SBT Made Simple

SBT Made Simple
@囚千任 - http://afoo.me
Monday, September 9, 13

Immutability

Setting
• A Build File is just a sequence of Settings
• A Setting is just a transformation to key-
value pairs
• A Transformation to some key-value pair is
immutable

State Transition
• Project State is volatile
• state transition is immutable

Composition

Task
• dependency model to composition model
• task composition to form bigger granularity
unit

InputTask
• Task with input
• input validation and completion support
with parser
• parser combinator is a form of composition

Command
• Special InputTask
• accept Project state and settings as input
• project state is driven by a composition of
command execution

Modularity

Configuration
• Ivy concept similar to Maven’s Scope
• Predefined or custom Configurations setup
Modularity boundary

Project
• project is another level of modularity
• multiple project build definitions have their
specific configuration

Plugins
• SBT plugin mechanism is another
modularity strategy
• enhance reusability too.

Consistency
One Rule To Rule Them All

Same Effect?
name := {
“hello” + “sbt”
}
sbt := {
}

Not Really!
name := {
}
sbt := {
}
=> Setting[String]
=> Setting[Task[String]]

Key is the key
val name = settingKey[String](“desc.”)
name := {
}
val sbt = taskKey[String](“task desc”)
sbt := {
}
=> Setting[String]
=> Setting[Task[String]]

Key is the key
• SettingKey[T]
• TaskKey[T]
• InputKey[T]

Demo Time~

SBT Made Simple

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