I started to learn Scala and almost in every tutorial I see a build.sbt file which describes project settings. But now I have installed giter8 and created a project from template. And generated project from template missed build.sbt file, but it have build.scala (which seems used for same purposes, but it is more flexible).
So what is the difference between build.sbt and build.scala?
Which is more preferred and why?
To give a brief example, this build.sbt:
name := "hello"
version := "1.0"
is a shorthand notation roughly equivalent to this project/Build.scala:
import sbt._
import Keys._
object Build extends Build {
lazy val root = Project(id = "root", base = file(".")).settings(
name := "hello",
version := "1.0"
)
}
The .sbt file can also include vals, lazy vals, and defs (but not objects and classes).
See the SBT document called ".scala build definition", particularly the section "Relating build.sbt to Build.scala".
Consider a .scala build definition if you're doing something complicated where you want the full expressiveness of Scala.
Update July 2016 (3 years later)
Build.scala is officially deprecated in sbt 0.13.12
The Build trait is deprecated in favor of the .sbt format
PR 2530 implements that deprecation.
"Appendix: .scala build definition" has been updated.
When .sbts are being compiled, they are before that sort of merged with the .scala files inside project directory. They can't be used in recursive tasks, that is, you can't customize sbt from sbt, for example. For more detailed information, consider reading related section is sbt documentation: http://www.scala-sbt.org/release/docs/Getting-Started/Basic-Def.html#sbt-vs-scala-definition
Related
I am trying to create a local library which contains a class
myproject.scala:
object test {
def info(message: String): Unit = println(s"INFO: $message")
}
build.sbt:
name := "MyProject"
version := "0.1"
organization := "MyCorp"
scalaVersion := "2.11.0"
sbtVersion := "0.13"
I ran sbt clean compile publishLocal and I see the jar in my local ivy2 directory. What I'm unsure about is how to now use that library in another project.
do I added libraryDependencies += "MyCorp"%"myproject_2.11"%"0.1"
to the second project's sbt, and I see it in the classPath when I print it out in the repl. The problem is when I try
import MyCorp.myproject
I get an error not found. I'm sure I'm missing something simple, but it's driving me nuts.
I ran sbt clean compile and I see the jar in my local ivy2 directory.
That's weird. sbt clean compile does not publish the artifact in the local repository. (Have you copied it manually there?) That should have been done with publishLocal command and the artifact should become available at {path_to_.ivy2}/local/MyCorp/MyProject/0.1/jars/MyProject.jar.
Now in your second project, it can be added as
libraryDependencies += "MyCorp" % "MyProject" % "0.1"
// or in libraryDependencies ++= Seq(...)
Please notice that the _2.11 suffix that you have used in the name depends on how the first project was built, whether its build was differentiated by Scala versions. If it was, the suffix would be usually present in the artifact .jar file name. And it is preferable to avoid including the suffix in the library dependency declaration, but rather use %% for built-in support.
After checking it, also try to restart the SBT CLI, because unfortunately sometimes changes in build.sbt are not taken into account on-the-fly.
Update
I assume its mycorp.myproject.test , but I tried every possible combination. #Brian
Following the comments, I think that there still should be something misconfigured in the project and/or missing in the description.
Assuming there is a file {path/to/project}/src/main/scala/mycorp/myproject/Test.scala, with the following contents:
package mycorp.myproject
object Test {
def info(message: String): Unit = println(s"INFO: $message")
}
When the artifact is published, the .jar file should contain the folders mycorp/myproject with Test.class and Test$.class files.
After adding the .jar to the dependencies of the second project, importing Test into another class should look like:
package mycorp.myproject2
import mycorp.myproject.Test
object AnotherTest extends App {
Test.info("hello")
}
I hope this helps.
End-of-update
This is a problem that is really getting on my nerves. I'm writing proofs for the Welder proof assistant. I was doing so without the help of an IDE and following an SBT-based building approach. This is the build file:
name := "proofs"
scalaVersion := "2.11.8"
lazy val welder = RootProject(uri("git://github.com/epfl-lara/welder.git#2b9dd10a7a751777cc9cda543ce888294113c0b1"))
lazy val root = (project in file(".")).dependsOn(welder)
I tried to bring my project into an Intellij Idea project. However, while doing so, the IDE won't recognize the imports of the external library:
import inox._
How can I solve this issue?
Edit
I stress that the compile errors are produced in the files from Welder
Here is the welder project/Build.scala file
import sbt._
object WelderBuild extends Build {
lazy val root = Project("root", file(".")) dependsOn(inoxProject)
lazy val inoxProject = RootProject(uri("git://github.com/epfl-lara/inox.git#53ea4533a957050bd6a968d5a340890bd54998a5"))
}
See my answer to your other question and the issue on the Scala plugin issue tracker.
