Pyrefly: A new type checker and IDE experience for Python

#1

Post by homarp » Sat, May 17, 2025, 12:47 PM UTC

Pyrefly: A new type checker and IDE experience for Python
engineering.fb.com

Re: Pyrefly: A new type checker and IDE experience for Python

#2

Post by homarp » Sat, May 17, 2025, 12:52 PM UTC

this is the official announcement, but pyrefly was previously discuted a few weeks ago: https://news.ycombinator.com/item?id=43831524

"Today we’re releasing Pyrefly as an alpha. At the same time, we’re busy burning down the long-tail of bugs and features aiming to remove the alpha label this Summer. "

Re: Pyrefly: A new type checker and IDE experience for Python

#3

Post by globalnode » Sat, May 17, 2025, 1:53 PM UTC

Its probably cool n' all but fb isnt getting any of my attention. They'd need to come up with AGI for that to happen, and even then I'd shrug it off.

Re: Pyrefly: A new type checker and IDE experience for Python

#4

Post by kingkongjaffa » Sat, May 17, 2025, 2:04 PM UTC

This is very cool but why wouldn’t they just contribute to uv and ruff and ty https://github.com/astral-sh/ty

Re: Pyrefly: A new type checker and IDE experience for Python

#5

Post by ldng » Sat, May 17, 2025, 2:08 PM UTC

kingkongjaffa wrote: post #4

This is very cool but why wouldn’t they just contribute to uv and ruff and ty https://github.com/astral-sh/ty

NIH + copyright

Re: Pyrefly: A new type checker and IDE experience for Python

#6

Post by djinnish » Sat, May 17, 2025, 2:14 PM UTC

kingkongjaffa wrote: post #4

This is very cool but why wouldn’t they just contribute to uv and ruff and ty https://github.com/astral-sh/ty

I think astral and meta were both working on their own type-checkers independently. My current understanding is that meta released so they could preempt the initial release of ty. It seems like they're a bit further ahead in development. Not sure if there are going to be any real differences between the two down the line.

Re: Pyrefly: A new type checker and IDE experience for Python

#7

Post by simonw » Sat, May 17, 2025, 2:14 PM UTC

kingkongjaffa wrote: post #4

This is very cool but why wouldn’t they just contribute to uv and ruff and ty https://github.com/astral-sh/ty

ty is so new right now - it only got its current name a few weeks ago!

Re: Pyrefly: A new type checker and IDE experience for Python

#8

Post by ThePhysicist » Sat, May 17, 2025, 2:15 PM UTC

Seems there are at least three Rust-based competitors for type checkers in Python now (Microsoft, Facebook, Astral), and of course there's still mypy.

Re: Pyrefly: A new type checker and IDE experience for Python

#9

Post by trostaft » Sat, May 17, 2025, 2:19 PM UTC

ldng wrote: post #5

kingkongjaffa wrote: post #4

This is very cool but why wouldn’t they just contribute to uv and ruff and ty https://github.com/astral-sh/ty

NIH + copyright

Isn't both this and ty MIT license?

Re: Pyrefly: A new type checker and IDE experience for Python

#10

Post by phlakaton » Sat, May 17, 2025, 2:20 PM UTC

I'm curious to know more about the Pyre to Pyrefly transition, specifically the rewrite in Rust. Was that merely a case of trading in a lesser-known language for the language du jour? Were there specific advantages they wanted to get out of Rust?