Update String#camelize to provide feedback when a wrong option is sent

[ricardotk002]

Summary

String#camelize was returning nil without any feedback when an
invalid option was sent as parameter. This update makes the method to
raise an ArgumentError when the option passed is invalid, similar to what
Ruby does for String#downcase (and other methods) in 2.4.1.

Previously:

'one_two'.camelize(true)
=> nil

Now:

'one_two'.camelize(true)
=> ArgumentError: Invalid option, use either :upper or :lower.

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[lugray]

I think principle of least surprise would have 'one_two'.camelize(true) behave like ActiveSupport::Inflector.camelize('one_two', true). What about

uppercase_first_letter = {upper: true, lower: false}.fetch(first_letter, first_letter)
ActiveSupport::Inflector.camelize(self, uppercase_first_letter)

[ricardotk002]

hey @lugray 👋 , that was my first approach but then I realized that it would make it accept any truthy/falsy value and still work somehow. Another option I considered was to return the same string without modifications, but this is pretty much the same of how it is now: users don't get much feedback about what's happening and they might need to go to the docs in order to learn more about it.

I went to Ruby's String docs to learn more of other methods and I think this implementation follows those designs. You can check String#downcase https://ruby-doc.org/core-2.4.1/String.html#method-i-downcase

'one_two'.downcase(true)
=> ArgumentError: invalid option