Pattern matching Success containing an array returns a surprising result

[ygt-mikekchar]

Describe the bug

When you pattern match a Result that happens to contain an array in a case statement, the destructured contents of the Result contains the contents of the array, not the array.

We discovered this because we have a function that decodes JSON and returns the contents in a Result (Success if it parsed correctly, Failure if it didn't). We don't know ahead of time whether or not the Result will contain an array or not. It's not really a problem to use an if statement in this situation (result.value! contains the correct value), but it's very surprising that you have to.

To Reproduce

result = Success([42])

case result
in Success(value)
  value
in Failure(err)
  err
end

Returns 42

If instead you set: result = Success([1, 2, 3, 4])

The above case statement will generate a NoMatchingPatternError.

Expected behavior

The case statement should return [42] (or in the second instance [1, 2, 3, 4])

My environment

• Affects my production application: YES/NO
• Ruby version: 3.0.1
• OS: N/A

[flash-gordon]

Yeah, that was covered in docs https://dry-rb.org/gems/dry-monads/1.3/pattern-matching/#matching-array-values