Escape IntelliJ: Scala and Kotlin LSPs on Emacs Eglot

https://jointhefreeworld.org/blog/articles/emacs/emacs-eglot-scala-kotlin/index.html

by jjba23 • 2 days ago

117 95 2 days ago

phmx• 7 hours ago

The Metals documentation includes instructions for setting it up with Emacs. I followed them, and everything works, including worksheets.

https://scalameta.org/metals/docs/editors/emacs

marginalia_nu7• 7 hours ago

The fact we still don't have a decent Java language server is one of my canaries for the fact that LLMs still, generally speaking, can't ship. There is undeniably demand for this sort of thing, but nobody is coming to meet it. (jdtls, bless it for trying, is just not good)

TiredOfLife2• 6 hours ago

The one in VS Code seems fine. It's not quite intellij level, but what is.

And speaking on llm and lsp. The new PHP lsp PHPantom (with help of llms) is approaching jetbrains offering fast.

marginalia_nu7• 6 hours ago

That's just a wrapper for jdtls. I mean it works on some projects, but fails on many gradle builds and is basically just running the Eclipse IDE headlessly.

This is probably the one contender:

https://github.com/georgewfraser/java-language-server

and it kinda works, but it's also a bit lacking.

timanderson• 6 hours ago

How is the Oracle one? It has better reviews in VS Code marketplace than the Red Hat one (jdtls)

whazor• 6 hours ago

why do you need a java language server? Let them use the same tooling you would use in CI

Cthulhu_2• 5 hours ago

These are two different things; a language server would be a standardized intermediate layer between said CI tooling and any editor for inline / realtime checking, code suggestions and formatting.

adamddev1• 5 hours ago

Exactly. I've been trying to say this. Some people think that because people can write CRUD APIs and end-user apps with AI, no-one will need to write code anymore.

There is so much to be built in terms of tooling and libraries where we need tight, solid, well-crafted, original, unique code.

marginalia_nu7• 5 hours ago

They have a real weakness when it comes to designing something that doesn't have a design precedent. There are no good java language servers, so it can't design a good java language server.

You can also show this with by e.g. asking an LLM to design an internet search engine in Java, for which there doesn't exist very many examples, and my own Marginalia Search and my devlog is one of few design examples it has to reach for.

Even mentioning nothing of MS just using similar constraints, you'll get a nearly identical design to Marginalia Search. Algorithm choices will be the same. Document and term IDs will encoded in a similar succinct fashion (in one of my experiments, the chosen design was binary compatible). Architecture will be the same. Services and components will to a significant degree have the same names and even using the same non-standard vocabulary. It isn't word for word identical, there sure are a lot of coincidental similarities that notably don't exist with search engines implemented in other languages.

jlgarhdez2• 5 hours ago

I am actively working on a fast language server for Java and kotlin.

I’m driving it daily and it’s much faster than IJ for what I need, although it doesn’t provide all the diagnostics that IJ does…

It’s on github.com/pepegar/ktlsp if you’re curious.

jlgarhdez2• 5 hours ago

To be clear, it’s not supported by a compiler, but rather plain tree sitter syntax parsing. I’m embarking on a bigger project to create a linter (and integrate) without relying on JVM or a compiler at all, but IDK when that’s gonna come.

dtech2• 5 hours ago

Nah, there is little demand for it that's the reason.

LLMs don't need a LSP, they work better without it often. Most Java devs use IntelliJ or another IDE with its inbuilt thing. For everyone else the existing one is good enough for incidental usage.

So ~no one cares

marginalia_nu7• 5 hours ago

I care, which is existence proof that someone cares.

mechanicum2• 2 hours ago

My understanding was the biggest issue has always been that javac is a poor foundation for any kind of live tooling like LSPs?

It’s less “make me a Java LSP” than “rewrite javac around incremental compilation and exposing a semantic DB”. Which sounds like a much harder problem.

marginalia_nu7• 2 hours ago

We have a java compiler API nowadays that solves this.

TiredOfLife2• 7 hours ago

and forces you into a closed proprietary ecosystem

https://github.com/jetbrains/intellij-community ?

jillesvangurp2• 5 hours ago

Exactly, I've been using their community edition for years for Kotlin development. Works fine for normal day to day development needs. I had a paid subscription for a while that I just let expire because I rely more on agentic coding tools these days and I just don't write a lot of code by hand at this point. The paid version adds a lot of deeper integrations and tools that you may or may not need. Personally, I don't really miss most of that. These days the community edition and the paid edition are the same. But if you don't take a subscription, the paid stuff is unavailable.

