scala-ide / scala-refactoring   0.8.0

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A library providing automated refactoring support for Scala.

Scala versions: 2.11 2.10

The Scala Refactoring Library

The Scala Refactoring Library implements IDE independent refactoring support for Scala. It is currently used by both ENSIME and ScalaIDE and supports Scala-2.10 and Scala-2.11.

Information for Contributors

Help Needed

We are always looking for helping hands. As you may have already found out, there are quite a few bugs to work on. Pull requests are usually reviewed and merged quickly, and we try to help new contributors wherever we can. We are currently focusing our efforts on

  • Rename
  • Organize Imports
  • Add Import
  • Move Class

All other refactorings, like

  • Extract Method
  • Extract Value
  • Extract Trait
  • Inline Local
  • Merge Parameter Lists
  • Split Parameter Lists
  • Change Parameter Order

are effectively unmaintained. If you are particularly fond of an operation from this list, this might be a very good place to start contributing!

Overall Architecture

Refactorings are implemented on top of ASTs from the Scala Presentation Compiler. If you plan to work on the library, you should definitely take a look at Mirko Stockers Master Theses. Although somewhat outdated, this document is very helpful for understanding the inner workings of the library. Another thing to look at is the presentation about the Refactoring Library given by @mlangc at ScalaSphere. The slides are available here.


All changes to the library are expected to be thoroughly covered by unit tests, unless there is a very good reason for violating this rule. Often however, you also want to see the effect of your changes in an interactive environment. If you are using ScalaIDE Nightly Builds, there are two ways to run the IDE with your custom modifications, both with their own drawbacks and advantages:

  • You can run ScalaIDE from within Eclipse, as outlined here. The Equinox Weaving Launcher will automatically pick up the local version of the Refactoring Library, if the library is properly configured as an Eclipse project.

    • Advantages:

      • Fast turnaround
      • Works even if your changes break binary compatibility
      • The only option if the IDE and the Refactoring Library are modified together
    • Disadvantages:

      • Not suitable if you want to see the effect of your changes in a production environment
  • You can patch your ScalaIDE Nightly installation with a local build of the refactoring library, generated with $ sbt package. Take a look at patch-ide.bash to see how this is done.

    • Advantages:

      • Perfect for testing the effects of your changes in a production environment
    • Disadvantages:

      • Slow turnaround
      • Works only if binary compatibility is maintained
      • Might break your Eclipse installation if you aren't careful


Parsing Scala Source Code

Unfortunately the typechecked ASTs the library gets from the Scala Presentation Compiler don't always provide enough information to properly perform refactorings. In these cases the library has to extract the missing information from the source code under consideration. Often this is more tricky than you might initially think. Using the APIs centered around SourceWithMarker should make your life a lot easier in these cases.


Make sure to switch to DebugTracing when debugging the library. Sometimes it is useful to redirect tracing output to a file. This can be done by setting the system property scala.refactoring.traceFile.


Use $ sbt package to build the library for Scala-2.11, or $ sbt +package to build it both for Scala-2.11 and Scala-2.10.


In order to publish sbt is used. The project is cross compiled against Scala 2.10 and 2.11. To test a release run sbt and type:

> + publishLocalSigned

If everything looks good the release can be uploaded:

> + publishSigned

For the upload the file ~/.m2/credentials is needed. It should contain:

realm=Sonatype Nexus Repository Manager

where USERNAME and PASSWORD are the ones from the Sonatype account, which has the necessary permissions to do a publish.


The project is licensed under the Scala license, see the LICENSE file for details.