1 files changed, 114 insertions, 0 deletions
diff --git a/railties/lib/rails/command.rb b/railties/lib/rails/command.rb
new file mode 100644
index 0000000000..f09aa3ae0d
--- /dev/null
+++ b/railties/lib/rails/command.rb
@@ -0,0 +1,114 @@
+# frozen_string_literal: true
+
+require "active_support"
+require "active_support/dependencies/autoload"
+require "active_support/core_ext/enumerable"
+require "active_support/core_ext/object/blank"
+
+require "thor"
+
+module Rails
+  module Command
+    extend ActiveSupport::Autoload
+
+    autoload :Spellchecker
+    autoload :Behavior
+    autoload :Base
+
+    include Behavior
+
+    HELP_MAPPINGS = %w(-h -? --help)
+
+    class << self
+      def hidden_commands # :nodoc:
+        @hidden_commands ||= []
+      end
+
+      def environment # :nodoc:
+        ENV["RAILS_ENV"].presence || ENV["RACK_ENV"].presence || "development"
+      end
+
+      # Receives a namespace, arguments and the behavior to invoke the command.
+      def invoke(full_namespace, args = [], **config)
+        namespace = full_namespace = full_namespace.to_s
+
+        if char = namespace =~ /:(\w+)$/
+          command_name, namespace = $1, namespace.slice(0, char)
+        else
+          command_name = namespace
+        end
+
+        command_name, namespace = "help", "help" if command_name.blank? || HELP_MAPPINGS.include?(command_name)
+        command_name, namespace = "version", "version" if %w( -v --version ).include?(command_name)
+
+        command = find_by_namespace(namespace, command_name)
+        if command && command.all_commands[command_name]
+          command.perform(command_name, args, config)
+        else
+          find_by_namespace("rake").perform(full_namespace, args, config)
+        end
+      end
+
+      # Rails finds namespaces similar to Thor, it only adds one rule:
+      #
+      # Command names must end with "_command.rb". This is required because Rails
+      # looks in load paths and loads the command just before it's going to be used.
+      #
+      #   find_by_namespace :webrat, :rails, :integration
+      #
+      # Will search for the following commands:
+      #
+      #   "rails:webrat", "webrat:integration", "webrat"
+      #
+      # Notice that "rails:commands:webrat" could be loaded as well, what
+      # Rails looks for is the first and last parts of the namespace.
+      def find_by_namespace(namespace, command_name = nil) # :nodoc:
+        lookups = [ namespace ]
+        lookups << "#{namespace}:#{command_name}" if command_name
+        lookups.concat lookups.map { |lookup| "rails:#{lookup}" }
+
+        lookup(lookups)
+
+        namespaces = subclasses.index_by(&:namespace)
+        namespaces[(lookups & namespaces.keys).first]
+      end
+
+      # Returns the root of the Rails engine or app running the command.
+      def root
+        if defined?(ENGINE_ROOT)
+          Pathname.new(ENGINE_ROOT)
+        elsif defined?(APP_PATH)
+          Pathname.new(File.expand_path("../..", APP_PATH))
+        end
+      end
+
+      def print_commands # :nodoc:
+        commands.each { |command| puts("  #{command}") }
+      end
+
+      private
+        COMMANDS_IN_USAGE = %w(generate console server test test:system dbconsole new)
+        private_constant :COMMANDS_IN_USAGE
+
+        def commands
+          lookup!
+
+          visible_commands = (subclasses - hidden_commands).flat_map(&:printing_commands)
+
+          (visible_commands - COMMANDS_IN_USAGE).sort
+        end
+
+        def command_type # :doc:
+          @command_type ||= "command"
+        end
+
+        def lookup_paths # :doc:
+          @lookup_paths ||= %w( rails/commands commands )
+        end
+
+        def file_lookup_paths # :doc:
+          @file_lookup_paths ||= [ "{#{lookup_paths.join(',')}}", "**", "*_command.rb" ]
+        end
+    end
+  end
+end