prettyplease VS topiary

Nice blog, another very useful crate to use when working with proc-macro is https://github.com/dtolnay/prettyplease, for formatting generated code (very useful for debugging!), that does not bails out like rustfmt sometimes does.

I doubt you would want to actually use this human-consumed code, but an interesting alternative that I know of is David Tolnay's prettyplease. It tries to be lightweight and consistent for auto-generated code.

btw there is also https://github.com/dtolnay/prettyplease

This, I also have a bunch of files that seem to break rustfmt. Ime, it doesn't exactly refuse to format the whole file but it's picky in what and to what degree it chooses to format, basically anything flying in the complex blocks. I have run into prettyplease but I'm yet to actually try it on these offenders.

prettyplease

Optionally, format the generated code to make it more readable. You can run rustfmt on the output file, or use prettyplease before writing the file.

You should check out https://github.com/tweag/topiary

Yes, theoretically if you had ~identical grammars you could use it to do a full transpilation. There's a lot of challenges with that though. Writing a correct grammar for 1 language is complicated enough, but writing one for two where all your nodes and fields end up the same is likely insurmountable.

In practice, languages are either:

- Far enough apart that any pure AST transformation is insufficient and you need an AI component to produce usable output

This is something we've discussed[1] in the development of Topiary, deferring the process to the formatter. It's not a priority issue for us right now, but given the lack of universal editor support for elastic tab stops, having the formatter do this seems like a reasonable solution.

[1]: https://github.com/tweag/topiary/issues/170

build on top of https://github.com/tweag/topiary/blob/main/languages/rust.scm