sbt server reboot


This is a continuation from the sbt 1.0 roadmap that I wrote recently. In this post, I'm going to introduce a new implementation of sbt server. Please post on sbt-dev mailing list for feedback.

The motivation for sbt server is better IDE integration.

A build is a giant, mutable, shared, state, device. It's called disk! The build works with disk. You cannot get away from disk.

-- Josh Suereth in The road to sbt 1.0 is paved with server

The disk on your machine is fundamentally a stateful thing, and sbt can execute the tasks in parallel only because it has the full control of the effects. Any time you are running both sbt and an IDE, or you're running multiple instances of sbt against the same build, sbt cannot guarantee the state of the build.

The original concept of sbt server was proposed in 2013. Around the same time sbt-remote-control project was also started as the implementation of the idea. At some point, sbt 0.13 stabilized and Activator became the driver of sbt-remote-control, adding to it more constraints such as not changing sbt itself, and supporting JavaScript as the client.

With sbt 1.0 in mind, I have rebooted the sbt server effort. Instead of building something outside of sbt, I want to underengineer the whole thing. This means throwing out previously made assumptions that I think are non-essential such as automatic discovery and automatic serialization. Instead I want to make something small that we can comfortably merge into sbt/sbt codebase. Lightbend holds Engineering Meeting a few times a year where we all fly to a location and have discussions face to face, and also do an internal "hackathon." During the Februay code retreat in beautiful Budapest, Johan Andrén (@apnylle), Toni Cunei, and Martin Duhem joined my proposal to work on the sbt server reboot. The goal was to make a button on IntelliJ IDEA that can trigger a build in sbt.

sbt 1.0 roadmap


There’s been some discussions around sbt 1.0 lately, so here is a writeup to discuss it. This document is intended to be a mid-term mission statement. A refocus to get something out. Please post on sbt-dev mailing list for feedback.


I don’t have a good idea on the timing of when sbt 1.0 will ship.
The biggest feature of sbt 1.0 is code reorganization, which is is already in progress:

ScalaMatsuri as a lifestyle


For me (and for many of the 27 organizers, I imagine) ScalaMatsuri is a lifestyle. It's true that there was a successful two-day conference in Tokyo with 550 participants. But for us the organizers, the preparation has been going on since February 28th, for 11 months. Despite the fact that my contribution was small, planning ScalaMatsuri 2016 was by far the most amount of involvement I've committed to. Through the course of planning months, there were many discussions over Slack, Hangouts, and occasionally even face-to-face. The fun part was coming up with the ideas together, and seeing them materialize. Sometimes, I was the one coming up with radical ideas that were being executed by someone else, while other times, it was the opposite case and I was getting my hands dirty.

I've already written a lot of what I wanted to say in A regional tech conference that's also global, so there might be some overlap over here.

a regional tech conference that's also global


stricter Scala with -Yno-lub


For a flexible language like Scala, it's useful to think of subset of the programming language, like your own personal Good Parts, and opinionated style guides.


To try -Yno-lub, you can drop in the following sbt plugin to project/ynolub.sbt:

addSbtPlugin("com.eed3si9n" % "sbt-ynolub" % "0.2.0")


When Scala's type inferencer finds type A and type B to unify, it tries to calculate the lub (least upper bounds) of two types with regards to <:<. This process is sometimes called lubbing. Here are some of the examples:

scala> if (true) Some(1) else None
res0: Option[Int] = Some(1)
scala> if (true) List(1) else Nil
res1: List[Int] = List(1)

One idea I've been thinking about for a few years is that lubbing in its current form is not helpful.

herding cats: day 1


Check out my new series herding cats. (I'm writing it using Pamflet from the get go)

This is a log of me going through Cats, a functional programming library for Scala that is currently experimental and under active development.

The road to sbt 1.0 is paved with server



I gave a talk at Scala Days 2015 San Francisco with Josh Suereth (@jsuereth).

switching Java version


I've been switching between Mac and Ubuntu, and between Java 6 and 7 lately.
This is a memo of how to switch Java versions on both Mac and Ubuntu.

Update: Yoshida-san told me about this thing called jEnv, which does all this.


Here's one way of loading different shell files depending on the OS:

## basic
[ -f $HOME/dotfiles/zshrc.basic ] && source $HOME/dotfiles/zshrc.basic

## aliases
[ -f $HOME/dotfiles/zshrc.alias ] && source $HOME/dotfiles/zshrc.alias

case "${OSTYPE}" in
# MacOSX

monads are fractals


On my way back from Uppsala, my mind wandered to a conversation I had with a collegue about the intuition of monads, which I pretty much butchered at the time. As I was mulling this over, it dawned on me.

Sierpinski triangle

monads are fractals

The above is a fractal called Sierpinski triangle, the only fractal I can remember to draw. Fractals are self-similar structure like the above triangle, in which the parts are similar to the whole (in this case exactly half the scale as parent triangle).

towards universal access at a conference


Two days of #ScalaMatsuri ended as a huge success. But for the next year, I'm leaving ourselves a few homeworks to work on. As the title suggests, the next goal that we should aim for is universal access. In Scala language, universal access principle indicates the fact that both methods and fields can be accessed interchangeably from outside.

For a conference, I mean universal access to mean being more inclusive to various groups of people:

  • women/men/straight/LGBT programmers
  • Japanese/English speakers
  • beginners and experts
  • postdocs
  • people from other Asian countries
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