At work and at home I use Scala a lot recently. We are using Eclipse as IDE and ScalaTest 2.0 for testing.
Whenever I run a unit test, I get this message:
WARNING: -p has been deprecated and will be reused for a
different (but still very cool) purpose in ScalaTest 2.0.
Please change all uses of -p to -R.
My question is two-fold:
Why is this message appearing? I already have ScalaTest 2.0, so what is it trying to tell me?
Is it possible to get rid of this warning? Our policy is to keep code warning-free, as everyone should try to do. I could not find any information relating to this warning online or on StackOverflow.
For completeness, a code sample:
import org.scalatest.FunSuite
class WarningSpec extends FunSuite {
test("See if this gives a warning") {
assert(true)
}
}
That is likely an unfortunate case of the ScalaTest Eclipse plugin itself using the deprecated Runner command -p to set the run path when running tests. We'll try to reproduce that, and if that's the case, and fix it by using -R instead and update the plugin.
Related
After switching to Java 11, sbt tests started to fail with the exception "No configuration setting found for key 'akka'". We are using sbt assembly plugin on the project but since the tests are run not inside jar but using sbt <module_name>/test, looks like there are some issues with building test resources/paths.
List of things I did:
Added concat MergeStrategy for 'reference.conf' file. Jar that is assembled has all files inside and there are no issues with that, so it is only a test step issue.
Checked class path for tests using 'export <module_name>/test:fullClasspath' in sbt before and after migrating to Java 11. They are the same.
Everything else except of a test where I create actor system works good.
Code that creates actor system:
object MyObjectTest extends AsyncFunSuite {
private implicit val system: ActorSystem = ActorSystem("MyActorSystem")
private implicit val ex: ExecutionContext = system.dispatcher
}
At the moment I do not have any ideas what should I check next, so any suggestions would be appreciated.
P.S. running tests inside IDEA works good, but we have CI/CD job that runs tests using sbt test command.
I guess there are some issues when you are using sbt + Java 11. I tried to reproduce this error using a small project with the same configuration but was not been able to do it. However, the issue was fixed using the following option in sbt:
Test / fork := true
According to sbt documentation, this property creates a separate JVM for running all tests. I think all configurations have been set up correctly for another JVM.
Hope this answer will help someone in future.
I am learning Scala and I am using typesafe activator to run the programs. I have my first program in the below path <downloads>\typesafe-activator-1.3.7\activator-dist-1.3.7\simple scala project\scala-2.11\Simple_scala_project.scala
Below is the program content
object Simple_scala_project {
def main (args:String): Unit =
{ println("My first scala program") }
}
when I am running the below command in the command line I am getting the error
scala -cp <downloads>\typesafe-activator-1.3.7\activator-dist-1.3.7\simple scala project\scala-2.11 Simple_scala_project
:1: error: ';' expected but double literal found.
Please help me in this.
I noted a similar error when I inadvertently placed a line including "sbt.version=1.3.13" (in my case) in the wrong file. I realize now that it should have gone into a folder insider my overall project folder called "project", inside a file called "build.properties" (instead of in "build.sbt").
The take-away from this is that I don't think you experienced a compiler error at all, but an error owing to some files in the project setup. Better SBT documentation may be found here.
It's absolutely true that SBT isn't needed for very simple examples, and indeed offends the sensibilities of ones volunteering to learn a new language (soon to be improved, Scala 3.x, not a hundred other extraneous technologies. I find IntelliJ Idea Community to be a boost, here, since its Scala support is first-rate, and will create simple example projects for you in a variety of ways Installing Scala / Installing Scala plugin for Idea.
I have my very first Scala program, which is as simple as:
object HelloWorld{
def main(args: Array[String]){
println("Hello world!")
}
}
I then try to compile it like so:
$ scalac HelloWorld.scala
And it compiles without any error messages. When however I try to run it like so:
$ scala HelloWorld
I get an error message:
No such file or class on classpath: HelloWorld
To implement this, I followed this tutorial and to solve the emerged error, I followed this suggestion. However,
$ scala objects.HelloWorld
also does not work. I know many people will now start heavily voting down my question and asking questions - have you ever tried to read some books on it (Yes, I did. I've read Horstman book for beginners, but it does not contain any information on compiling programs under Ubuntu). Still, I hope someone could help.
