Lazy vals are not instrumented with Scala 2.12

[gslowikowski]

Simple example:

object ObjectWithLazyVal {

  lazy val lazyFoo = {
    println("foo")
    "foo"
  }

}

With Scala 2.11.8 there are two statements, with Scala 2.12.1 - zero.

This is caused by internal changes in Scala 2.12.
In Scoverage plugin there is (in tag v1.3.0, in master it's slightly simplified):

        /**
         * We can ignore lazy val defs as they are implemented by a generated defdef
         */
        case v: ValDef if v.symbol.isLazy =>
          val w = v
          tree

Scala 2.12 does not generate mentioned defs.

ModuleDef tree (viewed in debugger) for the above example object looks like this with Scala 2.11.8:

object ObjectWithLazyVal extends scala.AnyRef {
  def <init>(): ObjectWithLazyVal.type = {
    ObjectWithLazyVal.super.<init>();
    ()
  };
  lazy private[this] var lazyFoo: String = _;
  <stable> <accessor> lazy def lazyFoo: String = {
    ObjectWithLazyVal.this.lazyFoo = {
      scala.this.Predef.println("foo");
      "foo"
    };
    ObjectWithLazyVal.this.lazyFoo
  }
}

and with Scala 2.12.1:

object ObjectWithLazyVal extends scala.AnyRef {
  def <init>(): ObjectWithLazyVal.type = {
    ObjectWithLazyVal.super.<init>();
    ()
  };
  <stable> <accessor> lazy val lazyFoo: String = {
    scala.Predef.println("foo");
    "foo"
  }
}

Compiled classes look identical.

[dsilvasc]

is there a recommended workaround for this?

[dlangdon]

lost a day till I found this, and sadly the years seem to keep piling up.

[viktor-podzigun]

Hi,
@dsilvasc, @dlangdon I can share the workaround that I'm using so far:

object ObjectWithLazyVal {

  lazy val lazyFoo = createFoo()

  private def createFoo() = {
    println("foo")
    "foo"
  }
}

Not perfect, but it works. Hope it helps you as well.

[dlangdon]

@viktor-podzigun Thanks! I though about that, but I'm on the fence on applying it. As imperfect solutions go, I'd rather have better code with less accurate coverage than the opposite... even to the point of maybe just using a plain-java, line-based coverage tool.

The main issue though was debugging the problem and reaching this stage (and finding this issue). 'lazy' being a core part of the language it is not intuitive to think that is the reason. In my case this was a class that only contained an akka-http route initialization, and I was seeing the entire file not appearing within results. I blamed in order: akka-http, exclusion regexps, the file not being instrumented, sbt, etc.

[jitsumi]

Hello,
I ran into the same issue today, it seems that lazy val are included from the report.