cpython/Doc/packaging/commandhooks.rst

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.. TODO integrate this in commandref and configfile
.. _packaging-command-hooks:
=============
Command hooks
=============
Packaging provides a way of extending its commands by the use of pre- and
post-command hooks. Hooks are Python functions (or any callable object) that
take a command object as argument. They're specified in :ref:`config files
<packaging-config-filenames>` using their fully qualified names. After a
command is finalized (its options are processed), the pre-command hooks are
executed, then the command itself is run, and finally the post-command hooks are
executed.
See also global setup hooks in :ref:`setupcfg-spec`.
.. _packaging-finding-hooks:
Finding hooks
=============
As a hook is configured with a Python dotted name, it must either be defined in
a module installed on the system, or in a module present in the project
directory, where the :file:`setup.cfg` file lives::
# file: _setuphooks.py
def hook(install_cmd):
metadata = install_cmd.dist.metadata
print('Hooked while installing %r %s!' % (metadata['Name'],
metadata['Version']))
Then you need to configure it in :file:`setup.cfg`::
[install_dist]
pre-hook.a = _setuphooks.hook
Packaging will add the project directory to :data:`sys.path` and find the
``_setuphooks`` module.
Hooks defined in different config files (system-wide, user-wide and
project-wide) do not override each other as long as they are specified with
different aliases (additional names after the dot). The alias in the example
above is ``a``.