==~ causes PatternSyntaxException when used in a block

[kdebski85]

Describe the bug

Spock version: 2.3

    def "should compare lists"() {
        given:
        Consumer<Integer> c = { [] ==~ [] }
        c.accept(1)

        expect:
        true
    }

It fails with java.util.regex.PatternSyntaxException: Unclosed character class near index 1

To Reproduce

  def "should compare lists"() {
        given:
        Consumer<Integer> c = { [] ==~ [] }
        c.accept(1)

        expect:
        true
    }

Expected behavior

==~ spock operator should work in blocks

Alternatively, https://spockframework.org/spock/docs/2.3/utilities.html#_strict_match should state clearly this limitation.

Actual behavior

It fails with java.util.regex.PatternSyntaxException: Unclosed character class near index 1

Java version

21.0.1

Buildtool version

Gradle 8.14.2

What operating system are you using

Mac

Dependencies

none

Additional context

No response

[Vampire]

That's just the normal "it isn't treated as condition" limitation.

For most parts only top-level expression statements are treated as conditions which is documented at https://spockframework.org/spock/docs/2.3/all_in_one.html#_implicit_and_explicit_conditions.

You can reproduce even easier with

def "should compare lists"() {
  expect:
    if (true) [] ==~ []
}

If it is not considered a condition, the operator has its original Groovy meaning.

If you make it an explicit condition by moving the expression to top-level, or make it an explicit condition by adding assert, the special handling of the operator kicks in and it works and also throws as expected if the check fails.

[kdebski85]

@Vampire Thank you for the explanation.

However, I think it is a documentation issue. I cannot see this limitation mentioned at https://spockframework.org/spock/docs/2.3/utilities.html#_strict_match

There is a NOTE section saying Both operands must be Iterable for this to work. I think the note should be extended to state that the operator can be used only in conditions.

[Vampire]

The heading says it. The heading is "Collection Conditions". And the part I linked to explains where you have a condition when.

If you for example have in the snippet [] ==~ [1] instead of [] ==~ [], it will compile and run fine and not fail, as it is not a condition either, but just an expression statement evaluating to false.

Never trust a test you did not see failing for the correct reason. :-)

But anyway, I'll leave the decision with @leonard84 .