python: add devel package requirements to setuptools

setuptools doesn't have a formal understanding of development requires,
but it has an optional feataures section. Fine; add a "devel" feature
and add the requirements to it.

To avoid duplication, we can modify pipenv to install qemu[devel]
instead. This enables us to run invocations like "pip install -e
.[devel]" and test the package on bleeding-edge packages beyond those
specified in Pipfile.lock.

Importantly, this also allows us to install the qemu development
packages in a non-networked mode: `pip3 install --no-index -e .[devel]`
will now fail if the proper development dependencies are not already
met. This can be useful for automated build scripts where fetching
network packages may be undesirable.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
Message-id: 20210527211715.394144-27-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

python/PACKAGE.rst

@@ -31,3 +31,7 @@ official `GitLab mirror <https://gitlab.com/qemu-project/qemu>`_.
 Please report bugs on the `QEMU issue tracker
 <https://gitlab.com/qemu-project/qemu/-/issues>`_ and tag ``@jsnow`` in
 the report.
+
+Optional packages necessary for running code quality analysis for this
+package can be installed with the optional dependency group "devel":
+``pip install qemu[devel]``.

python/Pipfile

@@ -4,10 +4,7 @@ url = "https://pypi.org/simple"
 verify_ssl = true
 
 [dev-packages]
-flake8 = ">=3.6.0"
-isort = ">=5.1.2"
-mypy = ">=0.770"
-pylint = ">=2.8.0"
+qemu = {editable = true, extras = ["devel"], path = "."}
 
 [packages]
 qemu = {editable = true,path = "."}

python/README.rst

@@ -24,6 +24,10 @@ which installs a version of the package that installs a forwarder
 pointing to these files, such that the package always reflects the
 latest version in your git tree.
 
+Installing ".[devel]" instead of "." will additionally pull in required
+packages for testing this package. They are not runtime requirements,
+and are not needed to simply use these libraries.
+
 See `Installing packages using pip and virtual environments
 <https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/>`_
 for more information.

python/setup.cfg

@@ -22,6 +22,15 @@ packages =
     qemu.machine
     qemu.utils
 
+[options.extras_require]
+# Run `pipenv lock --dev` when changing these requirements.
+devel =
+    flake8 >= 3.6.0
+    isort >= 5.1.2
+    mypy >= 0.770
+    pylint >= 2.8.0
+
+
 [flake8]
 extend-ignore = E722  # Prefer pylint's bare-except checks to flake8's
 exclude = __pycache__,