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Development documentation

This documentation provides guidance on developer workflows for working with the code in this repository.

Table of Contents:

Development Environment Setup

To develop the Python code in this repository you will need:

  1. Python 3.9 or higher. We recommend mise if you would like to run more than one version of Python on the same system. When running unit tests against all supported Python versions, for instance.
  2. The hatch package installed (pip install --upgrade hatch) into your Python environment.

You can develop on a Linux, MacOs, or Windows workstation, but you will find that some of the support scripting is specific to Linux workstations.

The Development Loop

We have configured hatch commands to support a standard development loop. You can run the following from any directory of this repository:

  • hatch build - To build the installable Python wheel and sdist packages into the dist/ directory.
  • hatch run test - To run the PyTest unit tests found in the test/ directory. See Testing.
  • hatch run all:test - To run the PyTest unit tests against all available supported versions of Python.
  • hatch run lint - To check that the package's formatting adheres to our standards.
  • hatch run fmt - To automatically reformat all code to adhere to our formatting standards.
  • hatch shell - Enter a shell environment where you can run the deadline command-line directly as it is implemented in your checked-out local git repository.
  • hatch env prune - Delete all of your isolated workspace environments for this package.

If you are not sure about how to approach development for this package, then we have some suggestions.

  1. Run python within a hatch shell environment for interactive development. Python will import your in-development codebase when you import openjd.cli from this environment. This makes it easy to use interactive python, the python debugger, and short test scripts to develop and test your changes.
    • Note that if you make changes to your source and are running interactive Python then you will need to use importlib.reload to reload the the module(s) that you modified for your modifications to take effect.
  2. Run the test suite frequently (See Testing), and modify/add to it as you are developing your change, rather than only when your change is complete. The test suite runs very quickly, and this will help surface regressions that your change may cause before you get too far into your implementation.

Once you are satisfied with your code, and all relevant tests pass, then run hatch run fmt to fix up the formatting of your code and post your pull request.

Note: Hatch uses environments to isolate the Python development workspace for this package from your system or virtual environment Python. If your build/test run is not making sense, then sometimes pruning (hatch env prune) all of these environments for the package can fix the issue.

Testing

The objective for the tests of this package are to act as regression tests to help identify unintended changes to functionality in the package. As such, we strive to have high test coverage of the different behaviours/functionality that the package contains. Code coverage metrics are not the goal, but rather are a guide to help identify places where there may be gaps in testing coverage.

All tests are all located under the test/ directory of this repository. If you are adding or modifying functionality, then you will almost always want to be writing one or more tests to demonstrate that your logic behaves as expected and that future changes do not accidentally break your change.

Writing Tests

If you want assistance developing tests, then please don't hesitate to open a draft pull request and ask for help. We'll do our best to help you out and point you in the right direction. We also suggest looking at the existing tests for the same or similar functions for inspiration (search for calls to the function within the test/ subdirectories). You will also find both the official PyTest documentation and unitest.mock documentation very informative (we do).

Our tests are implemented using the PyTest testing framework, and tests make use of Python's unittest.mock package to avoid runtime dependencies and narrowly focus tests on a specific aspect of the implementation.

Though our tests make a lot of use of unittest.mock now, our goal is to decrease the usage of mocks to a bare minimum over time. Using a mock inherrently encodes assumptions into the tests about how the mocked functionality functions. So, if a change is made that violates those assumptions then the test suite will not catch it, and we may end up releasing broken code.

Running Tests

You can run tests with:

  • hatch run test - To run the tests with your default Python runtime.
  • hatch run all:test - To run the tests with all of the supported Python runtime versions that you have installed.

Any arguments that you add to these commands are passed through to PyTest. So, if you want to, say, run the Python debugger to investigate a test failure then you can run: hatch run test --pdb

Super verbose test output

If you find that you need much more information from a failing test (say you're debugging a deadlocking test) then a way to get verbose output from the test is to enable Pytest Live Logging:

  1. Add a pytest.ini to the root directory of the repository that contains (Note: for some reason, setting log_cli and log_cli_level in pyproject.toml does not work for us, nor does setting the options on the command-line; if you figure out how to get it to work then please update this section):
[pytest]
xfail_strict = False
log_cli = true
log_cli_level = 10
  1. Modify pyproject.toml to set the following additional addopts in the tool.pytest.ini_options section:
    "-vvvvv",
    "--numprocesses=1"
  1. Add logging statements to your tests as desired and run the test(s) that you are debugging.

Things to Know

The Package's Public Interface

This package is an application wherein we are explicit and intentional with what we expose as public. The command-line interface is, obviously, public as that is the purpose of the application. There are no public Python interfaces; this package is not intended to be used as a library.

The standard convention in Python is to prefix things with an underscore character ('_') to signify that the thing is private to the implementation, and is not intended to be used by external consumers of the thing.

We use this convention in this package in two ways:

  1. In filenames.
    1. Any file whose name is not prefixed with an underscore is a part of the public interface of this package. The name may not change and public symbols (classes, modules, functions, etc.) defined in the file may not be moved to other files or renamed without a major version number change.
    2. Any file whose name is prefixed with an underscore is an internal module of the package and is not part of the public interface. These files can be renamed, refactored, have symbols renamed, etc. Any symbol defined in one of these files that is intended to be part of this package's public interface must be imported into an appropriate __init__.py file.
  2. Every symbol that is defined or imported in a public module and is not intended to be part of the module's public interface is prefixed with an underscore.

For example, a public module in this package will be defined with the following style:

# The os module is not part of this file's external interface
import os as _os

# PublicClass is part of this file's external interface.
class PublicClass:
    def publicmethod(self):
        pass

    def _privatemethod(self):
        pass

# _PrivateClass is not part of this file's external interface.
class _PrivateClass:
    def publicmethod(self):
        pass

    def _privatemethod(self):
        pass

On import os as _os

Every module/symbol that is imported into a Python module becomes a part of that module's interface. Thus, if we have a module called foo.py such as:

# foo.py

import os

Then, the os module becomes part of the public interface for foo.py and a consumer of that module is free to do:

from foo import os

We don't want all (generally, we don't want any) of our imports to become part of the public API for the module, so we import modules/symbols into a public module with the following style:

import os as _os
from typing import Dict as _Dict