As a company, Jetbrains is a private company. It's one of the few large software companies that managed to get there without selling out to VCs or the vultures on the stock market. Of course they want to make a profit but they also create a lot of value for developers. Including a lot of open source things. I think it's nice that it's still possible to create a business by bootstrapping and without compromising your values.

pjmlp10• 4 hours ago

I keep finding interesting that some devs refuse to pay for tooling like every other profession, yet they don't take pull requests as salary either.

ares623• 7 hours ago

oh I thought this was somehow extracting the proprietary LSP engine that IntelliJ has and using it with Emacs.

andylynch• 6 hours ago

I think Jetbrains did that already; the Kotlin LSP server is derived from the (also open source) IntelliJ plugin

sajithdilshan• 6 hours ago

But what do you actually get with IntelliJ? A massive, monolithic Java application that frequently hogs 8GB+ of RAM, locks up your system while “indexing pre-built binaries,” and forces you into a closed proprietary ecosystem.

This is just exaggeration. I use IntelliJIDEA everyday (on mac) with multiple projects open and tbh they have optimized the IDE a lot to make it faster. I'm not saying it's perfect, but it's getting better. Also it's not closed source. The core of the IDE is open source (https://github.com/jetbrains/intellij-community) and for some specific framework support (e.g. Spring) are available on Ultimate.

CafeRacer• 6 hours ago

This is actually not an exaggeration. Ive been using WebStorm when it worked well, then it became progressively slower to the point of being unusable even on small projects.

Bishonen88• 6 hours ago

Counterpoint: use intellij on full stack apps with cdk, react, sqls and whatnot, multiple open at a time, without any problem.

Cthulhu_2• 5 hours ago

I feel the same about VS Code, it's probably some of the plugins but sometimes, especially when LLMs make edits, memory usage explodes until my system breaks down and force pauses some apps until I kill some of them.

I should go back to Zed, maybe use the CLI interface for agentic programming instead of the UI.

sgt• 5 hours ago

I've got Android Studio open now, while also working in several PyCharm projects, IntelliJ and WebStorm. No issues at all on macOS.

tsvetkov• 5 hours ago

It's a bit strange to project a personal experience with one product onto all other products by the same vendor, even if those products use shared platform parts. Not to dismiss your claim, it's just IDEs (code engines specifically) are naturally pretty complicated pieces of software, so the experience may vary.

The claim that 8Gb RAM is required just for Intellij seems to be at least overgeneralization (also depends a bit on how you count RAM usage; e.g. do you count all mmaped files as RAM usage even when pages are not loaded?). Can be true for some projects, but I've been working on decently sized Java/Kotlin codebases (~250k locs) with way less RAM allocated for Intellij (again, your experience may vary). Even Intellij and Kotlin projects themselves have been usable with less memory, at least some time ago.

What's more baffling, though, is how an LSP would be significantly better if it is based on the same IDE core, just running headlessly? I think there may be an independent non-IDE based LSP for Scala, but both Java and Kotlin LSP are based on existing IDEs engines (Java LSP is based on Eclipse engine, Kotlin LSP is based on Intellij).

A quote from the kotlin-lsp GitHub repository: > The language server is based on the most recent IntelliJ IDEA version and proprietary parts of JetBrains Air and Fleet products, making it partially closed-source.

https://github.com/Kotlin/kotlin-lsp

gf000• 5 hours ago

Also, like where else would the indices live? They are in memory to make going to definition, source, analysis etc fast. It's not even using java objects for these, so a feature-equivalent solution would be similarly "fat".

psychoslave2• 4 hours ago

I don’t know, using Vim and Exuberant Ctags can give you a significant part of these features for a very lower footprint. But to be clear, it’s not a ready-to-go path on parity with DX that IntelliJ provides.

Hackers are often exceptionally good at optimizing the hidden parts no one give a shit until everything crumble under systemic slowness, but they often also are very bad at designing even a decent UX for everything else regarding in-your-face aspects.

tiew9Vii• 5 hours ago

I've used InteliJ on and off for 20 plus years. It's progressively got bloated and slower, not faster.

20 years ago it was the fast lean option when there was Netbeans and Eclipse. Today it's ok, still good feature wise but fast and lean it is not anymore when I've used it for Scala oand Kotlin.

gib444• 4 hours ago

Yup. It's been particularly bad since around 2023/2024 and only got worse with all the AI crap, though I think that's been almost a useful scapegoat for them recently

akshaydeshraj• 5 hours ago

IntelliJ (actually Android Studio based on IntelliJ) was my first real IDE and real programming experience. I was so blown away !