(This was a comment before, and I rephrased it to a response.)
You've done everything right, except for the last step: Use the java command instead of the scala command.
scala is the Scala REPL. No separate run command is required for Scala code, because it compiles to regular Java bytecode.
So try: java HelloWorld
For more complex programs that make use of the Scala library however, you need to include the Scala runtime library in the classpath. So, on the long run, it is beneficiary to use a tool like SBT, as pointed out by #roterl in the comments.
The answer saying that the scala command is just for the REPL is incorrect. You can see from the man page entry for scala (http://www.scala-lang.org/files/archive/nightly/docs-2.10.2/manual/html/scala.html) that it is intended to be used in the same way as the java command with the added flexibility that it will run the REPL, scripts, or compiled applications.
As some of the comments have indicated, this is almost certainly a path issue, which means that it requires more information to diagnose. One thing you can check is whether the scalac command produced a .class file in your current directory. If that is in the directory where you are running scala then the comments about needing . in your classpath are almost certainly correct.
I'm using Eclipse ScalaIDE and for some reason I'm not able to
import scala.io.StdIn
I'm getting a red squiggly that tells me:
object StdIn is not a member of package io
And I'm seeing that it's not in that scala.io jar file. The ScalaDoc, however says it should be there. I've tried both scala 2.10.4 and 2.11.5. I've used the Eclipse ScalaIDE to create the scala project and I've also created an sbt eclipse project directly using the scalasbt.plugin which I use all the time to manage ScalaIDE dependencies.
sbt "eclipse with-source=true"
Neither way is getting it.
I'm currently taking the Coursera Reactive Programming course and an assignment file has this import. I'm able do compile the project with sbt directly, but Eclipse ScalaIDE is not doing the job. Any clues? There may be good reason why not to use scala.io.StdIn, but my question is why can I not get it to import in the ScalaIDE?
thank you
scala.io.StdIn is new in scala 2.11.x and does not exist in previous versions.
The problem you are likely encountering is that ScalaIDE is not picking up the scala version you are specifying. Since you say that you tried it with 2.10.4, it probably still has that cached or set somewhere and it's failing because it cannot find the specified class.
I am trying to develop an application using java opencv 3.0.0-beta using scala.
I am getting a runtime error:
java.lang.UnsatisfiedLinkError: java.lang.UnsatisfiedLinkError: org.opencv.imgcodecs.Imgcodecs.imread_1(Ljava/lang/String;)J
While researching the cause i have created the following simple application the exhibits similar behaviour:
import reflect._
import org.opencv.core.Core
import org.opencv.core.Mat
import org.opencv.core.CvType
import org.opencv.imgcodecs.Imgcodecs
object main extends Application {
System.loadLibrary(Core.NATIVE_LIBRARY_NAME)
val what = "something.png"
val mat = Imgcodecs.imread(what)
Imgcodecs.imwrite("something_else.png", mat)
}
The major difference is that, if run as "sbt run" it performs as expected. if the appropriate lines are removed from the above the code fails in REPL.
I suspect that this issue is related to the original issue, but have no proof.
If i look at the memory map of the JVM in both cases i have the expected libs loaded.
If the code is inspected i find no definition of org.opencv.imgcodecs.Imgcodecs.imread_1
I am quite lost as to where to go next in diagnosing this issue.
Is there anyone who has come across this issue?
Thanks
i haven't used openCV3.0 yet, as it has major changes and breaks opencv 2.4.x code , are you supplying the library path to
sbt run
add
javaOptions in run += "-Djava.library.path=lib/opencv/"
to your build.sbt file or pass on cmd line
sbt run -Djava.library.path=lib/opencv/
opencv folder should have your files that gets generated along with your jar file
i have java bindins for 2.4.9 , 2.4.10 and 3.0.0 for java 7 and 8 in this git repo if you need them
git#gitlab.com:opencv/java_lib.git