pw_presubmit¶

The presubmit module provides Python tools for running presubmit checks and checking and fixing code format. It also includes the presubmit check script for the Pigweed repository, pigweed_presubmit.py.

Presubmit checks are essential tools, but they take work to set up, and projects don’t always get around to it. The pw_presubmit module provides tools for setting up high quality presubmit checks for any project. We use this framework to run Pigweed’s presubmit on our workstations and in our automated building tools.

The pw_presubmit module also includes pw format, a tool that provides a unified interface for automatically formatting code in a variety of languages. With pw format, you can format C, C++, Python, GN, and Go code according to configurations defined by your project. pw format leverages existing tools like clang-format, and it’s simple to add support for new languages.

The pw_presubmit package includes presubmit checks that can be used with any project. These checks include:

Check code format of several languages including C, C++, and Python
Initialize a Python environment
Run all Python tests
Run pylint
Run mypy
Ensure source files are included in the GN and Bazel builds
Build and run all tests with GN
Build and run all tests with Bazel
Ensure all header files contain #pragma once

Compatibility¶

Python 3

Creating a presubmit check for your project¶

Creating a presubmit check for a project using pw_presubmit is simple, but requires some customization. Projects must define their own presubmit check Python script that uses the pw_presubmit package.

A project’s presubmit script can be registered as a pw_cli plugin, so that it can be run as pw presubmit.

Setting up the command-line interface¶

The pw_presubmit.cli module sets up the command-line interface for a presubmit script. This defines a standard set of arguments for invoking presubmit checks. Its use is optional, but recommended.

pw_presubmit.cli¶

Argument parsing code for presubmit checks.

pw_presubmit.cli.add_arguments(parser: argparse.ArgumentParser, programs: Optional[pw_presubmit.presubmit.Programs] = None, default: str = '') → None¶: Adds common presubmit check options to an argument parser.

pw_presubmit.cli.run(program: Sequence[Callable], output_directory: Optional[pathlib.Path], package_root: pathlib.Path, clear: bool, root: pathlib.Path = None, repositories: Collection[pathlib.Path] = (), only_list_steps=False, **other_args) → int¶

Processes arguments from add_arguments and runs the presubmit.

Parameters

program – from the –program option
output_directory – from –output-directory option
package_root – from –package-root option
clear – from the –clear option
root – base path from which to run presubmit checks; defaults to the root of the current directory’s repository
repositories – roots of Git repositories on which to run presubmit checks; defaults to the root of the current directory’s repository
only_list_steps – list the steps that would be executed, one per line, instead of executing them
**other_args – remaining arguments defined by by add_arguments

Returns

exit code for sys.exit; 0 if succesful, 1 if an error occurred

Presubmit checks¶

A presubmit check is defined as a function or other callable. The function must accept one argument: a PresubmitContext, which provides the paths on which to run. Presubmit checks communicate failure by raising an exception.

Presubmit checks may use the filter_paths decorator to automatically filter the paths list for file types they care about.

Either of these functions could be used as presubmit checks:

@pw_presubmit.filter_paths(endswith='.py')
def file_contains_ni(ctx: PresubmitContext):
    for path in ctx.paths:
        with open(path) as file:
            contents = file.read()
            if 'ni' not in contents and 'nee' not in contents:
                raise PresumitFailure('Files must say "ni"!', path=path)

def run_the_build(_):
    subprocess.run(['make', 'release'], check=True)

Presubmit checks functions are grouped into “programs” – a named series of checks. Projects may find it helpful to have programs for different purposes, such as a quick program for local use and a full program for automated use. The example script uses pw_presubmit.Programs to define quick and full programs.

pw_presubmit¶

The pw_presubmit package provides tools for running presubmit checks.

pw_presubmit.filter_paths(endswith: Iterable[str] = '', exclude: Iterable[Union[Pattern[str], str]] = (), always_run: bool = False) → Callable[[Callable], pw_presubmit.presubmit._Check]¶

Decorator for filtering the paths list for a presubmit check function.

Path filters only apply when the function is used as a presubmit check. Filters are ignored when the functions are called directly. This makes it possible to reuse functions wrapped in @filter_paths in other presubmit checks, potentially with different path filtering rules.