Almost 15 years later, nothing else matches the out of the box experience of IntelliJ, atleast for JVM based languages.

pjmlp10• 3 hours ago

Add in VS for .NET languages and C++ (hot reload, debugging capabilities), and the beloved Delphi/C++ Builder duo as well.

To this day there isn't anything like C++ Builder, if you want the famous VB dev experience, but with C++.

TacticalCoder• 2 hours ago

IntelliJ (actually Android Studio based on IntelliJ) was my first real IDE and real programming experience. I was so blown away !

I switched to IntelliJ back when people where still arguing which of the two between Eclipse or NetBeans was better (fools!): that is, before some of the commenters here were born.

Heck, I bought IntelliJ when the world was ending in the Mayan calendar, it was something like 75% off because the world was going to end in a few weeks anyway.

But since 10+ years I'm using only... Emacs.

Emacs now with tree-sitter, LSPs, native-compilation, magit and the LLMs at ease with Un*x CLI tools make it so that IntelliJ looks like a behemoth. From a glorious past but still a behemoth.

pjmlp10• 4 hours ago

Quite ironic, given that Emacs used to stand for "Eight Megabytes and Constantly Swapping" for the epoch hardware.

neutronicus• 4 hours ago

Also ironic given that emacs with a LSP server is more than capable of slowing a dev machine to a crawl

z3t4• 4 hours ago

People will complain about 2MB ram usage and then gladly spend 4k on a mac pc

rob74• 4 hours ago

Completely agree. Also: some people enjoy fiddling with their tools, installing extensions and configuring everything until it's just perfect. Other people (most, I would argue - the proverbial "silent majority") want to get something that works reliably "out of the box" and has most (not all, IntelliJ IDEs also have plugins of course) batteries included. They shockingly are even willing to pay money for this!

isityettime3• 2 hours ago

The dream is something batteries-included but still radically hackable. Emacs is slowly making this feasible via smaller and smaller "starter kits" as it adds new features. It's not perfect, and maybe this approach will never yield a fully productized solution like IntelliJ. But getting a full-featured Emacs setup hasn't meant building the world from scratch in a long time!

mdawwg• 3 hours ago

I'm also on a mac, but in the last few years performance and memory usage has gotten pretty bad. Though we use Intellij for mostly Angular / Node projects. A colleague of mine had reverted to an older major release because it runs better on our Macs. He ended up switching over to a popular open source IDE and hasn't looked back.

tecleandor• 5 hours ago

I'm trying to avoid IntelliJ because I only need it for editing TeamCity build configuration files, that are written in a Kotlin based DSL [0], and autocomplete and linting are be very helpful.

I've tried Eclipse and VS Code but I don't get them to autocomplete or detect syntax correctly. Would any LSP help me with that? As I have no idea about Java, Kotlin or Gradle, everything is kinda confusing to me...

  0: https://www.jetbrains.com/help/teamcity/kotlin-dsl.html

anthk• 5 hours ago

Can Java developers run a GUI builder outside the IDE and then use any other editor for the rest and then compile a project with Maven and the like?

pjmlp10• 3 hours ago

Of course, at least those of us that know Java since 1996, and the only thing we got was the 1.0.2 JDK on a magazine cover CD ROM.

rs_rs_rs_rs_rs2• 5 hours ago

IntelliJ Git integration is so good I wish it would be a standalone client.

0x1ceb00da• 4 hours ago

You can do "idea diff file1 file1" to open a popup with their diff tool.

wiether2• 4 hours ago

Funnily that's the one feature I dislike in IntelliJ and thus relies on another GUI

Otherwise I like having everything in one place: code, containers, databases, remotes...

rs_rs_rs_rs_rs2• 1 hour ago

What are you using instead?

jbvlkt• 4 hours ago

Sometimes I also feel that Idea is too slow, especially for smaller projects or languages where I do not need top tier support. ie. I am backend rust and python programmer. I also have to work with JS/TS and C++ projects but I mostly only read through them.

I started using neovim with plugins if syntax highlighting and good navigation is enough. I have also set up ideavim configuration to be as close to neovim as possible. Now I can easily switch between Idea and neovim with almost the same workflow.

