SBT Talk at Bay Area Scala Enthusiasts' Meetup (10/10/2011 @ Foursquare SF)

1. SBT <<= (Build) { FTW }
@indrajitr

2. SBT
• Build tool on Scala for building Scala-Java projects
• Compliant with Maven's convention (mostly)
• Basics done right
• Easy to set up for simple projects (intrusive)
• Shares a *lot* with Scala
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

3. Build Definitions
• Simple: Quick DSL
• Diabolical: Scala code (with embedded DSL)
• And the shell rocks
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

4. Build Definitions
<base>/*.sbt
<base>/project/*.scala
<base>/project/plugins.sbt
<base>/project/plugins/*.(scala|sbt)
~/.sbt/plugins/*.(scala|sbt)
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

5. build.sbt
organization := "net.liftweb"
name := "lift-demo"
version := "1.0"
scalaVersion := "2.9.1"
libraryDependencies ++=
Seq("net.liftweb" %% "lift-webkit" % "2.4-M4",
"org.eclipse.jetty" % "jetty-webapp" % "7.3.0.v20110203" % "jetty")
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

6. project/build.scala
import sbt._
object LiftBuild extends Build {
lazy val projects: Seq[ProjectReference] = Seq(common, actor, json)
lazy val framework = Project("lift-framework", file(".")).aggregate(projects)
lazy val common = Project(“lift-common”, file(“core/common”)).settings(/*...*/)
lazy val actor = Project(“lift-actor”, file(“core/actor”)).dependsOn(common).settings(/*...*/)
lazy val json = Project("lift-json", file("core/json")) dependsOn(common % "test")
//lazy val foo = Project("lift-foo", file("core/foo"), delegates = common :: Nil)
}
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

7. The Expression
Reminder:
Statement ≠ Expression
Statement:
val foo = bar + baz
Expression:
bar + baz
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

8. The Expression
The expression:
organization <<= organization or normalizedName.identity
Is a: Project.Setting[S]
And <<= is thus:
final def <<= (app: Initialize[S]): Setting[S]
for: InputKey, SettingsKey
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

9. The Emojis
The ONE
<<=
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

10. The Emojis
And the rest
:= += ++= <+= <++= ~=
• Initialize ( := )
• Append ( += ++= <+= <++= )
• Update ( ~= )
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

11. Scoped Keys
sealed trait Key[T] extends Scoped
final class SettingKey[T] extends Key[T] with ScopedSetting[T]
final class TaskKey[T] extends Key[T] with ScopedTask[T]
final class InputKey[T] extends Key[InputTask[T]] with ScopedInput[T]
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

12. Examples
name := "lift-demo"
name ~= formalize
resolvers in GlobalScope += JavaNet2Repository
scalacOptions ++= Seq("-encoding", "UTF-8")
resolvers <++= isSnapshot { s => if (s) Seq(ScalaToolsSnapshots) else Nil }
inceptionYear <<= inceptionYear ?? Some(2011)
organization <<= organization or normalizedName.identity
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

13. Examples
libraryDependencies <<= (libraryDependencies, scalaVersion) apply { (ld, sv) =>
ld :+ scalap(sv) })
libraryDependencies <+= (scalaVersion)(scalap)
libraryDependencies <+= scalaVersion apply scalap
scalacOptions /*in GlobalScope*/ in doc <++= (name in doc, version in doc) map
(Seq("-doc-title", _, "-doc-version", _))
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

14. Settings are Scoped!
def in(s: Scope): Result // ScopedSetting, ScopedTask, ScopedInput
def in(p: Reference): Result
def in(t: Scoped): Result
def in(c: ConfigKey): Result
def in(c: ConfigKey, t: Scoped): Result
def in(p: Reference, c: ConfigKey): Result
def in(p: Reference, t: Scoped): Result
def in(p: Reference, c: ConfigKey, t: Scoped): Result
def in(p: ScopeAxis[Reference], c: ScopeAxis[ConfigKey], t: ScopeAxis[AttributeKey[_]]): Result
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

15. Miscellaneous
MOAR Emojis (in shell)!
~ + ++ ; ! < -
Plugin, State, Life, Universe and everything else
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

16. Lost?
Befriend ‘em
• Defaults.scala
• Keys.scala
• IDE
Bay Area Scala Enthusiasts Meeting #42 (10-10-11)

17. Exercise

18. Questions?