[Ruby 3.0 support] Add category kwarg to Kernel.warn and Warning.warn

[Strech]

Also, some existing behaviour were ported to other Warning methods, like type check in Warning#[] and Warnign#[]=

In addition, some ruby specs were added ruby/spec#897

Implementation concerns

1. I'm a bit concerned about that line. In MRI implementation C-code shares that functionality between warn and [], both call the same function which returns internal category value, but not sure that I can reuse it as I did
2. Not sure that I fully understand that line does it mean that I have to copy some checks like inclusion in a pre-defined list of values?

[eregon]

• I'm a bit concerned about that line. In MRI implementation C-code shares that functionality between warn and [], both call the same function which returns internal category value, but not sure that I can reuse it as I did

Calling [] in itself is fine, but it's not ideal to read the value needlessly.
I think it's better to have a method checking if the category is correct.

Could you add a method doing that, under module Truffle::WarningOperations which can define in the same file?

• Not sure that I fully understand that line does it mean that I have to copy some checks like inclusion in a pre-defined list of values?

I can't find what this link points to, can you post the comment in the diff instead?

[Strech]

Calling [] in itself is fine, but it's not ideal to read the value needlessly.
I think it's better to have a method checking if the category is correct.

Ok, have exactly the same thoughts about unnecessary reads, will adjust the code

I can't find what this link points to, can you post the comment in the diff instead?

It's because it's hidden, oh, here is a file link

truffleruby/src/main/ruby/truffleruby/core/kernel.rb

Lines 649 to 653 in 9bcfd4f

	if Primitive.object_equal(self, Warning) # avoid recursion when redefining Warning#warn
	unless message.encoding.ascii_compatible?
	raise Encoding::CompatibilityError, "ASCII incompatible encoding: #{message.encoding}"
	end
	$stderr.write message

[eregon]

That's a weird corner case when people incorrectly redefine Warning#warn to super into Kernel#warn.
I think it doesn't matter too much, but yeah let's do the category check there too for consistency.

[Strech]

@eregon I've done with all the suggestions (except writing test, since there is one already)

[eregon]

Thanks, this looks great! (and sorry for the late review)

[Strech]

@eregon Oh, finally get what you've meant by old warn support, thanks for adjustments!