Limit number of method/closure parameters rule

[delebedev]

Time to time I raise this issue with colleagues: there is no proven number to stick, but IMHO anything with 5 or more parameters should be considered as suspicious (might be a good place to use "Introduce Parameter object" refactoring).

I see it as an AST rule that raises warning for methods/functions/closures with 5 or more arguments (configurable).

Edit: probably it should ignore init methods though (value objects usually have tons of parameters)

[scottrhoyt]

Interesting idea. Do you think this should or shouldn't count parameters with default values?

[delebedev]

@scottrhoyt that's a good question indeed 👍
Just thinking out loud: declaration of method with 4+ parameters is not often a problem, developer has hard times when he reads place where such method is called or invokes such method. Assuming that I would say that we can:

• make requirement less strict for method containing optional arguments (math to be discussed)
• completely ignore parameters with default values because they can be totally ignored when calling method

[scottrhoyt]

Without thinking about it too much, I think I would vote for option number 2 since it is simpler and clearer. Ultimately I think it is more important for this rule to protect potential callers as opposed to the function writer.