*Wiki Maintenance Note:* This page has been *mostly* replaced by
[[Getting Started Full Def]] and other pages. See the note at the top of
[[Full Configuration]] for details. If we can establish (or cause to be
true) that everything in here is covered elsewhere, this page can be
empty except for links to the new pages.

There are two types of file for configuring a build: a `build.sbt`
file in you project root directory, or a `Build.scala` file in your
`project/` directory. The former is often referred to as a "light",
"quick" or "basic" configuration and the latter is often referred to as
"full" configuration. This page is about "full" configuration.

Naming the Scala build file
===========================

`Build.scala` is the typical name for this build file but in reality
it can be called anything that ends with `.scala` as it is a standard
Scala source file and sbt will detect and use it regardless of its name.

Overview of what goes in the file
=================================

The most basic form of this file defines one object which extends
`sbt.Build` e.g.:

::

    import sbt._

    object AnyName extends Build {
        
        val anyName = Project("anyname", file("."))
        
        // Declarations go here
    }

There needs to be at least one `sbt.Project` defined and in this case
we are giving it an arbitrary name and saying that it can be found in
the root of this project. In other words we are saying that this is a
build file to build the current project.

The declarations define any number of objects which can be used by sbt
to determine what to build and how to build it.

Most of the time you are not telling sbt what to do, you are simply
declaring the dependencies of your project and the particular settings
you require. sbt then uses this information to determine how to carry
out the tasks you give it when you interact with sbt on the command
line. For this reason the order of declarations tends to be unimportant.

When you define something and assign it to a val the name of the val is
often irrelevant. By defining it and making it part of an object, sbt
can then interrogate it and extract the information it requires. So, for
example, the line:

::

    val apachenet = "commons-net" % "commons-net" % "2.0"

defines a dependency and assigns it to the val `apachenet` but, unless
you refer to that val again in the build file, the name of it is of no
significance to sbt. sbt simply sees that the dependency object exists
and uses it when it needs it.

Combining "light" and "full" configuration files
================================================

It is worth noting at this stage that you can have both a `build.sbt`
file and a `Build.scala` file for the same project. If you do this,
sbt will append the configurations in `build.sbt` to those in the
`Build.scala` file. In fact you can also have multiple ".sbt" files in
your root directory and they are all appended together.

A simple example comparing a "light" and "full" configuration of the same project
=================================================================================

Here is a short "light" `build.sbt` file which defines a build project
with a single test dependency on "scalacheck":

::

    name := "My Project"

    version := "1.0"

    organization := "org.myproject"

    scalaVersion := "2.9.0-1"

    libraryDependencies += "org.scalatest" % "scalatest_2.9.0" % "1.4.1" % "test"

Here is an equivalent "full" `Build.scala` file which defines exactly
the same thing:

::

    import sbt._
    import Keys._

    object MyProjectBuild extends Build {

      val mySettings = Defaults.defaultSettings ++ Seq(
          name := "My Project",
          version := "1.0",
          organization := "org.myproject",
          scalaVersion := "2.9.0-1",
          libraryDependencies += "org.scalatest" % "scalatest_2.9.0" % "1.4.1" % "test"
      )

      val myProject = Project("MyProject", file("."), settings = mySettings)

    }

Note that we have to explicitly declare the build and project and we
have to explicitly append our settings to the default settings. All of
this work is done for us when we use a "light" build file.

To understand what is really going on you may find it helpful to see
this `Build.scala` without the imports and associated implicit
conversions:

::

    object MyProjectBuild extends sbt.Build {

      val mySettings = sbt.Defaults.defaultSettings ++ scala.Seq(
          sbt.Keys.name := "My Project",
          sbt.Keys.version := "1.0",
          sbt.Keys.organization := "org.myproject",
          sbt.Keys.scalaVersion := "2.9.0-1",
          sbt.Keys.libraryDependencies += sbt.toGroupID("org.scalatest").%("scalatest_2.9.0").%("1.4.1").%("test")
      )

      val myProject = sbt.Project("MyProject", new java.io.File("."), settings = mySettings)

    } 

