[ruby/prism] Add Prism::Translation::ParserCurrent

It's not my favorite api but for users that currently use the same thing
from `parser`, moving over is more difficult
than it needs to be.

If you plan to support both old and new ruby versions, you definitly need to
branch somewhere on the ruby version
to either choose prism or parser.
But with prism you then need to enumerate all the versions again and choose the correct one.

Also, don't recommend to use `Prism::Translation::Parser` in docs. It's version-less
but actually always just uses Ruby 3.4 which is probably
not what the user intended.

Note: parser also warns when the patch version doesn't match what it expects. But I don't think prism has such a concept,
and anyways it would require releases anytime ruby releases, which I don't think is very desirable

https://github.com/ruby/prism/commit/77177f9e92

lib/prism/prism.gemspec

@@ -96,6 +96,7 @@ Gem::Specification.new do |spec|
     "lib/prism/string_query.rb",
     "lib/prism/translation.rb",
     "lib/prism/translation/parser.rb",
+    "lib/prism/translation/parser_current.rb",
     "lib/prism/translation/parser33.rb",
     "lib/prism/translation/parser34.rb",
     "lib/prism/translation/parser35.rb",

lib/prism/translation.rb

@@ -5,6 +5,7 @@ module Prism
   # syntax trees.
   module Translation # steep:ignore
     autoload :Parser, "prism/translation/parser"
+    autoload :ParserCurrent, "prism/translation/parser_current"
     autoload :Parser33, "prism/translation/parser33"
     autoload :Parser34, "prism/translation/parser34"
     autoload :Parser35, "prism/translation/parser35"

lib/prism/translation/parser_current.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+# typed: ignore
+
+module Prism
+  module Translation
+    case RUBY_VERSION
+    when /^3\.3\./
+      ParserCurrent = Parser33
+    when /^3\.4\./
+      ParserCurrent = Parser34
+    when /^3\.5\./
+      ParserCurrent = Parser35
+    else
+      # Keep this in sync with released Ruby.
+      parser = Parser34
+      warn "warning: `Prism::Translation::Current` is loading #{parser.name}, " \
+           "but you are running #{RUBY_VERSION.to_f}."
+      ParserCurrent = parser
+    end
+  end
+end

test/prism/ruby/parser_test.rb

@@ -155,6 +155,15 @@ module Prism
       assert_empty(warnings)
     end
 
+    if RUBY_VERSION >= "3.3"
+      def test_current_parser_for_current_ruby
+        major, minor, _patch = Gem::Version.new(RUBY_VERSION).segments
+        # Let's just hope there never is a Ruby 3.10 or similar
+        expected = major * 10 + minor
+        assert_equal(expected, Translation::ParserCurrent.new.version)
+      end
+    end
+
     def test_it_block_parameter_syntax
       it_fixture_path = Pathname(__dir__).join("../../../test/prism/fixtures/it.txt")