Great news, everyone - CIDER 1.22 (“São Miguel”) is finally out!

And “finally” is the operative word here. This release took me way longer than I wanted it to, but that’s because I decided to stop kicking a few cans down the road and finally tackle some long-standing problems that had been bugging me for years:

  • Session and connection management - the logic for figuring out which REPL a buffer is associated with had grown into something I could barely follow myself.
  • The decoupling of nREPL from CIDER’s UI layer - a piece of technical debt so old it predates most of you reading this (the tracking issue, #1099, is from 2017).
  • A full audit of the codebase and the documentation, hunting for inconsistencies, dead code, broken menu entries, and gaps in the docs.

None of this is the kind of work that makes for a flashy release announcement, but it’s exactly the kind of work that keeps a 14 year old project healthy. I genuinely think this is one of the most important CIDER releases in recent memory, even though most of the changes aren’t really user-visible.

Highlights

Picking a handful of items out of a very long changelog, here’s what I’d call the highlights:

  • A huge editor responsiveness fix (#3933) - Clojure buffers no longer lag when there’s no REPL connected. The friendly-session matching used to scan the project classpath on every redisplay; now it does something far cheaper. If you’ve ever felt CIDER make your editing sluggish, this one’s for you.
  • Default sessions (#3865) - cider-set-default-session lets you bypass sesman’s project-based dispatch and pin a REPL as the default. Handy for all those workflows that never quite fit the project model.
  • nREPL is now decoupled from CIDER’s UI (#3892) - the transport layer no longer reaches into CIDER-specific handlers and UI strings. This finally closes #1099 and opens the door for other tools to build on our nREPL client.
  • Faster connection completions (#3888) - repeated cider-connect completions no longer re-spawn a round of ps/lsof subprocesses every single time.
  • A massive discoverability pass on menus and keybindings - menus across the inspector, REPL history, log, spec browser, and more now actually expose the commands they were missing (often a dozen+ per mode), and C-h m now lists the active bindings for several modes. A lot of functionality that was technically there but practically invisible is now front and center.
  • cider-repl-history-doctor (#3921) - a new command that walks your REPL history, finds entries with unbalanced parens, and helps you clean them up. Born out of a real bug report about history rendering breaking.
  • Support for let-go (#3926) - a Clojure dialect implemented in Go is now recognized as a known nREPL runtime.
  • Better remote (TRAMP) jack-in and connect (#3885, #3886, #3887) - endpoint detection, command resolution, and SSH tunneling all behave correctly against remote hosts now.
  • Plenty of nREPL robustness fixes - plugged several request-id leaks, bounded the completed-requests table, and made a misbehaving response handler no longer able to drop later responses on the floor.
  • Bumped the injected nREPL to 1.7.0 and cider-nrepl to 0.59.0.

The full list is much longer - check out the changelog if you want the gory details.

A fun little detour: Port and Neat

While I was doing the nREPL decoupling work, I got curious and started experimenting with adding support for prepl (Clojure’s built-in socket REPL) as an alternative to nREPL. I even put together a prototype (cider#3899). It sort of worked, but it also reaffirmed my belief that prepl and nREPL are different enough that bolting prepl onto CIDER would mean papering over its limitations in dozens of subtle places. So instead of forcing it, that little experiment grew into two brand new projects of mine:

  • Port - a minimalist prepl client for Emacs.
  • Neat - a tiny, deliberately language-agnostic nREPL client.

Both have write-ups of their own, so I won’t repeat the details here. I’m pretty excited about where they might lead - a great example of how digging into old technical debt can spark entirely new ideas.

Epilogue

This release is dedicated to São Miguel, the stunningly beautiful main island of the Azores archipelago.1 I got a lot of my recent inspiration for CIDER there, and naming the release after it felt right.

As always, none of this happens in a vacuum. A huge thank you to Alex Yakushev for his continued work on the inspector - it keeps getting better and better. And of course a massive shoutout to Clojurists Together and to all the other contributors and backers of my open-source work. You’re the reason CIDER and friends keep moving forward.

That’s all I have for you today. I hope you’ll enjoy using CIDER 1.22 as much as I enjoyed (eventually) shipping it. Keep hacking!

  1. If you ever get the chance to visit, do it. Crater lakes, hot springs, and the greenest hills you’ve ever seen. ↩