frontpage.
newsnewestaskshowjobs

Open Source @Github

fp.

Open in hackernews

LSP client in Clojure in 200 lines of code

https://vlaaad.github.io/lsp-client-in-200-lines-of-code
164•vlaaad•1y ago

Comments

whalesalad•1y ago
This is the most Java-y Clojure I’ve probably ever read. Just use Java? It’s so verbose and complex for what it is doing. Breaking this down into smaller functions and using core.async would make it even more succinct.

Just want to emphasize this because clojure is indeed a small, lesser known language that has a hard enough time attracting users. This is not what anyone would consider an idiomatic example of using clojure.

roenxi•1y ago
Would it be 200 lines of Java? It'd be 200 lines of just for the boilerplate. It isn't really a selling point of Clojure because it is subjective, but low-syntax high-terseness look of the code is in itself a reward for using the language.

And there isn't anything especially wrong with sticking to Java primitives if someone is comfortable with them. They work fine for Java programmers. The dude doesn't need to learn a new async library to write an LSP client if he doesn't feel like it. Code works, its easy to read, easy to understand and modify.

koito17•1y ago
Line count is not very useful to compare without the context of standard library size, third-party dependencies, etc. The code in TFA depends[1] on a JSON library[2] that is about a thousand lines of code (excluding tests) wrapping a Java library for JSON decoding.

Then there's other things to consider, like the fact that this LSP client, while succinct, pays not only the cost of loading Jackson, but also the cost of loading clojure.core, which is quite non-trivial[3]. Startup time for LSP servers and clients definitely matters to some, considering that e.g. even clojure-lsp recommends running native executables over JAR files[4]. Can't find documentation proving it's for quick startup, but it's a plausible rationale for their recommendation of a binary over a JAR.

Note: I have used Clojure professionally and in hobby projects. I think it's nice that one can interactively develop a minimal LSP client and the resulting amount of work is roughly 200 lines of code. I say "minimal" because it's unclear how this client deals with offsets reported by LSP servers, which are all given as offsets in a UTF-16 encoded string. In any case, I still think advertising "LSP client in 200 lines of code" hides valuable information regarding functionality, implementation, "actual" code size, and trade-offs made in the choice of technology stack.

[1] https://github.com/vlaaad/lsp-clj-client/blob/a567e66/deps.e...

[2] https://github.com/metosin/jsonista/blob/c8f2b62/project.clj...

[3] https://clojure-goes-fast.com/blog/clojures-slow-start/#cloj...

[4] https://clojure-lsp.io/installation/#embedded-jar-legacy-exe...

pron•1y ago
Between records and compact classes [1] Java's boilerplate isn't what it once was.

[1]: https://openjdk.org/jeps/512

newlisp•1y ago
It's idiomatic "low-level" Clojure, though. Not everything is a happy place where you're just manipulating maps and vectors like in most examples.
0x1ceb00da•1y ago
> lesser known language that has a hard enough time attracting users

For very good reasons.

dig1•1y ago
I don't see why this wouldn't be considered idiomatic clojure code; it makes proper use of all the facilities provided by the language and the main intention of this code is to follow the article. Additionally, the clojure core team often encourages not to shy away from using java code directly, as this approach strikes a good balance between performance and language expressivity.

> It’s so verbose and complex for what it is doing. ... and using core.async

I think this code is actually quite straightforward and easy for a clojure developer to understand. In fact, using core.async in this case would be overkill and could complicate things further.

daveliepmann•1y ago
This looks like the other completely normal, idiomatic Clojure programs I've seen which manipulate a StringBuilder. And as Clojurians go I'm far to the succinctness/concision-preferring end of the spectrum.

I'm curious to see your core.async-based version :)

askonomm•1y ago
Holy crap is this unreadable or what (notably the lsp-base fn). There's a reason why in most Clojure companies I've worked at we try to make as small functions as possible, because otherwise it very very quickly becomes an unreadable mess, and you write code after all for humans to read, because if you didn't, you might as well just write binary. But, I'm not surprised many people don't want to get into Clojure or Lisps in general, because it takes a boatload of conventions and active discipline to make it a good experience.
slifin•1y ago
To me something unreadable is code that I cannot statically make any assertions about the runtime behaviour of the code

This function you're complaining about looks like 2 virtual threads doing program input reading and output writing for the LSP client given some ArrayBlockingQueues in about 25-30 lines

If I wanted the complete story I could use Clojure's inbuilt test runner to slip some ArrayBlockingQueues in there and run it under record with Flowstorm

Then leisurely seek through the entire state of the program, to get the play-by-play of how this works

There are so many good design choices in this language and a good 30% of colleagues I run into are not even doing the basics of like running a REPL, I think some people just need to clock in with a decade of C# or PHP or TS or JS or Python or whatever to get a taste of a language with next to no inbuilt immutability, statements instead of expressions, no reload-ability in the language semantics and just crapshot debuggers that run in lockstep with the program execution

