Eclipse not recognizing Scala code

Question

I have Eclipse Indigo with the Scala IDE plugin. I downloaded a lift project from Maven. It builds correctly. Eclipse says it is viewing it with the Scala editor.

However, it is still giving my an error on each line because it is treat the code as Java (it gives errors for no semicolon, for the word "def" etc.) I tried cleaning the project and it still gives the errors.

Solution 1

A couple of things I would try:

1) Right-click on project, Configure > Add Scala Nature.

2) In the Scala menu, Run Setup Diagnositics... > Use recommended default settings

Solution 2

Open the Package Explorer, look at your scala source. Does the icon displays a S (for Scala), or a J (for Java)?

If you see a S, then you are likely missing the Scala Nature. As Luigi suggested, try to add the Scala Nature and see if that fixes your issue (Right-click on project, Configure > Add Scala Nature.)

Otherwise, if you see a J, the odds are that "JDT Weaving" is not enabled. That should not happen and might depend on other plugins you have installed.

What I would try if I were you is simply uninstalling all Scala IDE plugins from Eclipse ("Scala IDE for Eclipse", and also the "JDT Weaving for Scala" if you see it in the list of installed plugins). Then, reinstall Scala IDE 2.0.0-RC04. I know, it's not the ideal solution, but it's hard to tell what is going on without more information.

If that doesn't work either, please write a message in the scala-ide-user Mailing List. Make sure to provide the full list of plugins you have in your Eclipse installation. That might help us understand what is going on.

Solution 3

This problem can show up when you copy an existing java project to start a new project or use a project file generator.

One thing you can look at is your Java Build Path inside project properties. Make sure your scala source folder doesn't have an include filter like **/*.java. Make sure it is **/*.scala or remove it and your source should be detected by the scala plugin.

Solution 4

I solved the problem with compile/build errors with sbt-eclipse by

1. Right-click project
2. Scala menu -chose New Scala Installation and select version until no errors were listed

Solution 5

It may even be simpler than that, I forgot to write the package name at the top of the source file thus Eclipse neglected to see it as a Scala file.

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Comments

[Mirco Dotta]

I'm not much experienced with ScalaIDE+Maven, but I'm very surprised to hear that. I know for sure lots of folks use the Scala IDE for Eclipse with Maven, and we don't know of any such problem. What may be happening is that you regenerate the Eclipse metadata project's files, and because of that the Scala Nature is no longer added to your project. Adding the Scala Nature is very easy, simply right-click on project, Configure > Add Scala Nature. You may also be interested in m2eclipse-scala (github.com/sonatype/m2eclipse-scala).

[jamie]

I'll check that out, Mirco. Thanks.

[Mirco Dotta]

Great! Let us know how it goes, we definitely need help to improve the User Documentation with respect to Scala IDE+Maven ;)

[jhclark]

This caused the "red screen of death" (red squiggly lines everywhere for me. I believe it was because I edited my eclipse.ini file to increase the heap size (as recommended by the Scala plugin on startup) then restarted eclipse -- Then the setup diagnostics never re-ran, causing the Scala plugin not to never be setup correctly.

[Lachlan]

One thing that tripped me up - you have to be in the Scala Perspective for the Scala Nature to be available.

[Aleksandr Panzin]

Had the same problem and only after adding included items the errors went away.

[VasiliNovikov]

I think this answer was a strange way to say the problem was fixed by doing the described steps.

[Necrototem]

This also solved my issues, except I had no "source folders" listed at all. Creating a new folder, moving my source files into it, and then adding it as a source folder from the Java Build Path menu fixed my problem.

[Roy Shmuli]

It's happens any time when I switch brunches (git), Do you know how to remove it forever?

[user3030851]

Lifesaver. In my case the scala code was shown as scala in the package explorer and as java in the editor. The editor was acting insane, autocompletion not working, imports not working. After removing the java filter form the .classpath everything is back to normal.