| # Contributing | |
| ## Local development | |
| - The complete test suite depends on having at least the following installed | |
| (possibly not a complete list) | |
| - git (Version 2.24.0 or above is required to run pre-merge-commit tests) | |
| - python2 (Required by a test which checks different python versions) | |
| - python3 (Required by a test which checks different python versions) | |
| - tox (or virtualenv) | |
| - ruby + gem | |
| - docker | |
| - conda | |
| - cargo (required by tests for rust dependencies) | |
| - go (required by tests for go dependencies) | |
| - swift | |
| ### Setting up an environment | |
| This is useful for running specific tests. The easiest way to set this up | |
| is to run: | |
| 1. `tox --devenv venv` (note: requires tox>=3.13) | |
| 2. `. venv/bin/activate` (or follow the [activation instructions] for your | |
| platform) | |
| This will create and put you into a virtualenv which has an editable | |
| installation of pre-commit. Hack away! Running `pre-commit` will reflect | |
| your changes immediately. | |
| ### Running a specific test | |
| Running a specific test with the environment activated is as easy as: | |
| `pytest tests -k test_the_name_of_your_test` | |
| ### Running all the tests | |
| Running all the tests can be done by running `tox -e py37` (or your | |
| interpreter version of choice). These often take a long time and consume | |
| significant cpu while running the slower node / ruby integration tests. | |
| Alternatively, with the environment activated you can run all of the tests | |
| using: | |
| `pytest tests` | |
| ### Setting up the hooks | |
| With the environment activated simply run `pre-commit install`. | |
| ## Documentation | |
| Documentation is hosted at https://pre-commit.com | |
| This website is controlled through | |
| https://github.com/pre-commit/pre-commit.github.io | |
| ## Adding support for a new hook language | |
| pre-commit already supports many [programming languages](https://pre-commit.com/#supported-languages) | |
| to write hook executables with. | |
| When adding support for a language, you must first decide what level of support | |
| to implement. The current implemented languages are at varying levels: | |
| - 0th class - pre-commit does not require any dependencies for these languages | |
| as they're not actually languages (current examples: fail, pygrep) | |
| - 1st class - pre-commit will bootstrap a full interpreter requiring nothing to | |
| be installed globally (current examples: node, ruby) | |
| - 2nd class - pre-commit requires the user to install the language globally but | |
| will install tools in an isolated fashion (current examples: python, go, rust, | |
| swift, docker). | |
| - 3rd class - pre-commit requires the user to install both the tool and the | |
| language globally (current examples: script, system) | |
| "third class" is usually the easiest to implement first and is perfectly | |
| acceptable. | |
| Ideally the language works on the supported platforms for pre-commit (linux, | |
| windows, macos) but it's ok to skip one or more platforms (for example, swift | |
| doesn't run on windows). | |
| When writing your new language, it's often useful to look at other examples in | |
| the `pre_commit/languages` directory. | |
| It might also be useful to look at a recent pull request which added a | |
| language, for example: | |
| - [rust](https://github.com/pre-commit/pre-commit/pull/751) | |
| - [fail](https://github.com/pre-commit/pre-commit/pull/812) | |
| - [swift](https://github.com/pre-commit/pre-commit/pull/467) | |
| ### `language` api | |
| here are the apis that should be implemented for a language | |
| Note that these are also documented in [`pre_commit/languages/all.py`](https://github.com/pre-commit/pre-commit/blob/master/pre_commit/languages/all.py) | |
| #### `ENVIRONMENT_DIR` | |
| a short string which will be used for the prefix of where packages will be | |
| installed. For example, python uses `py_env` and installs a `virtualenv` at | |
| that location. | |
| this will be `None` for 0th / 3rd class languages as they don't have an install | |
| step. | |
| #### `get_default_version` | |
| This is used to retrieve the default `language_version` for a language. If | |
| one cannot be determined, return `'default'`. | |
| You generally don't need to implement this on a first pass and can just use: | |
| ```python | |
| get_default_version = helpers.basic_default_version | |
| ``` | |
| `python` is currently the only language which implements this api | |
| #### `healthy` | |
| This is used to check whether the installed environment is considered healthy. | |
| This function should return `True` or `False`. | |
| You generally don't need to implement this on a first pass and can just use: | |
| ```python | |
| healthy = helpers.basic_healthy | |
| ``` | |
| `python` is currently the only language which implements this api, for python | |
| it is checking whether some common dlls are still available. | |
| #### `install_environment` | |
| this is the trickiest one to implement and where all the smart parts happen. | |
| this api should do the following things | |
| - (0th / 3rd class): `install_environment = helpers.no_install` | |
| - (1st class): install a language runtime into the hook's directory | |
| - (2nd class): install the package at `.` into the `ENVIRONMENT_DIR` | |
| - (2nd class, optional): install packages listed in `additional_dependencies` | |
| into `ENVIRONMENT_DIR` (not a required feature for a first pass) | |
| #### `run_hook` | |
| This is usually the easiest to implement, most of them look the same as the | |
| `node` hook implementation: | |
| https://github.com/pre-commit/pre-commit/blob/160238220f022035c8ef869c9a8642f622c02118/pre_commit/languages/node.py#L72-L74 | |
| [activation instructions]: https://virtualenv.pypa.io/en/latest/user_guide.html#activators | |