Map.values.map is not strict in Scala 2.13

[ijuma]

I am not sure if this is intentional, but I didn't see any mention of it in the migration notes. mutable.Map.values.map is not strict in 2.13 which can cause side-effects to be executed multiple times when compared to 2.12 and older.

A simple example follows with 2.12.8 and then 2.13.0:

Welcome to Scala 2.12.8 (OpenJDK 64-Bit Server VM, Java 11.0.2).
Type in expressions for evaluation. Or try :help.
scala> scala.collection.mutable.Map(1 -> "1", 2 -> "2")
res0: scala.collection.mutable.Map[Int,String] = Map(2 -> 2, 1 -> 1)

scala> var iterationCounter = 0
iterationCounter: Int = 0

scala> res0.values.map { v => iterationCounter += 1; v }
res1: Iterable[String] = List(2, 1)

scala> res1.toSeq
res2: Seq[String] = List(2, 1)

scala> iterationCounter
res3: Int = 2

scala> res1.toSeq
res4: Seq[String] = List(2, 1)

scala> iterationCounter
res5: Int = 2

scala> scala.collection.mutable.Map(1 -> "1", 2 -> "2")
res0: scala.collection.mutable.Map[Int,String] = HashMap(1 -> 1, 2 -> 2)

Welcome to Scala 2.13.0 (OpenJDK 64-Bit Server VM, Java 11.0.2).
Type in expressions for evaluation. Or try :help.

scala> var iterationCounter = 0
iterationCounter: Int = 0

scala> res0.values.map { v => iterationCounter += 1; v }
res1: Iterable[String] = View()

scala> res1.toSeq
res2: Seq[String] = List(1, 2)

scala> iterationCounter
res3: Int = 2

scala> res1.toSeq
res4: Seq[String] = List(1, 2)

scala> iterationCounter
res5: Int = 4

[NthPortal]

is there a reason for Map#values not returning View rather than Iterable?

[julienrf]

Not that I know. It should return a strict Iterable