This is for Scala 2.11.1 and sbt 0.13.5.
Say I have a Scala/sbt project with the following directory structure:
root/
build.sbt
src/ ..
project/
plugins.sbt
build.properties
LolUtils.scala
and I want to use some external library in LolUtils.scala. How is this generally accomplished in sbt?
If I simply add the libs I need into build.sbt via libraryDependencies += .. then it doesn't find them and fails on the import line with not found: object ...
If I add a separate project/build.sbt, for some reason it starts failing to resolve my plugins, plus I need to manually specify the Scala version in the nested project/build.sbt, which is unnecessary duplication.
What's the best way to accomplish this?
sbt is recursive which means that it uses itself to compile a build definition, i.e. *.sbt files and *.scala files under project directory. To add extra dependencies to use them in the build definition you have to declare them in a project/build.sbt.
There is one caveat to that. You can set any scalaVersion to your project, that is in build.sbt, but you should not modify scalaVersion in the project/build.sbt as it might conflict with the version sbt itself uses (that may or may not lead to binary incompatibility for plugins).
Sbt 0.13.5 is using Scala 2.10.4, and the library you're going to use must be compatible with that particular version of Scala.
> about
[info] This is sbt 0.13.5
...
[info] sbt, sbt plugins, and build definitions are using Scala 2.10.4
Related
I am trying to understand why Adding sbt plugins in plugins.sbt in the project, works perfectly fine, but if I add the compiler plugins in that file it does not work ?
I thought any .sbt or .scala file in project, is made available for the build definition.
The only place where compiler plugins works is in the build.sbt. Hence i am confused as to why ?
In particular i am working with Kind-Projector
addCompilerPlugin("org.typelevel" %% "kind-projector" % "0.11.3" cross CrossVersion.full)
I see the following alias for the function
/** Adds `dependency` to `libraryDependencies` in the auto-compiler plugin configuration. */
def addCompilerPlugin(dependency: ModuleID): Setting[Seq[ModuleID]] =
libraryDependencies += compilerPlugin(dependency)
Hence just trying to understanding, what makes it that it can only be added to the build.sbt and not plugins.sbt in project/
Remeber sbt is recursive.
.sbt define things that are available in the current layer.
.scala files define thins that will be available in the next layer.
Adding an sbt plugin in project/bar.sbt is adding that plugin to the meta layer, as such the meta-layer that compiles the sbt you are using to compile your project adds those plugins to the next sbt layer.
So if you add a compiler plugin in project/foo.sbt then you are adding that compiler plugin to the compiler used to compile the project (meta) layer of sbt, but it will not be available in the current layer of sbt. That is the reason why compiler plugins are added in the build.sbt file, so they are added to the compiler used to compile your code.
Disclaimer: I am new to sbt and Scala so I might be missing obvious things.
My objective here is to use the Scala compiler as a library from my main project. I was initially doing that by manually placing the scala jars in a libs directory in my project and then including that dir in my classpath. Note that at the time I wasn't using sbt. Now, I want to use sbt and also download the scala sources from github, build the scala jars and then build my project. I start by creating 2 directories: myProject and myProject/project. I then create the following 4 files:
The sbt version file:
// File 1: project/build.properties
sbt.version=0.13.17
The plugins file (not relevant to this question):
// File 2: project/plugins.sbt
addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.7.0")
The build.sbt file:
// File 3: build.sbt
lazy val root = (project in file(".")).
settings(
inThisBuild(List(
organization := "me",
scalaVersion := "2.11.12",
version := "0.1.0-SNAPSHOT"
)),
name := "a name"
).dependsOn(ScalaDep)
lazy val ScalaDep = RootProject(uri("https://github.com/scala/scala.git"))
My source file:
// File 4: Test.scala
import scala.tools.nsc.MainClass
object Test extends App {
println("Hello World !")
}
If I run sbt inside myProject then sbt will download the scala sources from github and then try to compile them. The problem is that the base-directory is still myProject. This means that if the scala sbt source files refer to something that is in the scala base-directory they won't find it. For example, the scala/project/VersionUtil.scala file tries to open the scala/versions.properties file that lies in the scala base-directory.
Question: How can I set sbt to download a github repo and then build it using that project's base-directory instead of mine's (by that I mean the base-directory of myProject in the above example) ??
Hope that makes sense.
I would really appreciate any feedback on this.
Thanks in advance !
In the Scala ecosystem you usually depend on binary artifacts (libraries) that are published in Maven or Ivy repositories. Virtually all Scala projects publish binaries, including the compiler. So all you have to do is add the line below to your project settings:
libraryDependencies += "org.scala-lang" % "scala-compiler" % scalaVersion.value
dependsOn is used for dependencies between sub-projects in the same build.
