Java8 - Max number of arguments in a step definition

[petosorus]

Summary

Using Kotlin, I noticed a step definition cannot have more than 9 arguments. I have some fairly complicated steps that need 10 or more arguments and that I cannot strip anymore.

I looked into it and it is a Cucumber limitation, coming from the fact that it defines interfaces for 1 to 9 arguments but no more (in StepdefBody.java)

Expected Behavior

It would nice to have the possibility of using more than 9 arguments.

Current Behavior

No more than 9 arguments can be put in for a step.

Possible Solution

Would it be possible to rely not on hardcoded interfaces for 1 to 9 arguments but to something with a dynamic number of arguments?
I'm willing to propose a fix that way, just need to look into code more.

Otherwise, I could add more interfaces, but that's ugly and not really desirable.

Context & Motivation

I have a complicated step that needs either more than 9 arguments, an ugly hack of splitting one of the arguments to get more data out of this limitation, or a rethinking of the way we write feature tests which would not be as close as reality.

Your Environment

• Version used: 4.2.2

[mlvandijk]

@petosorus To better understand your use case, could you provide a real world example of when you would want to use more than 10 / unlimited arguments?

[petosorus]

Yeah, here you go

Then("^A job exists on scheduling simulation (\\d+) on resource (\\w+)/(\\w+)/(\\w+) for item (\\w+) of (\\d+)/(\\w+) from J(\\d+) - (\\w+) to J(\\d+) - (\\w+)$") {
	simulationId: Int, companyCode: String, establishmentCode: String, resourceCode: String,
	itemCode: String, quantity: Int, unitCode: String,
	startDay: Int,startTime: String, endDay: Int, endTime: String -> {
     // Stuff
} 

Basically we created jobs that are time dependant, and we want to check they exist at the right time on the right day of the week (the "J(\d+)" part).

Only unique thing on those would be an id as it's dynamic data do everything we have as an argument here is useful.

[mlvandijk]

Some thoughts (that may or may not help you - feel free to ignore if you disagree): 1. This example contains a lot of detail. Personally, I would find this hard to read and immediately understand what your system does. If this scenario is about a job existing at a particular day, is the resource information really important? And if not, could you push that down to the step definition? 2. If the resource IS important to the scenario, and you need to check for different resources, could you create a set of "resource" objects with companyCode, establishmentCode, resourceCode based on a meaningful name for that resource? 3. If you really need all of the above, you could still put day & time into one string and parse that into a DateTime? which would save 2 parameters...

[petosorus]

I agree we could be more concise, but my interrogation still stands.
Is there any reason why there is a hard limit on 9 arguments? If not, why was it done the way it is instead of having something like varargs?

[mlvandijk]

Honestly, I wouldn't know. The only reason I could think of would be that adding unlimited arguments would be a bit of a smell.

[mpkorstanje]

There currently is no Kotlin backend so we are using the Java backend instead. In Java a lambda needs a backing functional interface. And for Java to be able to determine the type of each argument it also has to be a generic interface. So we generate the lambdas and interfaces using a nice bit of Groovy templating. The reason the limit is 9 has a rather practical cause. It's the largest single digit number. So without padding any zeros the class names still look good.

While its possible to increase the number of allowed parameter it would probably be better to implement a Kotlin backend that uses kotlin.Function. Unlike Java it should be possible to directly get the parameters from the lambda by using Function.reflect, thus no need to limit the number of parameters at all.

But I haven't tried this yet. Feel free to give it a shot!

[mpkorstanje]

Continued in #1829