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Stack Overflow with complex expressions

See original GitHub issue

We occasionally get a StackOverflowError using ScalaStyle in our builds. The end of the stack is shown below, but I believe this is due to the fact that groupBy is implemented using recursion but not @tailrec.

Since the stack trace is cut off, I don’t actually have the sample code that generates the problem. However, I can generate the problem with the following valid (albeit unlikely) unit test. The Scala compiler handles this expression fine.

  "Parser" should "handle deep complex expressions" in {
    parseExpression("o.p(a" + (",a" * 2000) + ")")
  }

I’m happy to submit a PR to fix this – give me a day or two to put it together. I’ll add tests for the updated groupBy (since I’m changing it) as well as the above.

The stack trace:

   java.lang.StackOverflowError
      at scalariform.utils.Utils$$anonfun$4.apply(Utils.scala:61)
      at scalariform.utils.Utils$$anonfun$4.apply(Utils.scala:61)
      at scala.collection.immutable.List.span(List.scala:369)
      at scalariform.utils.Utils$.groupBy(Utils.scala:61)
      at scalariform.utils.Utils$.groupBy(Utils.scala:62)
      at scalariform.utils.Utils$.groupBy(Utils.scala:62)
      at scalariform.utils.Utils$.groupBy(Utils.scala:62)
      at scalariform.utils.Utils$.groupBy(Utils.scala:62)
      at scalariform.utils.Utils$.groupBy(Utils.scala:62)
      at scalariform.utils.Utils$.groupBy(Utils.scala:62)
    ... and groupBy all the way down.