Polyfill Kernel#warn category parameter

Author: kddnewton

lib/prism.rb

@@ -68,6 +68,7 @@ def self.load(source, serialized, freeze = false)
 end
 
 require_relative "prism/polyfill/byteindex"
+require_relative "prism/polyfill/warn"
 require_relative "prism/node"
 require_relative "prism/node_ext"
 require_relative "prism/parse_result"

lib/prism/node_ext.rb

@@ -9,7 +9,7 @@ def deprecated(*replacements) # :nodoc:
       location = location[0].label if location
       suggest = replacements.map { |replacement| "#{self.class}##{replacement}" }
 
-      warn(<<~MSG)
+      warn(<<~MSG, uplevel: 1, category: :deprecated)
         [deprecation]: #{self.class}##{location} is deprecated and will be \
         removed in the next major version. Use #{suggest.join("/")} instead.
         #{(caller(1, 3) || []).join("\n")}

lib/prism/polyfill/warn.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+# Polyfill for Kernel#warn with the category parameter. Not all Ruby engines
+# have Method#parameters implemented, so we check the arity instead if
+# necessary.
+if (method = Kernel.instance_method(:warn)).respond_to?(:parameters) ? method.parameters.none? { |_, name| name == :category } : (method.arity == -1)
+  Kernel.prepend(
+    Module.new {
+      def warn(*msgs, uplevel: nil, category: nil) # :nodoc:
+        uplevel =
+          case uplevel
+          when nil
+            1
+          when Integer
+            uplevel + 1
+          else
+            uplevel.to_int + 1
+          end
+
+        super(*msgs, uplevel: uplevel)
+      end
+    }
+  )
+
+  Object.prepend(
+    Module.new {
+      def warn(*msgs, uplevel: nil, category: nil) # :nodoc:
+        uplevel =
+          case uplevel
+          when nil
+            1
+          when Integer
+            uplevel + 1
+          else
+            uplevel.to_int + 1
+          end
+
+        super(*msgs, uplevel: uplevel)
+      end
+    }
+  )
+end

lib/prism/translation/parser.rb

@@ -60,7 +60,7 @@ def initialize(message, level, reason, location)
       #
       def initialize(builder = Prism::Translation::Parser::Builder.new, parser: Prism)
         if !builder.is_a?(Prism::Translation::Parser::Builder)
-          warn(<<~MSG, uplevel: 1)
+          warn(<<~MSG, uplevel: 1, category: :deprecated)
             [deprecation]: The builder passed to `Prism::Translation::Parser.new` is not a \
             `Prism::Translation::Parser::Builder` subclass. This will raise in the next major version.
           MSG

prism.gemspec

@@ -89,6 +89,7 @@ Gem::Specification.new do |spec|
     "lib/prism/polyfill/append_as_bytes.rb",
     "lib/prism/polyfill/byteindex.rb",
     "lib/prism/polyfill/unpack1.rb",
+    "lib/prism/polyfill/warn.rb",
     "lib/prism/reflection.rb",
     "lib/prism/relocation.rb",
     "lib/prism/serialize.rb",