This document provides an overview of sbt 1, including: - Who is developing sbt 1 (Lightbend Tooling team led by Eugene Yokota and Dale Wijnand) - Key updates in sbt 1 like using Scala 2.12, Zinc incremental compiler, improved library management, and removal of old parts - Goals of sbt 1 like minimizing conceptual jump from sbt 0.13 - Size of the sbt ecosystem with hundreds of thousands of downloads and over 400 community plugins - Ways to get involved like helping with documentation, issue triage, or contributing patches

1. sbt 1
Eugene Yokota (@eed3si9n)
Dale Wijnand (@dwijnand)
June 2018

2. • Lightbend Tooling team
who are these guys
Eugene
(@eed3si9n)
Dale
(@dwijnand)
• Lightbend Tooling team

3. sbt by example
• https://www.scala-sbt.org/1.x/docs/sbt-by-
example.html

4. overhaul

5. overhaul

6. overhaul
• remove old parts
• update new parts
• know-how of rebuilding the parts

7. goal of sbt 1
• minimize conceptual jump from sbt 0.13

8. sbt 1 (updated parts)
• Semantic Versioning
• Binary compatible throughout 1.y.z
• Feature releases and Patch releases

9. sbt 1 (updated parts)
• Use Maven Central
• As opposed to Ivy layout hosted on Bintray behind
redirect

10. sbt 1 (updated parts)
• Use Scala 2.12 for build definition
• As opposed to Scala 2.10

11. sbt 1 (updated parts)
• Pseudo-case classes generated by Contraband
• https://www.scala-sbt.org/contraband/
• Instead of .copy(foo = 1), you write .withFoo(1)
• Generates JSON codec

12. sbt 1 (updated parts)
• Incremental compiler Zinc 1
• https://github.com/sbt/zinc
• Class-based name hashing

13. sbt 1 (updated parts)
• Library Management (LM) API
• https://github.com/sbt/librarymanagement
• Abstracts Apache Ivy so we can replace it later

14. sbt 1 (removed parts)
• sbt.Plugin
• Use sbt.AutoPlugin introduced in sbt 0.13.5

15. sbt 1 (removed parts)
• sbt 0.12 style
• the key dependency operators: <<=, <+=, <++=
• the tuple enrichments (apply and map)
• sbt.Build trait in project/Build.scala

16. sbt 1 (new parts)
• sbt server
• unified slash syntax
• more on these later

17. sbt ecosystem

18. sbt is a hub
• builds
• dependency graph, library ecosystem
• test interface
• development tasks
• plugins
• developers (users & contributors)

19. how big is the ecosystem
• 147,367 code results
• "scalaVersion" extension:sbt

20. how big is the ecosystem
• 209,745 download per month (sbt 1 on Maven Central)
• (excludes preloaded .zip, .tgz, .msi)

21. how big is the ecosystem
• 12956 downloads (in 7 days after 1.1.5 came out)

22. how big is the ecosystem
• 455 plugins (341 0.13 plugins; 224 1.0 plugins)
• 600+ packages on Bintray sbt/sbt-plugin-releases

23. migrating the plugin ecosystem
• organizing community efforts
10 days later..

24. migrating the plugins ecosystem
• 99 plugins were on sbt 1 in 2 months

25. Places to find us
• sbt 1 / Zinc meeting (every Wednesday)
• Gitter (sbt/sbt + sbt/sbt-contrib)
• Lightbend Discuss: https://
discuss.lightbend.com/c/tooling
• Stackoverflow: http://stackoverflow.com/
tags/sbt
• GitHub Issues: sbt/sbt
• Twitter: https://twitter.com/scala_sbt
• and lots of repos...

26. GitHub repos
• sbt/sbt - the build tool
• sbt/zinc
• sbt/librarymanagement
• sbt/util
• sbt/io
• sbt/website
• sbt/launcher
• sbt/sbt-launcher-package
• sbt/contraband
• sbt/sbt-houserules

27. GitHub repos
• sbt/sbt - the build tool
• sbt/zinc
• sbt/librarymanagement
• sbt/util
• sbt/io
• sbt/website
• sbt/launcher
• sbt/sbt-launcher-package
• sbt/contraband
• sbt/sbt-houserules
all repos:
• build: sbt
• PR validation: Travis CI
• Testing: ScalaTest/Specs2/ScalaCheck/scripted

28. Types of contributions
• Help adoption
• Assist other users
• At work, on Stackoverflow etc
• Contribute to documentation
• Garden the issue tracker
• Report issues
• Expand ecosystem
• Patch the core

