Asserting methods to return Assert<T> instead of Unit

[valeriyo]

I'm migrating from AssertJ, with following asserting method chaining:

   assertThat(array).hasSize(2).isEqualTo(...)

However, in AssertK - this is not possible, because hasSize (and other methods) return Unit instead of this.

What's the reasoning for this?

P.S. I know that there is an alternative assertThat(array).all { ... } but this makes migrating from AssertJ a bit of a pain.

[evant]

While method chaining can be useful it can also be confusing when it's used it different ways in different places. We chose to use chaining only to narrow what's being asserted on. This way each method in the chain is relevant to the one before it. For example:

assertThat(person).isNotNull().prop(Person::name).isEqualTo(...)

We go Person? -> Person -> String.

As you mentioned, when you want to have multiple assertions on the same value, you can use all and it's clear what you are doing and still quite concise

assertThat(array).all {
  hasSize(2)
  isEqualTo(...)
}

One note: all and it's counterpart assertAll do work differently than a chain in assertj in that they use soft assertions. So if hasSize and isEqualTo both failed you'd get 2 error messages. You could alternatively choose to have the same fail-fast behavior instead by using apply.

assertThat(array).apply {
  hasSize(2)
  isEqualTo(...)
}

this makes migrating from AssertJ a bit of a pain

That's fair. Though while this library was inspired by assertj, having 1-1 feature parity to make migration easy was never a goal.

[valeriyo]

Makes sense, thank you