implement cat --in (fixes #330)

lib/pry/default_commands/shell.rb

@@ -31,7 +31,7 @@ class Pry
 
       alias_command "file-mode", "shell-mode"
 
-      command "cat", "Show output of file FILE. Type `cat --help` for more information." do |*args|
+      command "cat", "Show code from a file or Pry's input buffer. Type `cat --help` for more information." do |*args|
         start_line = 0
         end_line = -1
         file_name = nil
@@ -68,6 +68,8 @@ class Pry
             end
           end
 
+          opt.on :i, :in, "Show entries from Pry's input expression history. Takes an index or range.", :optional => true, :as => Range, :default => -5..-1
+
           opt.on :l, "line-numbers", "Show line numbers."
           opt.on :t, :type, "The specific file type for syntax higlighting (e.g ruby, python)", true, :as => Symbol
           opt.on :f, :flood, "Do not use a pager to view text longer than one screen."
@@ -86,19 +88,49 @@ class Pry
           file_name = args.shift
         end
 
-        if !file_name
-          raise CommandError, "Must provide a file name."
-        end
+        if opts.in?
+          normalized_range = absolute_index_range(opts[:i], _pry_.input_array.length)
+          input_items = _pry_.input_array[normalized_range] || []
+
+          zipped_items = normalized_range.zip(input_items).reject { |_, s| s.nil? || s == "" }
+
+          unless zipped_items.length > 0
+            raise CommandError, "No expressions found."
+          end
+
+          if opts[:i].is_a?(Range)
+            contents = ""
+
+            zipped_items.each do |i, s|
+              contents << "#{text.bold(i.to_s)}:\n"
+
+              code = syntax_highlight_by_file_type_or_specified(s, nil, :ruby)
+
+              if opts.l?
+                contents << text.indent(text.with_line_numbers(code, 1), 2)
+              else
+                contents << text.indent(code, 2)
+              end
+            end
+          else
+            contents = syntax_highlight_by_file_type_or_specified(zipped_items.first.last, nil, :ruby)
+          end
+        else
+          unless file_name
+            raise CommandError, "Must provide a file name."
+          end
+
+          begin
+            contents, _, _ = read_between_the_lines(file_name, start_line, end_line)
+          rescue Errno::ENOENT
+            raise CommandError, "Could not find file: #{file_name}"
+          end
 
-        begin
-          contents, _, _ = read_between_the_lines(file_name, start_line, end_line)
           contents = syntax_highlight_by_file_type_or_specified(contents, file_name, opts[:type])
-        rescue Errno::ENOENT
-          raise CommandError, "Could not find file: #{file_name}"
-        end
 
-        if opts.l?
-          contents = text.with_line_numbers contents, start_line + 1
+          if opts.l?
+            contents = text.with_line_numbers contents, start_line + 1
+          end
         end
 
         # add the arrow pointing to line that caused the exception

lib/pry/helpers/command_helpers.rb

@@ -86,13 +86,16 @@ class Pry
       end
 
       def syntax_highlight_by_file_type_or_specified(contents, file_name, file_type)
-        _, language_detected = file_map.find do |k, v|
-          Array(k).any? do |matcher|
-            matcher == File.extname(file_name) || matcher == File.basename(file_name)
+        if file_type
+          language_detected = file_type
+        else
+          _, language_detected = file_map.find do |k, v|
+            Array(k).any? do |matcher|
+              matcher == File.extname(file_name) || matcher == File.basename(file_name)
+            end
           end
         end
 
-        language_detected = file_type if file_type
         if Pry.color
           CodeRay.scan(contents, language_detected).term
         else
@@ -247,6 +250,25 @@ class Pry
         text.gsub(/^#{margin}/, '')
       end
 
+      def absolute_index_number(line_number, array_length)
+        if line_number >= 0
+          line_number
+        else
+          [array_length + line_number, 0].max
+        end
+      end
+
+      def absolute_index_range(range_or_number, array_length)
+        case range_or_number
+        when Range
+          a = absolute_index_number(range_or_number.begin, array_length)
+          b = absolute_index_number(range_or_number.end, array_length)
+        else
+          a = b = absolute_index_number(range_or_number, array_length)
+        end
+
+        Range.new(a, b)
+      end
     end
 
   end

lib/pry/helpers/text.rb

@@ -81,6 +81,14 @@ class Pry
             "#{self.send(color, adjusted_index)}: #{line}"
           end.join
         end
+
+        # Returns _text_ indented by _chars_ spaces.
+        #
+        # @param [String] text
+        # @param [Fixnum] chars
+        def indent(text, chars)
+          text.lines.map { |l| "#{' ' * chars}#{l}" }.join
+        end
       end
 
     end

lib/pry/history_array.rb

@@ -72,6 +72,8 @@ class Pry
     def size
       @count
     end
+    alias count size
+    alias length size
 
     def empty?
       size == 0

test/test_default_commands/test_shell.rb

@@ -9,6 +9,41 @@ describe "Pry::DefaultCommands::Shell" do
       end
     end
 
+    describe "with --in" do
+      it 'should display the last few expressions with indices' do
+        output = mock_pry("10", "20", "cat --in")
+        output.should =~ /^1:/
+        output.should =~ /^  10/
+        output.should =~ /^2:/
+        output.should =~ /^  20/
+      end
+    end
+
+    describe "with --in 1" do
+      it 'should display the first expression with no index' do
+        output = mock_pry("10", "20", "cat --in 1")
+        output.should.not =~ /^\d+:/
+        output.should =~ /^10/
+      end
+    end
+
+    describe "with --in -1" do
+      it 'should display the last expression with no index' do
+        output = mock_pry("10", "20", "cat --in -1")
+        output.should.not =~ /^\d+:/
+        output.should =~ /^20/
+      end
+    end
+
+    describe "with --in 1..2" do
+      it 'should display the given range with indices, omitting nils' do
+        output = mock_pry("10", "20", "cat --ex", ":hello", "cat --in 1..4")
+        output.should =~ /^1:/
+        output.should.not =~ /^3:/
+        output.should =~ /^  :hello/
+      end
+    end
+
     # this doesnt work so well on rbx due to differences in backtrace
     # so we currently skip rbx until we figure out a workaround
     describe "with --ex" do