DrProtic• 4 hours ago

People will go to great lengths to avoid paying for what is, arguably, an outstanding product from a great company, then think nothing of spending the same amount at Starbucks.

I don’t think I’ve ever seen a company scrutinized and nitpicked as much as JetBrains.

phplovesong2• 4 hours ago

Well its a russian company, and took part in the solarwinds hack, that was directly funded by the fsb. So, yeah, it should ve scrutinized, nitpicked and avoided at all costs.

Its 2026, there is no need for a proprieraty IDE that is stuck in the early 2000s.

marand23• 4 hours ago

They closed all their russian office locations at the start of the Ukraine war afaik so I wouldn't call it russian any more.

denisw• 3 hours ago

JetBrains is and has always been a Czech (and, thus, EU) company, not a Russian one. Yes, the founders are Russian, but that does not make the company so. They did have Russian offices, but closed them after the start of the Ukraine war [1].

The only confirmed link to the SolarWinds attack seems to be that SolarWinds was using TeamCity (JetBrains' CI/CD product) and that this was alledgedly used as a "gateway" to SolarWinds' systems - which doesn't require any cooperation from JetBrains, just an unpatched security issue. In fact, a patch by JetBrains for the exploited issue seems to have been available, but was not installed [2].

So while any company deserves scrutiny, these particular allegations against JetBrains smell like FUD to me.

See also JetBrains' own statements on the SolarWinds thing: https://blog.jetbrains.com/blog/2021/01/06/statement-on-the-...

[1] https://en.wikipedia.org/wiki/JetBrains

[2] https://www.cisa.gov/news-events/cybersecurity-advisories/aa...

cdmckay• 3 hours ago

Source: trust me bro

pjmlp10• 3 hours ago

So we get to replace it for a programmer's editor from the early 1980's instead, good call.

krzyk• 33 minutes ago

Its 2026, there is no need for a proprieraty IDE that is stuck in the early 2000s.

This is the best IDE for Java. And it is nowhere near 2000s, it is modern and the best one can use for Java.

laszlojamf• 4 hours ago

I agree that IntelliJ is a monster of a resource hog, but I have yet to find an editor where code navigation is as good. That's basically all I use it for these days, in the days of LLMs, and I still think it's worth it. VSCode, especially for golang, is terrible. I might be holding it wrong, but I've really tried, and it's just not good enough.

Before LLMs, when I still refactored by hand, coworkers who were using vim or vscode used to ask me to do big refactors, because IntelliJ always got it right, whereas with the other editors it was hit-or-miss.

terminalbraid• 4 hours ago

This is my experience and it really sucks that Jetbrains has devolved into such a poorly run company. It's clear a lot of their real talent who cared about the programming side and refactoring left years ago. Now it seems like all their product decisions are from bog standard non-technical business people who chase buzzwords.

This is a major problem for them because they fragmented their IDE codebase so much properly maintaining it requires resources and people they don't have and would have to invest years of effort to replace. But that doesn't maximize quarterly profit, so it's left to decay and we get hourly LLM plugin updates.

cmrdporcupine• 2 hours ago

I've used IntelliJ since 2004 and it's always been a resource hog and always perpetually just beyond the faculties of the typical developer workstation. They've struggled with it since forever.

I don't think they've devolved at all. They've always been a mix of brilliance (far ahead of everyone else on refactoring and semantic analysis, etc) and challenges. And it has a lot to do I think with just being a relatively small team.

And the wave of LLM/agentic stuff has been a serious threat to them. Their efforts with Junie and the things before that have been faltering steps.

I do think it's beyond the point where they probably should just rewrite the core things they do in Rust. Their issue since day one has been it seems they're in a perpetual fight with the JVM garbage collector.

selivanovp2• 2 hours ago

Significant portion of their staff left in 2022, when they decided to relocate from Russia and they keep bleeding engineers ever since. Despite registration in Prague, JetBrains has always been a Russian company with dominantly Russian employees.

f3408fh2• 3 hours ago

Saying that VS Code is terrible for Go is simply false. The Go extension is regularly updated and works extremely well. Sure, it lacks some advanced refactoring features available in IntelliJ, like function parameters reordering, but gopls supports most refactoring you'd need to do day to day..

sdf4j• 3 hours ago

I think OP talks about code navigation, which is objectively terrible on vscode in general

phplovesong2• 4 hours ago

Same for the jetbrains PHP based IDE (iirc named something in the likes of webstorm, or phpwind etc) is super slow and hogs ram like crazy. Also most devs using it have really, relly poor skills. Its weird i know, but i see it time and time again.

