pbr - Python Build Reasonableness

A library for managing setuptools packaging needs in a consistent manner.

pbr reads and then filters the setup.cfg data through a setup hook to fill in default values and provide more sensible behaviors, and then feeds the results in as the arguments to a call to setup.py - so the heavy lifting of handling python packaging needs is still being done by setuptools.

What It Does

PBR can and does do a bunch of things for you:

  • Version: Manage version number based on git revisions and tags
  • AUTHORS: Generate AUTHORS file from git log
  • ChangeLog: Generate ChangeLog from git log
  • Sphinx Autodoc: Generate autodoc stub files for your whole module
  • Requirements: Store your dependencies in a pip requirements file
  • long_description: Use your README file as a long_description
  • Smart find_packages: Smartly find packages under your root package

Version

Versions can be managed two ways - postversioning and preversioning. Postversioning is the default, and preversioning is enabeld by setting version in the setup.cfg metadata section. In both cases version strings are inferred from git.

If a given revision is tagged, that’s the version.

If it’s not, then we take the last tagged version number and increment it to get a minimum target version.

If postversioning is in use, we use the resulting version number as the target version.

If preversioning is in use - that is if there is a version set in setup.cfg metadata - then we check that that version is higher than the target version we inferred above. If it is not, we raise an error, otherwise we use the version from setup.cfg as the target.

We then generate dev version strings based on the commits since the last release and include the current git sha to disambiguate multiple dev versions with the same number of commits since the release.

Note

Note that pbr expects git tags to be signed, for using it to calculate version.

The versions are expected to be compliant with Linux Compatible Semantic Versioning 3.0.0.

The version.SemanticVersion class can be used to query versions of a package and present it in various forms - debian_version(), release_string(), rpm_string(), version_string(), or version_tuple().

AUTHORS and ChangeLog

Why keep an AUTHORS or a ChangeLog file, when git already has all of the information you need. AUTHORS generation supports filtering/combining based on a standard .mailmap file.

Sphinx Autodoc

Sphinx can produce auto documentation indexes based on signatures and docstrings of your project- but you have to give it index files to tell it to autodoc each module. That’s kind of repetitive and boring. PBR will scan your project, find all of your modules, and generate all of the stub files for you.

Sphinx documentation setups are altered to generate man pages by default. They also have several pieces of information that are known to setup.py injected into the sphinx config.

Requirements

You may not have noticed, but there are differences in how pip requirements.txt files work and how distutils wants to be told about requirements. The pip way is nicer, because it sure does make it easier to populate a virtualenv for testing, or to just install everything you need. Duplicating the information, though, is super lame. So PBR will let you keep requirements.txt format files around describing the requirements for your project, will parse them and split them up appropriately, and inject them into the install_requires and/or tests_require and/or dependency_links arguments to setup. Voila!

You can also have a requirement file for each specific major version of Python. If you want to have a different package list for Python 3, just drop a requirements-py3.txt, and it will be used instead.

The requirement files are tried in that order (N being the Python major version number used to install the package):

  • requirements-pyN.txt
  • tools/pip-requires-py3
  • requirements.txt
  • tools/pip-requires

Only the first file found is used to install the list of packages it contains.

long_description

There is no need to maintain two long descriptions- and your README file is probably a good long_description. So we’ll just inject the contents of your README.rst, README.txt or README file into your empty long_description. Yay for you.

Usage

pbr requires a distribution to use distribute. Your distribution must include a distutils2-like setup.cfg file, and a minimal setup.py script.

A simple sample can be found in pbr’s own setup.cfg (it uses its own machinery to install itself):

[metadata]
name = pbr
author = OpenStack Foundation
author-email = openstack-dev@lists.openstack.org
summary = OpenStack's setup automation in a reusable form
description-file = README
license = Apache-2
classifier =
    Development Status :: 4 - Beta
        Environment :: Console
        Environment :: OpenStack
        Intended Audience :: Developers
        Intended Audience :: Information Technology
        License :: OSI Approved :: Apache Software License
        Operating System :: OS Independent
        Programming Language :: Python
keywords =
    setup
    distutils
[files]
packages =
    pbr
data_files =
    etc/pbr = etc/*
    etc/init =
        pbr.packaging.conf
        pbr.version.conf
[entry_points]
console_scripts =
    pbr = pbr.cmd:main
pbr.config.drivers =
    plain = pbr.cfg.driver:Plain

The minimal setup.py should look something like this:

#!/usr/bin/env python

from setuptools import setup

setup(
    setup_requires=['pbr'],
    pbr=True,
)

Note that it’s important to specify pbr=True or else the pbr functionality will not be enabled.

It should also work fine if additional arguments are passed to setup(), but it should be noted that they will be clobbered by any options in the setup.cfg file.

files

The format of the files section is worth explaining. There are three fundamental keys one is likely to care about, packages, namespace_packages, and data_files.

packages is a list of top-level packages that should be installed. The behavior of packages is similar to setuptools.find_packages in that it recurses the python package hierarchy below the given top level and installs all of it. If packages is not specified, it defaults to the name given in the [metadata] section.

namespace_packages is the same, but is a list of packages that provide namespace packages.

data_files lists files to be installed. The format is an indented block that contains key value pairs which specify target directory and source file to install there. More than one source file for a directory may be indicated with a further indented list. Source files are stripped of leading directories. Additionally, pbr supports a simple file globbing syntax for installing entire directory structures, so:

[files]
data_files =
    etc/pbr = etc/pbr/*
    etc/neutron =
        etc/api-paste.ini
        etc/dhcp-agent.ini
    etc/init.d = neutron.init

Will result in /etc/neutron containing api-paste.ini and dhcp-agent.ini, both of which pbr will expect to find in the etc directory in the root of the source tree. Additionally, neutron.init from that dir will be installed in /etc/init.d.

All of the files and directories located under etc/pbr in the source tree will be installed into /etc/pbr.

entry_points

The general syntax of specifying entry points is a top level name indicating the entry point group name, followed by one or more key value pairs naming the entry point to be installed. For instance:

[entry_points]
console_scripts =
    pbr = pbr.cmd:main
pbr.config.drivers =
    plain = pbr.cfg.driver:Plain
    fancy = pbr.cfg.driver:Fancy

Will cause a console script called pbr to be installed that executes the main function found in pbr.cmd. Additionally, two entry points will be installed for pbr.config.drivers, one called plain which maps to the Plain class in pbr.cfg.driver and one called fancy which maps to the Fancy class in pbr.cfg.driver.

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