Renaming the modules and manually adding a dependency from the welder-root to the inox-root module will solve the compile path issue, but the build will still fail because one of the project uses source generators, which are not supported in IDEA directly.
Instead, enable the "use sbt for build and import" option in the sbt preferences:
Using SBT 0.13.13, our build definition is inherited from an older project. Currently there are a build.sbt and some project/*.scala files. These scala files follow the same pattern. Here is an example:
import sbt._
import sbt.Keys._
object Docs {
lazy val docTask = TaskKey[Unit]("docPackage", "Generate Scaladoc")
lazy val settings = Seq(
docTask := {
val docs = (doc in Compile).value
IO.copyDirectory(docs, new java.io.File("src/main/resources/myapp-scaladoc"), overwrite = true)
},
docTask := (docTask.dependsOn(doc in Compile)).value
)
}
Appendix: .scala build definition says
In the previous versions of sbt, .scala was the only way to create
multi-project build definition
Question: I suppose this mean the use of separate project/*.scala files is discouraged. If so, is it OK to move the code of these *.scala file and put them all in build.sbt?
There is little functional difference between having code in project/ and code in build.sbt.
The advantage to putting code in a .scala file in project/ is that all symbols in it are imported into the namespace of all build.sbt files in all subprojects of your build. This means that helper methods, constants, plugins, or other Scala code can live in a single location, but be called from anywhere.
Ultimately, whether to use this features comes down to whether you want shared items configured in a single location, or in multiple locations.
If you prefer to have your project settings configured entirely in separate build.sbt files in their subproject directories, putting shared settings in the project/ folder is the way to do that.
If you're OK with having shared settings configured in the root build.sbt file (or if you don't use any subproject build.sbt files), you can consolidate all of your shared configuration into it.
I'd like to know how to convert a regular scala project into an sbt project. I've tried manually creating an sbt file on the root directory, correctly implemented, but Intellij still doesn't recognize this as a sbt project, i.e, it won't show me in the "View -> Tool Windows" the "SBT" option.
How should I go about this? What I'm actually attempting to do is to create an empty project with multiple (independent) modules.
From what I've gathered there seems to be no way to add a module directly with sbt support, am I right?
Thanks
Here is an example of a multi-project build. The root project "aggregates" them all in case you want to compile them all together or package them all together, etc. The "coreLibrary" project depends on the code of "coreA" and "coreB".
import sbt.Keys._
import sbt._
name := "MultiProject"
lazy val root = project.in(file(".")).aggregate(coreA, coreB, coreLibrary)
lazy val coreA = Project("CoreA", file("core-a")).settings(
organization := "org.me",
version := "0.1-SNAPSHOT"
)
lazy val coreB = Project("CoreB", file("core-b")).settings(
organization := "org.me",
libraryDependencies += "org.apache.kafka" %% "kafka" % "0.8.2-beta",
version := "0.3-SNAPSHOT"
)
lazy val coreLibrary = Project("UberCore", file("core-main")).dependsOn(coreA, coreB).settings(
organization := "org.me",
version := "0.2-SNAPSHOT"
)
You can (for example) compile each project from the command line:
>sbt CoreB/compile
Or you can do this interactively:
>sbt
>project CoreB
>compile
I recommend you to use a single multiple-module SBT project. sbt is a great build tool for scala, you can do a lot of things with sbt, including checking out from the repository one module and built it.
sbt
projects
project <helloProject>
Actually, this feature allows multiple people to work on the same project in parallel. Please take a look at this: http://www.scala-sbt.org/0.13.5/docs/Getting-Started/Multi-Project.html.
I am new to sbt (using sbt.version=0.13.5) created multiproject build definition as following (build.sbt):
name := "hello-app"
version in ThisBuild := "1.0.0"
organization in ThisBuild := "com.jaksky.hello"
scalaVersion := "2.10.4"
ideaExcludeFolders ++= Seq (
".idea",
".idea_modules"
)
lazy val common = (
Project("common",file("common"))
)
lazy val be_services = (
Project("be-services",file("be-services"))
dependsOn(common)
)
My expectation was that sbt will generate directory layout for the projects (based on the documentation). What happened was that just only top directories were generated (common and be-services) with target folder in it.
I tried it in batch mode sbt compile or in interactive mode - none has generated expected folder structures e.g. /src/{main, test}/{scala, java, resources}.
So either my expectations are wrong or there is some problem in my definition or some speciall setting, plugin etc.
Could some more experienced user clarify that, please?
Thanks
As #vptheron correctly points out, sbt does not generate any project directories, with the exception of the target directory when it produces compiled class files.
You might find that functionality in plugins, e.g. np. Also if you use an IDE such as IntelliJ IDEA, creating a new sbt-based project will initialize a couple of directories (such as src).