django-stubs VS pre-commit

Pyright doesn't work with Django, as Django's so dynamic that it requires a plugin to infer all types correctly. Sadly, even mypy with plugins is a mess to get set up in vscode, especially if you want it to use the same config as you use for ci checks from the command line.

We use mypy + [django-stubs](https://github.com/typeddjango/django-stubs) (in a huge Django + drf project at day job) which includes a plugin for mypy allowing it to recognize all reverse relations and manager methods. Mypy is still really rough around the edges. The cli args are poorly documented, and how they correspond to declarations in a mypy.ini / pyproject.toml is mysterious. Match-statements still have bugs even a year after release. Exclusion of untyped / partially typed files and packages we've had to solve with grep filtering mypy's output for our whitelisted set of files, as it's been unable to separate properly between errors you care about (in your own codebase) and errors in others code (dependencies, untypable dynamic python packages etc).

The largest issue IMO is that mypy tried to adapt a java / OOP style way of type system onto python, instead of recognizing the language's real power within duck typing and passing structural types around. Typescript chose the right approach here, modelling javascript the way it is actually written, favoring structural over nominal typing, instead of the archaic and now left-behind way of Java-style OOP that has influenced mypy.

There was a recently accepted PEP which allowed for limited dataclass transforms, enough to cover the @attr.s usecase for both mypy and pyright, but nowhere near expressive enough to cover django's models and ORM sadly. It's probably impossible / undesirable to allow for such rich plugins, so i see the future for proper pluginless typing to be more akin to how pydantic / normal dataclasses solve typing, by starting with a specification of the types, deriving its runtime implementation, instead of plugins having to reverse the type representation of a custom DSL.

You can annotate the manager and get some typing help in the editor. And there’s django-stubs which helps a little when running mypy. It’s not as good as pycharm though.

https://github.com/typeddjango/django-stubs/tree/master

> Yes, there are type stubs for these libraries but they’re either forced to be more strict, preventing use of dynamism, or opt for being less strict but allowing you to use all the library features, at the cost of safety.

There are type stubs for Django that somewhat avoid these compromises: https://github.com/typeddjango/django-stubs

To be able to do this they have to use a Mypy plugin though. And even then it's still far from perfect.

Mypy together with this plug-in gives you typing for django. https://github.com/TypedDjango/django-stubs

Have you looked at stubs for Django?

Today we are going to look at how to setup Black (a python code formatter) and pre-commit (a package for handling git hooks in python) to automatically format you code on commit.

# See https://pre-commit.com for more information # See https://pre-commit.com/hooks.html for more hooks repos: - repo: https://github.com/pre-commit/pre-commit-hooks rev: v3.2.0 hooks: - id: trailing-whitespace - id: end-of-file-fixer - id: check-yaml - id: check-toml - id: check-added-large-files - repo: local hooks: - id: tox lint name: tox-validation entry: pdm run tox -e test,lint language: system files: ^src\/.+py$|pyproject.toml|^tests\/.+py$ types_or: [python, toml] pass_filenames: false - id: tox docs name: tox-docs language: system entry: pdm run tox -e docs types_or: [python, rst, toml] files: ^src\/.+py$|pyproject.toml|^docs\/ pass_filenames: false - repo: https://github.com/pdm-project/pdm rev: 2.10.4 # a PDM release exposing the hook hooks: - id: pdm-lock-check - repo: https://github.com/jumanjihouse/pre-commit-hooks rev: 3.0.0 hooks: - id: markdownlint

Pre-commit hooks act as the first line of defense in maintaining code quality, seamlessly integrating with linters and code formatters. They automatically execute these tools each time a developer tries to commit code to the repository, ensuring the code adheres to the project's standards. If the hooks detect issues, the commit is paused until the issues are resolved, guaranteeing that only code meeting quality standards makes it into the repository.

Pre-commit Hooks: Pre-commit is a tool that can be set up to enforce coding rules and standards before you commit your changes to your code repository. This ensures that you can't even check in (commit) code that doesn't meet your standards. This allows a code reviewer to focus on the architecture of a change while not wasting time with trivial style nitpicks.

Ah, fair enough!

On my team we use pre-commit[0] a lot. I guess I would define the history to be something like "has this commit ever been run through our pre-commit hooks?". If you rewrite history, you'll (usually) produce commits that have not been through pre-commit (and they've therefore dodged a lot of static checks that might catch code that wasn't working, at that point in time). That gives some manner of objectivity to the "history", although it does depend on each user having their pre-commit hooks activated in their local workspace.

[0]: https://pre-commit.com/

Pre-commit is a framework for managing and maintaining multi-language pre-commit hooks. It supports hooks for various programming languages. Using this framework, you only have to specify a list of hooks you want to run before every commit, and pre-commit handles the installation and execution of those hooks despite your project’s primary language.

You can learn more here: pre-commit.com

Note this includes support for pre-commit.

As a nice next step, you could also add mypy to check your type hints are consistent, and automate running all this via pre-commit hooks set up with… pre-commit.