Why building a Rust LSP is hard

mitxela•about 2 hours ago

Using a JSON TCP connection for what on Windows would be direct function calls (COM) or in Eclipse would be direct function calls between Java modules always felt a bit gross.

throwaway17_17•about 1 hour ago

I agree, the only reason LSP exists as it does is for a world running on electron based applications. Plug-ins and application extensions are not new technology and they are nearly universally more efficient in the forms designed and used prior to 2005-ish. I understand why VSCode exists and why it is used so often by developers, but it is certainly a downgrade from more language specific options that could exist.

There are some arguments that do carry water in favor of using a client/server protocol transmitting JSON, in particular, the ability for a nearly complete decoupling of analysis of code and the displaying and editing of that code. Also, LSP was (to my knowledge) the first language/platform/usecase agnostic protocol intended for use in code editors.

I get why this is where a big chunk of developers have ended up, but I do bemoan the lost potential for a language to grab mindshare and popularity on the usability and performance of its tooling and developer experience via-a-vis a custom designed and hyper specific code editor. I mean, Rust and Elm received endless praise for their error messages as a massive boon to developer experience, so it is a facet of language design and implementation that can act as great advertisement. I just hate that the prevalence of LSP at this point precludes custom editors as a first choice in the current zeitgeist.

octoberfranklin•about 2 hours ago

Enter hell: LSP assumes that it's the source of truth, but you still need to access the filesystem yourself, and do it in a synchronized way

LSP is an example of utterly horrid technical design.

Stop letting Microsoft design protocols and APIs. They are so. bad. at. it.

tredre3•about 1 hour ago

> Stop letting Microsoft design protocols and APIs.

Unfortunately nobody else stepped up to do it.

I'm glad that the code editors out there didn't wait for your theoretical better designed protocol and decided to adopt LSP. Otherwise we'd still have editor that only support one language properly, and the rest is treated like text. If the price to pay is that it sucks for the handful of people who have to work with it, so be it. For every LSP developer that suffers there are tens of thousands of downstream users who benefit from better language support in their favorite editor!

duttish•about 2 hours ago

I've never looked into LSP, how would you design it?

packetlost•about 2 hours ago

Well for one I wouldn't design it so both the LSP and the editor need a synchronized view of the underlying file.

mitxela•about 1 hour ago

Start with synchronous function calls instead of JSON. Microsoft knows how to do that - they invented COM and OLE. Function calls enable whatever data sharing is necessary to maintain a coherent view. Imagine trying to do OLE with JSON - just wouldn't work. (Does OLE still exist?)

rspeele•13 minutes ago

I feel like MS actually learned their lesson with synchronously integrating the language intelligence into the IDE. Old versions of VS would hang or crash based on bugs in the language tooling trying to provide intellisense. You'd restart and it'd work fine till you hit some other weird edge case. Generally this settled to a level of rare-bugginess where you were happy enough with the advantages not to go back to Emacs/VIM, but still annoyed at the occasional restart needed.

In no way does this mean LSP is a perfect solution, but anything synchronous would be a step backwards.

cyberax•about 1 hour ago

Moreover, it's not just stupid, it also does not actually solve _anything_.

A synchronous function can also have obsolete indexing information if it races with the code updates.

cyberax•about 1 hour ago

Stupid idea.

So the LSP crashes and/or goes into a runaway memory consumption loop. And your main application dies with it.

Or what if you want, you know, to be able to use the same LSP from TWO different applications at the same time?

Never mind issues with other managed runtimes not expecting to deal with something else in their address space.

Why building a Rust LSP is hard

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