Support optional parameters in step bindings

[304NotModified]

Would be cool if we support optional parameters, e.g.

[Given(@"Add two numbers (.*) (.*) (.*)")]
[Given(@"Add two numbers (.*) (.*)")] 
public void Testtheconditionwith(string a, string b, string c = "a")
{

}

From https://stackoverflow.com/questions/65853669/how-to-accommodate-specflow-step-definition-to-accept-deferent-number-of-paramet

See also #509

[304NotModified]

I did a small POC, I think this has to be done for this:

• Update the engine, see my POC: POC optional parameters in step bindings #511
• Update the VS2022 plugin: https://github.com/reqnroll/Reqnroll.VisualStudio/blob/3555492e4410f15daa2973436b5520000dc4fb75/Reqnroll.VisualStudio/Discovery/ProjectStepDefinitionBinding.cs#L60
• Update the Rider plugin
• Update the docs https://docs.reqnroll.net/latest/automation/step-definitions.html, see also Improve docs about step parameters #508

[clrudolphi]

Will need to consider impacts to steps that accept DataTables or DataStrings as input (as the last parameter), and those that depend upon use of a StepArgumentTransformer.

[gasparnagy]

While form most of us the regex step definitions are the familiar ones, but the future is cucumber expressions. In a few years no one will use regex anymore (at least this happened with Cucumber). So for this feature we should check if there is a way to express optional parameters in cucumber expressions and also include that into the concept.

[Code-Grump]

I think the example here could be written with a pair of cucumber expressions.

What's interesting seems to be the notion of supporting C#'s optional parameters feature, rather than requiring a separate overload with the appropriate number of arguments.

[mooragor]

I was having a look at the Cucumber expressions (to replace regexes I'm used to using) and found them to lack a lot of the really useful stuff you can do with a regex for guiding writers of the feature file.

For example, I couldn't work out (with cucumber expressions) how you could define the following step:

"I select (best|worst|intermediate) option"

The closest I could see would be

"I select the {word} option"

When the step definition can only cope with one of those 3 options, being able to specify what is allowable in the expression itself lets IDE autocomplete guide the writer of the feature file.

Regex also enables optional parameters with things like "I do this(?:| and also that)", letting a single step definition implement the required similar logic without needing to duplicate code or have empty boilerplate steps that just pass a predefined variable to a more complete method.

I'm curious to know why you would expect the future to be Cucumber expressions, and not regex? - regex is definitely more complex to understand, but seems to be far more powerful. I'm not terribly active in the community, so don't really know anything about the trends in usage!

[clrudolphi]

For example, I couldn't work out (with cucumber expressions) how you could define the following step:

"I select (best|worst|intermediate) option"

Cucumber Expression support for optionals/alternatives works a bit differently. I'll point you to this page on the Cucumber site.
TLDR: you'll need to define an enum and create a StepArgumentTransformation.

[mooragor]

I had seen that, but it seemed overly complex compared to the regex.
I suppose it's one of the joys of programming, there are usually at least 5 different ways to achieve the same outcome!

[mooragor]

I'd really appreciate proper support for optional parameters. Regexes have worked for that in the past and removing that capability as part of the swap to Reqnroll is going to cost me a chunk of effort.
I saw the extension someone suggested to make it work (#509), but it would be so much better if this was 'built in' to Reqnroll. I dislike having to make custom modifications to software as it makes it much harder to keep the same capabilities across multiple projects.