ``python -m pip install --editable .`` |
++---------------------------------+----------------------------------------+
+| ``python setup.py sdist``       | ``python -m build``                    |
++---------------------------------+                                        |
+| ``python setup.py bdist_wheel`` |                                        |
++---------------------------------+----------------------------------------+
+
+
+For more details:
+
+* :ref:`setup-py-deprecated`
+
+
+Where to start?
+===============
+
+The :term:`project` must contain a :file:`pyproject.toml` file at the root of its source tree
+that contains a ``[build-system]`` table like so:
+
+.. code:: toml
+
+    [build-system]
+    requires = ["setuptools"]
+    build-backend = "setuptools.build_meta"
+
+
+This is the standardized method of letting :term:`build frontends <Build Frontend>` know
+that :ref:`setuptools` is the :term:`build backend <Build Backend>` for this project.
+
+Note that the presence of a :file:`pyproject.toml` file (even if empty)
+triggers :ref:`pip` to change its default behavior to use *build isolation*.
+
+For more details:
+
+* :ref:`distributing-packages`
+* :ref:`declaring-build-dependencies`
+* :doc:`pip:reference/build-system/pyproject-toml`
+
+
+How to handle additional build-time dependencies?
+=================================================
+
+On top of setuptools itself,
+if :file:`setup.py` depends on other third-party libraries (outside of Python's standard library),
+those must be listed in the ``requires`` list of the ``[build-system]`` table,
+so that the build frontend knows to install them
+when building the :term:`distributions <Distribution Package>`.
+
+For example, a :file:`setup.py` file such as this:
+
+.. code:: python
+
+    import setuptools
+    import some_build_toolkit  # comes from the `some-build-toolkit` library
+
+    def get_version():
+        version = some_build_toolkit.compute_version()
+        return version
+
+    setuptools.setup(
+        name="my-project",
+        version=get_version(),
+    )
+
+
+requires a :file:`pyproject.toml` file like this (:file:`setup.py` stays unchanged):
+
+.. code:: toml
+
+    [build-system]
+    requires = [
+        "setuptools",
+        "some-build-toolkit",
+    ]
+    build-backend = "setuptools.build_meta"
+
+
+For more details:
+
+* :ref:`declaring-build-dependencies`
+
+
+What is the build isolation feature?
+====================================
+
+Build frontends typically create an ephemeral virtual environment
+where they install only the build dependencies (and their dependencies)
+that are listed under ``build-sytem.requires``
+and trigger the build in that environment.
+
+For some projects this isolation is unwanted and it can be deactivated as follows:
+
+* ``python -m build --no-isolation``
+* ``python -m install --no-build-isolation``
+
+For more details:
+
+* :doc:`pip:reference/build-system/pyproject-toml`
+
+
+How to handle packaging metadata?
+=================================
+
+All static metadata can optionally be moved to a ``[project]`` table in :file:`pyproject.toml`.
+
+For example, a :file:`setup.py` file such as this:
+
+.. code:: python
+
+    import setuptools
+
+    setuptools.setup(
+        name="my-project",
+        version="1.2.3",
+    )
+
+
+can be entirely replaced by a :file:`pyproject.toml` file like this:
+
+.. code:: toml
+
+    [build-system]
+    requires = ["setuptools"]
+    build-backend = "setuptools.build_meta"
+
+    [project]
+    name = "my-project"
+    version = "1.2.3"
+
+
+Read :ref:`declaring-project-metadata` for the full specification
+of the content allowed in the ``[project]`` table.
+
+
+How to handle dynamic metadata?
+===============================
+
+If some packaging metadata fields are not static
+they need to be listed as ``dynamic`` in this ``[project]`` table.
+
+For example, a :file:`setup.py` file such as this:
+
+.. code:: python
+
+    import setuptools
+    import some_build_toolkit
+
+    def get_version():
+        version = some_build_toolkit.compute_version()
+        return version
+
+    setuptools.setup(
+        name="my-project",
+        version=get_version(),
+    )
+
+
+can be modernized as follows:
+
+.. code:: toml
+
+    [build-system]
+    requires = [
+        "setuptools",
+        "some-build-toolkit",
+    ]
+    build-backend = "setuptools.build_meta"
+
+    [project]
+    name = "my-project"
+    dynamic = ["version"]
+
+
+.. code:: python
+
+    import setuptools
+    import some_build_toolkit
+
+    def get_version():
+        version = some_build_toolkit.compute_version()
+        return version
+
+    setuptools.setup(
+        version=get_version(),
+    )
+
+
+For more details:
+
+* :ref:`declaring-project-metadata-dynamic`
+
+
+What if something that can not be changed expects a ``setup.py`` file?
+======================================================================
+
+For example, a process exists that can not be changed easily
+and it needs to execute a command such as ``python setup.py --name``.
+
+It is perfectly fine to leave a :file:`setup.py` file in the project source tree
+even after all its content has been moved to :file:`pyproject.toml`.
+This file can be as minimalistic as this:
+
+.. code:: python
+
+    import setuptools
+
+    setuptools.setup()
+
+
+Where to read more about this?
+==============================
+
+* :ref:`declaring-build-dependencies`
+* :ref:`declaring-project-metadata`
+* :doc:`pip:reference/build-system/pyproject-toml`
+* :doc:`setuptools:build_meta`

source/guides/section-build-and-publish.rst

@@ -15,3 +15,4 @@ Building and Publishing
    using-testpypi
    making-a-pypi-friendly-readme
    publishing-package-distribution-releases-using-github-actions-ci-cd-workflows
+   modernize-setup-py-project

source/specifications/declaring-project-metadata.rst

@@ -379,6 +379,9 @@ metadata.
       "click",
     ]
 
+
+.. _declaring-project-metadata-dynamic:
+
 ``dynamic``
 -----------