Any kind of `.show()` on `java.nio.file.Path` causes a StackOverflowError

Simple example:

import io.kotest.assertions.show.show

println(Paths.get("a/b/c").show().value)

fails with the following error:

java.lang.StackOverflowError
	at kotlin.collections.CollectionsKt___CollectionsKt.joinTo(_Collections.kt)
	at kotlin.collections.CollectionsKt___CollectionsKt.joinToString(_Collections.kt:2330)
	at kotlin.collections.CollectionsKt___CollectionsKt.joinToString$default(_Collections.kt:2329)
	at io.kotest.assertions.show.DefaultShowKt.getCollectionSnippet(DefaultShow.kt:45)
	at io.kotest.assertions.show.DefaultShowKt.access$getCollectionSnippet(DefaultShow.kt:1)
	at io.kotest.assertions.show.DefaultShow.show(DefaultShow.kt:26)
	at io.kotest.assertions.show.DefaultShow.show(DefaultShow.kt:27)
	at io.kotest.assertions.show.ShowKt.show(Show.kt:25)
	at io.kotest.assertions.show.DefaultShowKt.recursiveRepr(DefaultShow.kt:56)
	at io.kotest.assertions.show.DefaultShowKt$getCollectionSnippet$1.invoke(DefaultShow.kt:51)
	at io.kotest.assertions.show.DefaultShowKt$getCollectionSnippet$1.invoke(DefaultShow.kt)
	at kotlin.text.StringsKt__StringBuilderKt.appendElement(StringBuilder.kt:58)
	at kotlin.collections.CollectionsKt___CollectionsKt.joinTo(_Collections.kt:2313)
	at kotlin.collections.CollectionsKt___CollectionsKt.joinToString(_Collections.kt:2330)
	at kotlin.collections.CollectionsKt___CollectionsKt.joinToString$default(_Collections.kt:2329)
	at io.kotest.assertions.show.DefaultShowKt.getCollectionSnippet(DefaultShow.kt:45)
...

This is probably caused by the fact that Path is an Iterable<Path>.

This problem makes many of the matchers working with Paths unusable, because they want to print the Path somehow, which invariably causes a StackOverflowError. For example, something like

val actual: List<Path> = ...
actual.shouldContainExactlyInAnyOrder(
    Paths.get("a/b/c"),
    Paths.get("d/e/f")
)

also fails with the StackOverflowError, because it always attempts to show the collections on the left and right sides when it returns MatcherResult.

Curiously, some other matchers (e.g. shouldContainExactly) use closures to generate their messages, so they will work in the successful case, but will then result in a stack overflow if their respective assertion fails.

Kotest 4.0.1.

[sksamuel]

I’ve investigated this and it’s because Path iterators returned Iterator<Path> so when you call show on each individual element, you get into the infinite loop. Fix applied on master and will be included in 4.0.3

[sksamuel]

4.0.6 has been released which fixes this.