mirror of https://github.com/sbt/sbt.git
72 lines
2.9 KiB
ReStructuredText
72 lines
2.9 KiB
ReStructuredText
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========================
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Advanced Command Example
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========================
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This is an advanced example showing some of the power of the new
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settings system. It shows how to temporarily modify all declared
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dependencies in the build, regardless of where they are defined. It
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directly operates on the final ``Seq[Setting[_]]`` produced from every
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setting involved in the build.
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The modifications are applied by running *canonicalize*. A *reload* or
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using *set* reverts the modifications, requiring *canonicalize* to be
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run again.
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This particular example shows how to transform all declared dependencies
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on ScalaCheck to use version 1.8. As an exercise, you might try
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transforming other dependencies, the repositories used, or the scalac
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options used. It is possible to add or remove settings as well.
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This kind of transformation is possible directly on the settings of
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Project, but it would not include settings automatically added from
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plugins or build.sbt files. What this example shows is doing it
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unconditionally on all settings in all projects in all builds, including
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external builds.
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::
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import sbt._
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import Keys._
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object Canon extends Plugin
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{
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// Registers the canonicalize command in every project
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override def settings = Seq(commands += canonicalize)
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// Define the command. This takes the existing settings (including any session settings)
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// and applies 'f' to each Setting[_]
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def canonicalize = Command.command("canonicalize") { (state: State) =>
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val extracted = Project.extract(state)
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import extracted._
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val transformed = session.mergeSettings map ( s => f(s) )
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val newStructure = Load.reapply(transformed, structure)
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Project.setProject(session, newStructure, state)
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}
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// Transforms a Setting[_].
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def f(s: Setting[_]): Setting[_] = s.key.key match {
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// transform all settings that modify libraryDependencies
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case Keys.libraryDependencies.key =>
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// hey scalac. T == Seq[ModuleID]
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s.asInstanceOf[Setting[Seq[ModuleID]]].mapInit(mapLibraryDependencies)
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// preserve other settings
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case _ => s
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}
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// This must be idempotent because it gets applied after every transformation.
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// That is, if the user does:
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// libraryDependencies += a
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// libraryDependencies += b
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// then this method will be called for Seq(a) and Seq(a,b)
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def mapLibraryDependencies(key: ScopedKey[Seq[ModuleID]], value: Seq[ModuleID]): Seq[ModuleID] =
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value map mapSingle
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// This is the fundamental transformation.
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// Here we map all declared ScalaCheck dependencies to be version 1.8
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def mapSingle(module: ModuleID): ModuleID =
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if(module.name == "scalacheck")
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module.copy(revision = "1.8")
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else
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module
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}
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