For browsing sources you could use an IDE. IntelliJ IDEA can readily import Sbt projects and download/attach sources for library dependencies. Eclipse has an Sbt plugin that does the same. Ensime also, etc. Or just git clone the repository.
I'm having problems with my project which I think are due to intellij pulling in a load of scala 2.10 libraries when it created/if I reimport my project.
How can I configure it to either read the version of scala from build.sbt, or manually configure it to compile with scala 2.11.7? I'm running intellij IDEA 14 with the latest updates and it always uses scala 2.10.4.
Make sure you have your Scala Version set in your build.sbt
scalaVersion := "2.11.7"
The rest works seemlessly. Enable "Auto-Import" in IDEA when creating the project.
The 2.10 libraries are used by SBT itself. If you check the Dependencies tab for your modules, you shouldn't see them. If you do, you likely have an error in libraryDependencies in build.sbt.
I have put these in the build.sbt file under current project's root directory
scalaHome := Some(file("/Users/ddam/scala-2.10.2"))
scalaVersion := "2.10.2"
And I ran sbt using
$ sbt --version
sbt launcher version 0.12.4
But still, I am seeing both the wrong version for sbt and scala when a particular dependency cannot be resolved
[warn] Note: Some unresolved dependencies have extra attributes. Check that these dependencies exist with the requested attributes.
[warn] com.typesafe.sbteclipse:sbteclipse-plugin:2.4.0 (sbtVersion=0.12, scalaVersion=2.9.2)
Please help me.
It looks like sbteclipse requires SBT 0.13.0, and you are using version 0.12.4.
You can specify the SBT version by following the directions on this page.
Some other notes: You probably want to use Scala 2.10.3, not 2.10.2.
Also, it's strange to specify scalaHome; usually SBT will automatically fetch the needed Scala jars for you.
So to bootstrap a Scala environment, all you need to have installed are SBT and a JDK.
EDIT: (addressing comment below):
When you build code with SBT, you may actually use two different versions of Scala.
There is the version for SBT (what version of Scala the build system runs on), and the version for the code in your project (what version of Scala your code will run on).
The Scala version for SBT is determined by the SBT version you use.
If you use 0.12.4, SBT will run on Scala 2.9.3.
If you use 0.13.0, SBT will run on Scala 2.10.3.
You control the SBT version by following these instructions.
To control the version of Scala your project will run on, you can set scalaVersion in <projectRoot>/build.sbt.
So, you're getting that error because you're using SBT 0.12.4, which uses Scala 2.9.3.
SBT tries to find the sbteclipse plugin for 2.9.3, but it doesn't exist because it requires SBT 0.13.0 (=> Scala 2.10.3).
It seems you've correctly specified the use of Scala 2.10.2 for compiling your project.
sbt 0.12.4 always uses Scala 2.9.x to compile the build files (i.e. build.sbt and the stuff under project/). This means that plugins for sbt 0.12.x must also be compiled against 2.9.x, which explains what you're seeing.
sbteclipse 2.4.0 requires sbt 0.13. Try sbteclipse 2.2.0 if you want to stay on sbt 0.12.4.
emchristiansen's answer has good additional points.
Why version of SBT is playing role in name of fully qualified dependency ?
I thought it only depends on version of Scala.
Here is example.
build.sbt has scalaVersion set to 2.10.2
build.properties has sbt.version set to 0.12.1
plugins.sbt has plugin dependency "com.github.siasia" %% "xsbt-web-plugin" % "0.12.0-0.2.11.1"
If I build it I see following in the log:
[info] Resolving com.github.siasia#xsbt-web-plugin_2.9.2;0.12.0-0.2.11.1 ...
But if I change sbt.version set to 0.13.0-RC5 SBT fails to find this plugin and says in the log
[info] Resolving com.github.siasia#xsbt-web-plugin_2.10;0.12.0-0.2.11.1 ...
Why did it change scala version if it remains 2.10.2 in my config ? How to fix it ?
sbt projects are recursive, so each layer has its own settings(including scala version and classpath) (see http://www.scala-sbt.org/0.13.0/docs/Getting-Started/Full-Def.html )
sbt plugins are just regular libraries which depend on sbt, hence the plugins need to be cross-built across sbt versions (and each sbt version may require different scala version)
addSbtPlugin function takes care of that and resolves an appropriate artifact for current sbt and scala
siasia#xsbt-web-plugin is not really maintained anymore and it does not have versions for sbt 0.13, use https://github.com/JamesEarlDouglas/xsbt-web-plugin as a replacement