Scala 'fromFile' weirdness?

Question

I can't understand why two bits of code that are meant to do exactly the same thing, do different things in Scala.

First example:

scala> val ggg = Source.fromFile("/somefile");
ggg: scala.io.BufferedSource = non-empty iterator

scala> ggg.getLines();
res67: Iterator[String] = empty iterator

Second example:

scala> Source.fromFile("/somefile").getLines();
res68: Iterator[String] = non-empty iterator

Aren't they meant to do the same thing, or am I missing something?

Answer 1

This seems to be a quirk (bug?) with BufferedSource.toString. Observe:

// no problem
scala> { val x = Source.fromFile("foo.txt"); x.getLines() }
res10: Iterator[String] = non-empty iterator

// ahh, calling toString somehow emptied our iterator
scala> { val x = Source.fromFile("foo.txt"); println(x.toString); x.getLines() }
non-empty iterator
res11: Iterator[String] = empty iterator

To show the value of the expression, the REPL needs to call BufferedSource.toString, and this has the side effect of emptying the iterator.

Answer 2

Looks like this bug: SI-4662.

Apparently fixed in trunk Changeset 25212, but not in 2.9.1 as far as I can see.

In the bug notes it's mentioned that it probably manifests itself only in the REPL, not in "real" code.