Show HN: Gptbased – LLM leaderboard that emails you when to switch

https://gptbased.com
1•gptbased•4m ago•0 comments

Midjourney Ultrasonic CT Scanner

https://www.midjourney.com/medical/blogpost
2•lnyan•4m ago•0 comments

Learning VPP: Filtering Packets at 100GbE Line Rate

https://haryachyy.wordpress.com/2026/06/17/vpp-packet-filtering-100gbe-line-rate/
1•tanelpoder•5m ago•0 comments

Midjourney Medical

https://www.midjourney.com/medical
5•ricochet11•13m ago•1 comments

Next-Latent Prediction Transformers Learn Compact World Models

https://jaydenteoh.github.io/blog/2026/nextlat
1•sorenjan•14m ago•0 comments

Manhattan's fastest bike messenger (1985) [video]

https://www.youtube.com/watch?v=xMvJ83XpGoI
2•droidjj•21m ago•0 comments

Show HN: Draft, Open Source Agent Context Sync/Collaboration

https://github.com/idodekerobo/draft
1•idodekerobo•21m ago•0 comments

Vevey – AI game dev for kids to build games, together

https://www.vevey.ai/
1•dvdhutch•21m ago•0 comments

Code Intelligence MCP Server

https://github.com/DeusData/codebase-memory-mcp
3•vantareed•22m ago•0 comments

Show HN: Rank scratch tickets in your state by expected value

https://scratchstats.ai
1•nlenn618•26m ago•0 comments

Former Tesla Exec Is Building the Home Heat Pump Musk Promised

https://www.notateslaapp.com/news/4313/former-tesla-exec-is-building-the-home-heat-pump-musk-prom...
1•voisin•30m ago•0 comments

Miuse: Agents for Guidance with Physical Tasks

https://miuse.tech/
1•pratt3000•30m ago•1 comments

Show HN: A world cup app built by football lovers

https://testflight.apple.com/join/f4gKRZwr
1•bootsybus•35m ago•0 comments

Show HN: I built a smart screen recording macOS

https://screeen.co
1•vinzdg•37m ago•0 comments

Tim Cook warns Apple may raise prices as memory costs surge

https://www.businessinsider.com/macbook-iphone-apple-price-hike-tim-cook-2026-6
3•mgh2•37m ago•2 comments

Finent – A privacy-first budgeting app built around your payday

https://www.budgetwithfinent.com/
1•vexelior•43m ago•0 comments

Free calculators for creator income, freelance rates, AI tool ROI, and so on

https://richinto.com/
4•iplaypc•44m ago•0 comments

A Kamal wrapper for multiple apps on a single server

https://singleserver.com/
2•DVassallo•45m ago•0 comments

CVE-2026-23111: exploiting and detecting a nftables UAF born from a security fix

https://medium.com/@miggo-engineering/detecting-the-nftables-catchall-use-after-free-cve-2026-231...
2•rafaeldavidtin•49m ago•0 comments

Watch Baseball Games in Realtime in 8-Bit View

https://kottke.org/26/06/watch-baseball-games-in-realtime-in-8-bit-view
2•ohjeez•49m ago•1 comments

Ask HN: AI models are built on all of us, should their weights act like patents?

3•rhuber•49m ago•0 comments

Rust port of transformers (1M lines of code)

https://github.com/cool-japan/trustformers/tree/master
4•hardwaresofton•59m ago•1 comments

Show HN: An open source job search plugin for Claude Code

https://github.com/agent-data/job-search
5•jb_hn•1h ago•1 comments

Comparisons as Predictable as the Sunrise

https://pudding.cool/2026/05/similes/
3•zdw•1h ago•0 comments

New SOTA: TrustedRouter Fusion Beats Fable and Frontier

https://trustedrouter.com/blog/fusion-evals-open-source
3•amirhirsch•1h ago•1 comments

Ask HN: Has anyone had success with SBIR grants and what is the process like?

4•lyfeninja•1h ago•2 comments

Show HN: Lastwordonearth.com

https://lastwordonearth.com
3•hnrich•1h ago•5 comments

Second carcass-eating fly species cleared by FDA for maggot wound therapy

https://arstechnica.com/health/2026/06/second-carcass-eating-fly-species-cleared-by-fda-for-maggo...
3•Bender•1h ago•0 comments

Playing with the language modeling abilities of gzip

https://robinpie.neocities.org/gzipt
4•robinpie•1h ago•0 comments

Snap Reveals AR Glasses

https://techcrunch.com/2026/06/16/snap-finally-debuts-its-long-awaited-ar-glasses-specs-and-oof-t...
3•jrm-veris•1h ago•0 comments