Sometimes I wish there was some way to use matcher...

# kotest

[Emil Kantis]

Sometimes I wish there was some way to use matchers as predicates out-of-the-box. For instance, today I found myself doing

myListOfJsonStuff.filter {
  runCatching {
    it shouldEqualSpecifiedJson """ { "type": "FOO" } """
  }.isSuccess
}

Anyone else done something similar? Or maybe figured some way to do this neatly with existing functionality?

[sam]

Maybe we add a filter version of inspectors?

[Emil Kantis]

Yeah was thinking of suggesting something like filterMatching(t: (T) -> Unit) , or perhaps filterMatching(matcher: Matcher<T>)

[sam]

The former allows you to run multiple and matches how inspectors look

[Emil Kantis]

Will add some test too before marking as ready.. trivial to implement given the inspector utilities 🙂 https://github.com/kotest/kotest/pull/4658

[Klitos Kyriacou]

This MR uses the anti-pattern of exceptions as flow control. It's not usually a problem for a unit test, but it can slow down some unit tests due to the time it takes to construct an exception with all the stack trace information that's then thrown away. Therefore, would it be a good idea to also have filterMatching(matcher: Matcher<T>) which doesn't involve exceptions? On the other hand, users can already easily use the stdlib's filter for that.