Pin the version of parser/current to whatever Ruby version we're using

[jeffwidman]

Currently, we pull in whatever the latest version of parser/current is... if that is ahead of our actual Ruby version, then we can get warnings, which we currently silence:

dependabot-core/common/spec/warning_monkey_patch.rb

Lines 4 to 9 in 18bb480

	# Ignore parser warnings for ruby 2.7 minor version mismatches.
	# This is a recurring issue that occurs whenever the parser gets
	# ahead of our installed ruby version.
	%r{parser/current is loading parser/ruby27},
	/2.7.\d-compliant syntax, but you are running 2.7.\d/,
	%r{whitequark/parser}

However, there's another way to handle this--by having the parser version match whatever version of Ruby we're using.

See how the Rubocop project did it:

• Original issue: Parser issue rubocop/rubocop#9700
• Hacky solution of silencing the warning using $VERSOSE = nil: marcandre/rubocop-ast@7081f7c
• Cleaner solution of loading the parser version that corresponds to the ruby version: Avoid parser warning rubocop/rubocop#9702

[jeffwidman]

Actually, looking at https://github.com/whitequark/parser/blob/492871419b298e233bb788ec1793b7af7004e23e/lib/parser/current.rb#L95-L99 the warning can still be thrown even if we pin the parser to the current ruby minor version... if the patch versions are outdated. Since the parser doesn't appear to have patch versions--those regexes will catch all patch versions under the same comparison with the latest ruby patch version.

So closing as I don't think there's anything we can do here.