pry--pry/lib/pry/commands/cd.rb

class Pry
  Pry::Commands.create_command "cd" do
    group "Context"
    description "Move into a new context (object or scope)."

    banner <<-BANNER
      Usage: cd [OPTIONS] [--help]

      Move into new context (object or scope). As in unix shells use
      `cd ..` to go back, `cd /` to return to Pry top-level and `cd -`
      to toggle between last two scopes).
      Complex syntax (e.g `cd ../@x/y`) also supported.

      e.g: `cd @x`
      e.g: `cd ..`
      e.g: `cd /`
      e.g: `cd -`

      https://github.com/pry/pry/wiki/State-navigation#wiki-Changing_scope
    BANNER

    def process
      # Extract command arguments. Delete blank arguments like " ", but
      # don't delete empty strings like "".
      path      = arg_string.split(/\//).delete_if { |a| a =~ /\A\s+\z/ }
      stack     = _pry_.binding_stack.dup
      old_stack = state.old_stack || []

      # Special case when we only get a single "/", return to root.
      if path.empty?
        state.old_stack = stack.dup unless old_stack.empty?
        stack = [stack.first]
      end

      path.each_with_index do |context, i|
        begin
          case context.chomp
          when ""
            state.old_stack = stack.dup
            stack = [stack.first]
          when "::"
            state.old_stack = stack.dup
            stack.push(TOPLEVEL_BINDING)
          when "."
            next
          when ".."
            unless stack.size == 1
              # Don't rewrite old_stack if we're in complex expression
              # (e.g.: `cd 1/2/3/../4).
              state.old_stack = stack.dup if path.first == ".."
              stack.pop
            end
          when "-"
            unless old_stack.empty?
              # Interchange current stack and old stack with each other.
              stack, state.old_stack = state.old_stack, stack
            end
          else
            state.old_stack = stack.dup if i == 0
            stack.push(Pry.binding_for(stack.last.eval(context)))
          end

        rescue RescuableException => e
          # Restore old stack to its initial values.
          state.old_stack = old_stack

          output.puts "Bad object path: #{arg_string.chomp}. Failed trying to resolve: #{context}"
          output.puts e.inspect
          return
        end
      end

      _pry_.binding_stack = stack
    end
  end
end