29. Gardening the issue tracker
• Summarize discussions from other channels
• Capture problems
• Sift facts, opinions, and analysis (steps, problems,
expectations, notes)
• Reproduce the reported issues
• Triage
• Leaving breadcrumbs for contributors (previous
discussions, source links)

30. Patching the core
• Lightbend Discuss
• "Help wanted", "Good first issue"

31. Plugins that got merged to sbt
• sbt-core-next
• sbt-doge
• sbt-slash
• sbt-cross-building

32. sbt server

33. • See http://eed3si9n.com/sbt-server-reboot
sbt server reboot

34. Language Server Protocol
• created by Microsoft for VS Code
• abstracts IDE features like a web API
LSP
VS Code
Eclipse
Sublime 3
NeoVim
TypeScript
Python
sbt

35. demand for rich development environment
• Jump to error
• Code navigation
• Tab completion
• Visual debugging
• Incremental compiler
• Library management
• Test integration
• Plugin capabilities
(100+ of plugins)
Editors sbt
• LSP
• Event logging

36. a brief history of sbt server
• 'client-server split for sbt' (2013) Havoc Pennington
• A proposal to split sbt into 2 JVMs: client (cmd,
IDE, Play run etc) talks to server.
• Typesafe Activator 1.3.0 (2015) was released
using sbt-remote-control.
• 'sbt server reboot' (2016) Eugene Yokota
• 1 JVM. sbt server listens to both CLI and
network. IDEA calling compile.
• sbt 1.1.0 (2017) was released with server built-in
using Language Server Protocol.

37. • single JVM process
• implemented as a command, sort of
• JSON API to drive sbt from network
what is sbt server?

38. • IDE integration
• Distributed build
example usages

39. sbt main loop
shell prompts the user

40. sbt new "shell" command
shell prompts the user,
and listens to network

41. nc
$ nc -U /Users/foo/.sbt/1.0/server/
0845deda85cb41abcdef/sock
Content-Length: 99^M
^M
{ "jsonrpc": "2.0", "id": 1, "method":
"initialize", "params":
{ "initializationOptions": { } } }^M
...

42. input/output of common tasks
compile task

43. input/output of common tasks
• Outputs are side effects to disk and screen

44. event logging
• A way to log object (semantic logging)
• Logs are then relayed as JSON
• Decoupled from screens

45. unified slash syntax

46. sbt
• a way of describing your build
• interactive shell for development

47. sbt 0.13
• (scalacOptions in (Test, console)).value
• test:console::scalacOptions

48. sbt 1.1.x
• (Test/console/scalacOptions).value
• Test/console/scalacOptions

49. unified slash syntax
• [reference /] [Config /] [intask /] key
• foo / compile
• foo / Test / compile
• ThisBuild / organization
• foo / Compile / console / scalacOptions

50. scope delegation
• [reference /] [Config /] [intask /] key
• foo / Test / console / scalacOptions
Zero
Runtime console
Compile
Zero
Zero
ThisBuild
Zero
Zero
... ...

51. problematic areas

52. sauce dependency

53. sbt-sriracha
• adds .sourceDependency(scoptJVMRef,
scoptJVMLib)
• use -Dsbt.sourcemode=true to switch
http://eed3si9n.com/hot-source-dependencies-using-sbt-sriracha
lazy val scoptJVMRef = ProjectRef(
workspaceDirectory / "scopt", "scoptJVM")
lazy val scoptJVMLib = "com.github.scopt" %% "scopt" % "3.7.0"
lazy val root = (project in file("."))
.sourceDependency(scoptJVMRef, scoptJVMLib)
.settings(
name := "Hello world"
)

54. cross building across
Scala versions, platforms, etc

55. sbt-projectmatrix (TBA)
• adds lazy val foo = projectMatrix
lazy val core = (projectMatrix in file("core"))
.scalaVersions("2.12.6", "2.11.12")
.settings(
name := "core"
)
.jvmPlatform()
lazy val app = (projectMatrix in file("app"))
.dependsOn(core)
.scalaVersions("2.12.6")
.settings(
name := "app"
)
.jvmPlatform()
https://discuss.lightbend.com/t/spatial-representation-of-cross-
building/1277/9

56. Potential areas of contribution
• Library management (Coursier)
• Dependency locking
• Migrate code examples to compiled docs
• Look for "Help wanted" label in GitHub issues

57. Questions?

59. Lightbend Subscription