Output GitHub Actions annotations for brew style.

Library/Homebrew/utils/github/actions.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module GitHub
+  # Helper functions for interacting with GitHub Actions.
+  #
+  # @api private
+  module Actions
+    def self.escape(string)
+      string.gsub(/\r/, "%0D")
+            .gsub(/\n/, "%0A")
+            .gsub(/]/, "%5D")
+            .gsub(/;/, "%3B")
+    end
+
+    # Helper class for formatting annotations on GitHub Actions.
+    class Annotation
+      def initialize(type, message, file: nil, line: nil, column: nil)
+        raise ArgumentError, "Unsupported type: #{type.inspect}" unless [:warning, :error].include?(type)
+
+        @type = type
+        @message = String(message)
+        @file = Pathname(file) if file
+        @line = Integer(line) if line
+        @column = Integer(column) if column
+      end
+
+      def to_s
+        file = "file=#{Actions.escape(@file.to_s)}" if @file
+        line = "line=#{@line}" if @line
+        column = "col=#{@column}" if @column
+
+        metadata = [*file, *line, *column].join(",").presence&.prepend(" ")
+
+        "::#{@type}#{metadata}::#{Actions.escape(@message)}"
+      end
+    end
+  end
+end