Merge pull request #22457 from ccallebs/rails-commands-infrastructure

Add Rails command infrastructure

1 files changed, 78 insertions, 0 deletions

diff --git a/railties/lib/rails/commands/command.rb b/railties/lib/rails/commands/command.rb
new file mode 100644
index 0000000000..ffd1a50c79
--- /dev/null
+++ b/railties/lib/rails/commands/command.rb
@@ -0,0 +1,78 @@
+module Rails
+  module Commands
+    class Command
+      attr_reader :argv
+
+      def initialize(argv = '')
+        @argv = argv
+
+        @option_parser = build_option_parser
+        @options = {}
+      end
+
+      def run(task_name)
+        command_name = self.class.command_name_for(task_name)
+
+        parse_options_for(command_name)
+        @option_parser.parse! @argv
+
+        if command_instance = command_for(command_name)
+          command_instance.public_send(command_name)
+        else
+          puts @option_parser
+        end
+      end
+
+      def self.options_for(command_name, &options_to_parse)
+        @@command_options[command_name] = options_to_parse
+      end
+
+      def self.command_name_for(task_name)
+        task_name.gsub(':', '_').to_sym
+      end
+
+      def self.set_banner(command_name, banner)
+        options_for(command_name) { |opts, _| opts.banner = banner }
+      end
+
+      def exists?(task_name)
+        command_name = self.class.command_name_for(task_name)
+        !command_for(command_name).nil?
+      end
+
+      private
+        @@commands = []
+        @@command_options = {}
+
+        def parse_options_for(command_name)
+          @@command_options.fetch(command_name, -> {}).call(@option_parser, @options)
+        end
+
+        def build_option_parser
+          OptionParser.new do |opts|
+            opts.on('-h', '--help', 'Show this help.') do
+              puts opts
+              exit
+            end
+          end
+        end
+
+        def self.inherited(command)
+          @@commands << command
+        end
+
+        def command_for(command_name)
+          klass = @@commands.find do |command|
+            command_instance_methods = command.public_instance_methods
+            command_instance_methods.include?(command_name)
+          end
+
+          if klass
+            klass.new(@argv)
+          else
+            nil
+          end
+        end
+    end
+  end
+end