Parameters

endswith – str or iterable of path endings to include
exclude – regular expressions of paths to exclude

Returns

a wrapped version of the presubmit function

pw_presubmit.call(*args, **kwargs) → None¶: Optional subprocess wrapper that causes a PresubmitFailure on errors.

exception pw_presubmit.PresubmitFailure(description: str = '', path=None)¶: Optional exception to use for presubmit failures.

class pw_presubmit.Programs(**programs: Sequence)¶

A mapping of presubmit check programs.

Use is optional. Helpful when managing multiple presubmit check programs.

Example¶

A simple example presubmit check script follows. This can be copied-and-pasted to serve as a starting point for a project’s presubmit check script.

See pigweed_presubmit.py for a more complex presubmit check script example.

"""Example presubmit check script."""

import argparse
import logging
import os
from pathlib import Path
import re
import sys
from typing import List, Pattern

try:
    import pw_cli.log
except ImportError:
    print('ERROR: Activate the environment before running presubmits!',
          file=sys.stderr)
    sys.exit(2)

import pw_presubmit
from pw_presubmit import build, cli, environment, format_code, git_repo
from pw_presubmit import python_checks, filter_paths, PresubmitContext
from pw_presubmit.install_hook import install_hook

# Set up variables for key project paths.
PROJECT_ROOT = Path(os.environ['MY_PROJECT_ROOT'])
PIGWEED_ROOT = PROJECT_ROOT / 'pigweed'

#
# Initialization
#
def init_cipd(ctx: PresubmitContext):
    environment.init_cipd(PIGWEED_ROOT, ctx.output_dir)


def init_virtualenv(ctx: PresubmitContext):
    environment.init_virtualenv(PIGWEED_ROOT,
                                ctx.output_dir,
                                setup_py_roots=[PROJECT_ROOT])


# Rerun the build if files with these extensions change.
_BUILD_EXTENSIONS = frozenset(
    ['.rst', '.gn', '.gni', *format_code.C_FORMAT.extensions])


#
# Presubmit checks
#
def release_build(ctx: PresubmitContext):
    build.gn_gen(PROJECT_ROOT, ctx.output_dir, build_type='release')
    build.ninja(ctx.output_dir)


def host_tests(ctx: PresubmitContext):
    build.gn_gen(PROJECT_ROOT, ctx.output_dir, run_host_tests='true')
    build.ninja(ctx.output_dir)


# Avoid running some checks on certain paths.
PATH_EXCLUSIONS = (
    re.compile(r'^external/'),
    re.compile(r'^vendor/'),
)


# Use the upstream pragma_once check, but apply a different set of path
# filters with @filter_paths.
@filter_paths(endswith='.h', exclude=PATH_EXCLUSIONS)
def pragma_once(ctx: PresubmitContext):
    pw_presubmit.pragma_once(ctx)


#
# Presubmit check programs
#
QUICK = (
    # Initialize an environment for running presubmit checks.
    init_cipd,
    init_virtualenv,
    # List some presubmit checks to run
    pragma_once,
    host_tests,
    # Use the upstream formatting checks, with custom path filters applied.
    format_code.presubmit_checks(exclude=PATH_EXCLUSIONS),
)

FULL = (
    QUICK,  # Add all checks from the 'quick' program
    release_build,
    # Use the upstream Python checks, with custom path filters applied.
    python_checks.all_checks(exclude=PATH_EXCLUSIONS),
)

PROGRAMS = pw_presubmit.Programs(quick=QUICK, full=FULL)


def run(install: bool, **presubmit_args) -> int:
    """Process the --install argument then invoke pw_presubmit."""

    # Install the presubmit Git pre-push hook, if requested.
    if install:
        install_hook(__file__, 'pre-push', ['--base', 'HEAD~'],
                     git_repo.root())
        return 0

    return cli.run(root=PROJECT_ROOT, **presubmit_args)


def main() -> int:
    """Run the presubmit checks for this repository."""
    parser = argparse.ArgumentParser(description=__doc__)
    cli.add_arguments(parser, PROGRAMS, 'quick')

    # Define an option for installing a Git pre-push hook for this script.
    parser.add_argument(
        '--install',
        action='store_true',
        help='Install the presubmit as a Git pre-push hook and exit.')

    return run(**vars(parser.parse_args()))

if __name__ == '__main__':
    pw_cli.log.install(logging.INFO)
    sys.exit(main())

Code formatting tools¶

The pw_presubmit.format_code module formats supported source files using external code format tools. The file format_code.py can be invoked directly from the command line or from pw as pw format.