WalterGR• 3 hours ago

Also most devs using it have really, relly poor skills. Its weird i know, but i see it time and time again.

Specifically in the PHP community? Legitimately curious...

vanyaland• 3 hours ago

worth noting the kotlin-lsp here is jetbrains own, basically intellij analysis engine running headless. you're just dropping the intellij gui

hocuspocus• 7 minutes ago

Java LSPs are essentially the same approach, headless Eclipse JDT or NetBeans.

While Metals for Scala was an overhaul from the former Eclipse plugin (and Ensime) plus early experiments embedded in the Scala 3 compiler. And Metals v2 is yet another rewrite.

Metals is architectured in a completely different way, see the BSP: https://build-server-protocol.github.io

mastermage• 3 hours ago

I enjoy JetBrains IDEs alot. Altough I mainly use Dataspell and Datagrip and not Intellij but they make my life easier. Specifically when connecting to new DBs

minraws2• 3 hours ago

I wrote an LSP for kotlin and java recently and it's so annoying how tightly coupled all the LSP stuff is in IntelliJ to the IDE itself they have a outside LSP project which seems to be going very slow or nowhere is very sad.

Note I tried to use IntelliJ to build it the performance was not nearly as nice as I would have liked still better than a lot of LSPs but still.

I know a bunch of folks have tried it but I think only Jetbrains can build a good one, unless someone actually goes all in on solving this for a few months and rebuilds the parsing and types systems outside of the Jetbrains toolchain and ecosystem.

Java is likely easier but it's also quite jank in terms of how existing solutions work.

But I like projects like this, I am not against IntelliJ it must be great had been great when I was learning but I want a lsp to use for scripts and the small edits, opening a massive IDE is very overkill for the kinds of small changes I like to make now.

pjmlp10• 3 hours ago

I will quote the blog post announcing Kotlin as project, so naturally it is tied to InteliJ.

"The next thing is also fairly straightforward: we expect Kotlin to drive the sales of IntelliJ IDEA. We’re working on a new language, but we do not plan to replace the entire ecosystem of libraries that have been built for the JVM. So you’re likely to keep using Spring and Hibernate, or other similar frameworks, in your projects built with Kotlin. And while the development tools for Kotlin itself are going to be free and open-source, the support for the enterprise development frameworks and tools will remain part of IntelliJ IDEA Ultimate, the commercial version of the IDE. And of course the framework support will be fully integrated with Kotlin."

https://blog.jetbrains.com/kotlin/2011/08/why-jetbrains-need...

minraws2• 3 hours ago

Given how much outside support they have received they could also make a paid lsp available like they had Resharper, I would be willing to pay for a paid lsp if I use the language enough.

10$ a month for an LSP with all the bells and whistles, should be easier to maintain than an entire IDE tbh. And they can sell me on advanced features in their IDEs through it.

I just don't want to have to open a bulky IDE anymore, IDEs just suck for me as a development tool.

microflash• 3 hours ago

As a very heavy user of IntelliJ and associated family of IDEs, I’d say they are extremely bloated compared to a few years ago. My latest annoyance with IDEA has been extremely slow disk sync. If I edit something outside the IDE, it takes a while to appear in it.

They should cut down the binary size and ship a leaner version without all the bundled plugins. They should improve performance on extremely large projects (both memory and IO).

Although I have let my personal Ultimate subscription expire, I still use it at work because debugger, codenav and autocompletion are still best in class.

mcv• 3 hours ago

It's great that Emacs gets more support of course, but personally I've never really got the hang of it. I actually like IntelliJ. To the point that I can't even bear VS Code. And for simple editing, vi is still my thing. I don't think that will ever change. I assume Emacs sits somewhere between the two.

sevenzero• 2 hours ago

I was thinking of unsubscribing from IntelliJ just today because my file tree doesn't update for like 5 minutes when I create new files with my terminal. Its utterly broken.

c16• 2 hours ago

I've been using Goland/IntelliJ since I graduated. Been paying for it for years. But the resource hog and I guess focus on writing a mediocre AI side panel really killed it for me.

The main improvements lately were:

- line/function prediction

- Claude Code plugin

And I can use Claude Code in any terminal. So I've switched to zed.dev and use Claude there. Wish it had the line prediction though.

roegerle• 10 minutes ago

users should just turn off all the plugins they'll never or rarely use.

Escape IntelliJ: Scala and Kotlin LSPs on Emacs Eglot

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