Ensime – a different design

Sam Halliday and Rory Graves

Scala Sphere 2016

Click here for video recording


Rory Graves @a_dev_musing

  • Wrote mobile games before it was cool
  • Dynamic networks before clusters were cool
  • Shows people around an old windmill at weekends
  • Recently started Scalanator.io
  • Martial artist who is a trained swordsman


Sam Halliday @fommil

  • co-founded FHSST, 5mil Free textbooks in South Africa
  • co-founded a mathematics company
    • quantum mechanics, machine learning, etc
  • co-founded Neurofiction: brain scanners + fiction
  • netlib-java underpinning Apache Spark
  • most proud of getting to the Mun in Kerbal…


Straw Poll

  • IntelliJ
  • Eclipse
  • Other


  • ENSIME is not really an IDE
  • It is a toolset:
    • building IDEs
    • analysing code


  • Ensime in action
  • Architecture
  • Ecosystem - our community
  • The Future






c.f. Benjamin Mako Hill’s talk at LibrePlanet 2013

Community Principles

  • Code of Conduct (Typelevel)
    • good vibes
  • Lots of help for new contributors
    • ticket → general area of code
    • fast PR reviews and feedback
  • Pragmatic approach
    • everybody is a Scala dev
    • KISS: prefer failure / explanation, not complexity
  • Free as in Burger
    • Hack days in London! Join us remotely via gitter.im

Continuous Integration

Continuous Delivery


What going on

This year

  • Moved license to GPL
    • CLA Assistant
  • Java Support
  • Editors, editors and more editors!
  • Bugs fixes
  • Performance improvements

The Future


  • Nearly there
    • Ish
    • ongoing development
    • 20 open tickets, mostly minor bugs/improvements

Beyond thunderdome!

  • 1.0 is really a stable release for legacy
  • Allows bigger breaking changes
    • Drop Java 6
    • Drop 2.10? - probably not
  • Java 6 leads to nasty limitations.


  • We have basic java support
  • More is coming!
  • Thanks Aemon!


  • Really a catch all for everything not 1.0
  • Things often move forward
  • New debugging layer - may come earlier
  • Graphpocolpyse
    • enables all sorts of features
  • 2.12
  • Dotty?


  • ENSIME lacks some key features
    • find usages
    • dead code
    • etc.
  • Limited by knowledge that must be computed

Graphpocolpyse 2

  • Sam’s next big thing
  • Graph database of project structure
  • Opens up all shorts of fun stuff

Presentation Compiler Interface Rewrite

  • Rory’s next big thing
  • In progress
  • Cleaner interface
    • No more depending on ScalaC Internal
    • Allows support for Dotty

Sharing for the win!

  • The discussions with other tooling people has been awesome
  • A lot of sharing is possible



  • ENSIME is a protocol based IDE server
  • We are resource limited, but
    • Community is king!
    • We are making progress
    • The community has made a huge difference
  • Interesting to see how it fits into Simon Schäfer’s model (up next)



Come to the hacking session this afternoon!