New rule: Param Pattern-Matching

[elbrujohalcon]

Consistent Param Pattern-Matching

Brief Description

When capturing a parameter using pattern matching you can either put the parameter name on the left (Param = #{pattern := ToMatch}) or right (#{pattern := ToMatch} = Param) side of the pattern that you use in the function clause. This rule will make sure you are consistent through your code and use always the same style.

Should be on by default?

YES

Options

• preferred_style :: left | right (default: left)

Reasoning

Paraphrasing Credo documentation:

When capturing a parameter using pattern matching you can either put the parameter name before or after the value i.e.

parse(#{ok := Values} = Pair) ->
…

…or…

parse(Pair = #{ok := Values}) ->
…

Neither of these is better than the other, but it seems a good idea not to mix the two patterns in the same codebase.
While this is not necessarily a concern for the correctness of your code, you should use a consistent style throughout your codebase.

Origin (#281)

Inspired by the Consistency.ParameterPatternMatching rule from Credo