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Description:

pazel 0.1.0

pazel - generate Bazel BUILD files for Python

Requirements
pazel
No requirements. Tested on Python 2.7 and 3.6 on Ubuntu 16.04 and macOS High Sierra.
Bazel
Tested on Bazel 0.11.1. All recent versions are expected to work.
Installation
> git clone https://github.com/tuomasr/pazel.git
> cd pazel
> python setup.py install

Usage
NOTE: pazel overwrites any existing BUILD files. Please use version control or have backups of
your current BUILD files before using pazel.
Default usage with Bazel
The following example generates all BUILD files for the sample Python project in sample_app.
Start from the pazel root directory to which the repository was cloned.
> bazel run //pazel:app -- <pazel_root_dir>/sample_app -r <pazel_root_dir>/sample_app
-c <pazel_root_dir>/sample_app/.pazelrc
Generated BUILD files for <pazel_root_dir>/sample_app.

Default usage without Bazel
Start from the pazel root directory.
> cd sample_app
> pazel
Generated BUILD files for <pazel_install_dir>/sample_app.

Testing the generated BUILD files
Now, we can build, test, and run the sample project by running the following invocations in the
sample_app directory, respectively.
> bazel build
> bazel test ...
> bazel run foo:bar3

Command-line options
pazel -h shows a summary of the command-line options. Each of them is explained below.
By default, BUILD files are generated recursively for the current working directory.
Use pazel <some_path> to generate BUILD file(s) recursively for another directory
or for a single Python file.
All imports are assumed to be relative to the current working directory. For example,
sample_app/foo/bar2.py imports from sample_app/foo/bar1.py using from foo.bar1 import sample.
Use pazel -r <some_path> to override the path to which the imports are relative.
By default, pazel adds rules to install all external Python packages. If your environment has
pre-installed packages for which these rules are not required, then use pazel -p.
pazel config file .pazelrc is read from the current working directory. Use
pazel -c <pazelrc_path> to specify an alternative path.
Ignoring rules in existing BUILD files
The tag # pazel-ignore causes pazel to ignore the rule that immediately follows the tag in an
existing BUILD file. In particular, the tag can be used to skip custom rules that pazel does not
handle. pazel places the ignored rules at the bottom of the BUILD file. See sample_app/foo/BUILD
for an example using the tag.
Customizing and extending pazel
pazel can be programmed using a .pazelrc Python file, which is read from the current
working directory or provided explicitly with pazel -c <pazelrc_path>.
The user can define variables HEADER and FOOTER to add custom header and footer to
all BUILD files, respectively. See sample_app/.pazelrc and sample_app/BUILD for an example that
adds the same visibility to all BUILD files.
If some pip package has different install name than import name, then the user
should define EXTRA_IMPORT_NAME_TO_PIP_NAME dictionary accordingly. sample_app/.pazelrc has
{'yaml': 'pyyaml'} as an example. In addition, the user can specify local packages and their
corresponding Bazel dependencies using the EXTRA_LOCAL_IMPORT_NAME_TO_DEP dictionary.
The user can add support for custom Bazel rules by defining a new class implementing the BazelRule
interface in pazel/bazel_rules.py and by adding that class to EXTRA_BAZEL_RULES list in
.pazelrc. sample_app/.pazelrc defines a custom PyDoctestRule class that identifies all
doctests and generates custom py_doctest Bazel rules for them as defined in
sample_app/custom_rules.bzl.
In addition, the user can implement custom rules for mapping Python imports to Bazel dependencies
that are not natively supported. That is achieved by defining a new class implementing the
InferenceImportRule interface in pazel/import_inference_rules.py and by adding the class to
EXTRA_IMPORT_INFERENCE_RULES list in .pazelrc. sample_app/.pazelrc defines a custom
LocalImportAllInferenceRule class that generates the correct Bazel dependencies for
from X import * type of imports where X is a local package.
BUILD file formatting
pazel generates BUILD files that are nearly compatible with
Buildifier. Buildifier can be
applied on pazel-generated BUILD files to remove the remaining differences, if needed.