django-stubs VS ccache

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?

# Download and install ccache for faster compilation wget https://github.com/ccache/ccache/releases/download/v4.8.3/ccache-4.8.3.tar.xz tar -xf ccache-4.8.3.tar.xz pushd ccache-4.8.3 cmake . make -j $CPUS make install popd # Install NumPy, a dependency for PyTorch dnf install -y numpy # Install Python typing extensions for better type-checking sudo -u ec2-user pip3 install typing-extensions # Clone PyTorch repository and install from source git clone --recursive https://github.com/pytorch/pytorch.git pushd pytorch python3 setup.py install popd # Refresh the dynamic linker run-time bindings ldconfig # Install additional Python libraries for PyTorch sudo -u ec2-user pip3 install sympy filelock fsspec networkx

> What can I use to cache with MSVC that isn't Incredibuild?

Ccache works, but if you use the Visual Studio C++ compiler you need to configure your build to be cacheable.

https://github.com/ccache/ccache/wiki/MS-Visual-Studio

That ecosystem now is too young. All these things must be configured by an automatic installer. Packages and pods need to be tested before release, etc. Previous was 80 min compilation time of the Firestore package. Solved with https://ccache.dev/. But why Dart developers must know, how to install and configure object cache for C++ compilers?

Related

https://github.com/icecc/icecream - another option that does what distcc does, but aimed at a somewhat different use case.

https://ccache.dev/ - a similar idea but provides caching of build outputs instead of distributing builds. You can use it together with distcc to achieve even better performance.

> All those big changes introduce commits that make git bisect generally slower.

Bisection search is log2(n) so doubling the number of commits should only add one more bisection step, yes?

> Which might be awful if you also have some C code to recompile at every step of bisecting.

That reminds me, I've got to try out ccache (https://ccache.dev/ ) for my project. My full compile is one minute, but the three files that take longest to compiler rarely change.

I worked with the internals of this some 16 years ago, maintaining a customized version at Zeugma Systems. Some change of mine was reworked by someone and upstreamed:

https://github.com/ccache/ccache/commit/e8354384f67bc733bea5...