1 files changed, 155 insertions, 0 deletions
diff --git a/lib/irb/command/ls.rb b/lib/irb/command/ls.rb
new file mode 100644
index 0000000000..cbd9998bc4
--- /dev/null
+++ b/lib/irb/command/ls.rb
@@ -0,0 +1,155 @@
+# frozen_string_literal: true
+
+require "reline"
+require "stringio"
+
+require_relative "../pager"
+require_relative "../color"
+
+module IRB
+  # :stopdoc:
+
+  module Command
+    class Ls < Base
+      include RubyArgsExtractor
+
+      category "Context"
+      description "Show methods, constants, and variables."
+
+      help_message <<~HELP_MESSAGE
+        Usage: ls [obj] [-g [query]]
+
+          -g [query]  Filter the output with a query.
+      HELP_MESSAGE
+
+      def execute(arg)
+        if match = arg.match(/\A(?<target>.+\s|)(-g|-G)\s+(?<grep>.+)$/)
+          if match[:target].empty?
+            use_main = true
+          else
+            obj = @irb_context.workspace.binding.eval(match[:target])
+          end
+          grep = Regexp.new(match[:grep])
+        else
+          args, kwargs = ruby_args(arg)
+          use_main = args.empty?
+          obj = args.first
+          grep = kwargs[:grep]
+        end
+
+        if use_main
+          obj = irb_context.workspace.main
+          locals = irb_context.workspace.binding.local_variables
+        end
+
+        o = Output.new(grep: grep)
+
+        klass  = (obj.class == Class || obj.class == Module ? obj : obj.class)
+
+        o.dump("constants", obj.constants) if obj.respond_to?(:constants)
+        dump_methods(o, klass, obj)
+        o.dump("instance variables", obj.instance_variables)
+        o.dump("class variables", klass.class_variables)
+        o.dump("locals", locals) if locals
+        o.print_result
+      end
+
+      def dump_methods(o, klass, obj)
+        singleton_class = begin obj.singleton_class; rescue TypeError; nil end
+        dumped_mods = Array.new
+        ancestors = klass.ancestors
+        ancestors = ancestors.reject { |c| c >= Object } if klass < Object
+        singleton_ancestors = (singleton_class&.ancestors || []).reject { |c| c >= Class }
+
+        # singleton_class' ancestors should be at the front
+        maps = class_method_map(singleton_ancestors, dumped_mods) + class_method_map(ancestors, dumped_mods)
+        maps.each do |mod, methods|
+          name = mod == singleton_class ? "#{klass}.methods" : "#{mod}#methods"
+          o.dump(name, methods)
+        end
+      end
+
+      def class_method_map(classes, dumped_mods)
+        dumped_methods = Array.new
+        classes.map do |mod|
+          next if dumped_mods.include? mod
+
+          dumped_mods << mod
+
+          methods = mod.public_instance_methods(false).select do |method|
+            if dumped_methods.include? method
+              false
+            else
+              dumped_methods << method
+              true
+            end
+          end
+
+          [mod, methods]
+        end.compact
+      end
+
+      class Output
+        MARGIN = "  "
+
+        def initialize(grep: nil)
+          @grep = grep
+          @line_width = screen_width - MARGIN.length # right padding
+          @io = StringIO.new
+        end
+
+        def print_result
+          Pager.page_content(@io.string)
+        end
+
+        def dump(name, strs)
+          strs = strs.grep(@grep) if @grep
+          strs = strs.sort
+          return if strs.empty?
+
+          # Attempt a single line
+          @io.print "#{Color.colorize(name, [:BOLD, :BLUE])}: "
+          if fits_on_line?(strs, cols: strs.size, offset: "#{name}: ".length)
+            @io.puts strs.join(MARGIN)
+            return
+          end
+          @io.puts
+
+          # Dump with the largest # of columns that fits on a line
+          cols = strs.size
+          until fits_on_line?(strs, cols: cols, offset: MARGIN.length) || cols == 1
+            cols -= 1
+          end
+          widths = col_widths(strs, cols: cols)
+          strs.each_slice(cols) do |ss|
+            @io.puts ss.map.with_index { |s, i| "#{MARGIN}%-#{widths[i]}s" % s }.join
+          end
+        end
+
+        private
+
+        def fits_on_line?(strs, cols:, offset: 0)
+          width = col_widths(strs, cols: cols).sum + MARGIN.length * (cols - 1)
+          width <= @line_width - offset
+        end
+
+        def col_widths(strs, cols:)
+          cols.times.map do |col|
+            (col...strs.size).step(cols).map do |i|
+              strs[i].length
+            end.max
+          end
+        end
+
+        def screen_width
+          Reline.get_screen_size.last
+        rescue Errno::EINVAL # in `winsize': Invalid argument - <STDIN>
+          80
+        end
+      end
+      private_constant :Output
+    end
+  end
+
+  # :startdoc:
+end