Metals VS pytype

Links: - https://dotty.epfl.ch/ - https://scala-native.org/en/stable/ - https://www.scala-js.org/ - https://typelevel.org/ - https://zio.dev/ - https://github.com/scala-native/scala-native/pull/3120 - https://github.com/lampepfl/dotty/pull/16517 - https://dotty.epfl.ch/docs/reference/experimental/index.html - https://scala-cli.virtuslab.org/ - https://scalameta.org/metals/ - https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html - https://www.scala-lang.org/blog/2023/04/18/faster-scalajs-development-with-frontend-tooling.html - https://www.scala-lang.org/blog/2022/08/17/long-term-compatibility-plans.html

You might want to look at Scala, they have proper LSP support with metals which means you can write your code in vscode, neovim, emacs, or even fleet (the new jetbrains text editor).

Please write in the comments if you know of any language servers I should test it with. Currently I tested only metals and rust-analyzer.

If you are using nvim-lspconfig you can pass the settings as a Lua table to the setup function. For example, here are may metals settings:

Bazel support in Metals. I didn't spend all that time figuring out and adjusting Emacs/Spacemacs and making my workflow (almost) mouse-free just to scrap my config and switch to IDEA's rodent infested ways.

There is one small issue involving code completion returning inappropriate completions in some cases; https://github.com/scalameta/metals/pull/4414 will fix it, once it's included in a release. Perhaps that's the PR you saw?

It is, by quite a bit.

While the "Scala IDE" project is dead for all practical purposes, IntelliJ IDEA's Scala plugin is actually pretty amazing. There's also a VisualStudio plugin that does pretty much the same and is advancing by leaps and bounds. There are also interconnecting projects that provide i.e. language server or build server that are reused by other projects. It's pretty modular. Metals (https://scalameta.org/metals/) is amazing.

In general the language has become a wee bit faster to build, there was good progress with build times during the 2.12/2.13 cycles.

With Scala3 the language got a bit simpler; concepts that were implemented explicitly using (hehe) implicits got their own keywords and a lot of the opinionated boilercode that cause a lot of debates is now generated during complication and hidden. A lot of "standardization" has occurred.

IntelliJ has its own BSP. The other one is Metals. You can use it with many IDEs (vim, emacs, vscode, atom,...). Use it with emacs if you're comfortable with it.

it's open source! check out https://github.com/google/pytype and https://github.com/google/pytype/blob/main/docs/developers/t... for more on the multi-file runner

Pytype checks and infers types for your Python code - without requiring type annotations. Pytype can catch type errors in your Python code before you even run it.

Pyre from Meta, pyright from Microsoft and PyType from Google provide additional assistance. They can 'infer' types based on code flow and existing types within the code.

we've written a little bit about what pytype does differently here: https://google.github.io/pytype/

our main focus is to be able to work with unannotated and partially-annotated code, and treat it on par with fully annotated code.

So, I tried out pytype the other day, and it was a not a good experience. It doesn't support PEP 420 (implicit namespace packages), which means you have to litter __init__.py files everywhere, or it will create filename collisions. See https://github.com/google/pytype/issues/198 for more information. I've since started testing out pyre.

What is the smart money doing for type checking in Python? I've used mypy which seems to work well but is incredibly slow (3-4s to update linting after I change code). I've tried pylance type checking in VS Code, which seems to work well + fast but is less clear and comprehensive than mypy. I've also seen projects like pytype [1] and pyre [2] used by Google/Meta, but people say those tools don't really make sense to use unless you're an engineer for those companies.

Am just curious if mypy is really the best option right now?

[1] https://github.com/google/pytype

At Luma, we're using mypy to check nearly our entire code-base, including our Maya-related code, thanks to these latest changes. Fully adopting mypy (or an alternative like pytype) is no small feat, but working within a fully type-annotated code base with a type checker to enforce accuracy is like coding in a higher plane of existence: fewer bugs, easier code navigation, faster dev onboarding, easier refactoring, and dramatically increased confidence about every change. I wrote about some deeper insights in these posts.

Check out https://github.com/google/pytype

i work on https://github.com/google/pytype which is largely developed internally and then pushed to github every few days. the github commits are associated with the team's personal github accounts. pytype is not an "official google product" insofar as the open source version is presented as is without official google support, but it is "production code" in the sense that it is very much used extensively within google.

pytype dev here - thanks for the kind words :) whole-program analysis on unannotated or partially-annotated code is our particular focus, but there's surprisingly little dark PLT magic involved; in particular you don't need to be an academic type theory wizard to understand how it works. our developer docs[1] have more info, but at a high level we have an interpreter that virtually executes python bytecode, tracking types where the cpython interpreter would have tracked values.

it's worth exploring some of the other type checkers as well, since they make different tradeoffs - in particular, microsoft's pyright[2] (written in typescript!) can run incrementally within vscode, and tends to add new and experimentally proposed typing PEPs faster than we do.

[1] https://github.com/google/pytype/blob/main/docs/developers/i...