1 files changed, 149 insertions, 0 deletions
diff --git a/lib/irb/ext/eval_history.rb b/lib/irb/ext/eval_history.rb
new file mode 100644
index 0000000000..6c21ff00ee
--- /dev/null
+++ b/lib/irb/ext/eval_history.rb
@@ -0,0 +1,149 @@
+# frozen_string_literal: true
+#
+#   history.rb -
+#   	by Keiju ISHITSUKA(keiju@ruby-lang.org)
+#
+
+module IRB # :nodoc:
+
+  class Context
+
+    NOPRINTING_IVARS.push "@eval_history_values"
+
+    # See #set_last_value
+    alias _set_last_value set_last_value
+
+    def set_last_value(value)
+      _set_last_value(value)
+
+      if defined?(@eval_history) && @eval_history
+        @eval_history_values.push @line_no, @last_value
+        workspace.evaluate "__ = IRB.CurrentContext.instance_eval{@eval_history_values}"
+      end
+
+      @last_value
+    end
+
+    remove_method :eval_history= if method_defined?(:eval_history=)
+    # The command result history limit. This method is not available until
+    # #eval_history= was called with non-nil value (directly or via
+    # setting <code>IRB.conf[:EVAL_HISTORY]</code> in <code>.irbrc</code>).
+    attr_reader :eval_history
+    # Sets command result history limit. Default value is set from
+    # <code>IRB.conf[:EVAL_HISTORY]</code>.
+    #
+    # +no+ is an Integer or +nil+.
+    #
+    # Returns +no+ of history items if greater than 0.
+    #
+    # If +no+ is 0, the number of history items is unlimited.
+    #
+    # If +no+ is +nil+, execution result history isn't used (default).
+    #
+    # EvalHistory values are available via <code>__</code> variable, see
+    # IRB::EvalHistory.
+    def eval_history=(no)
+      if no
+        if defined?(@eval_history) && @eval_history
+          @eval_history_values.size(no)
+        else
+          @eval_history_values = EvalHistory.new(no)
+          IRB.conf[:__TMP__EHV__] = @eval_history_values
+          workspace.evaluate("__ = IRB.conf[:__TMP__EHV__]")
+          IRB.conf.delete(:__TMP_EHV__)
+        end
+      else
+        @eval_history_values = nil
+      end
+      @eval_history = no
+    end
+  end
+
+  # Represents history of results of previously evaluated commands.
+  #
+  # Available via <code>__</code> variable, only if <code>IRB.conf[:EVAL_HISTORY]</code>
+  # or <code>IRB::CurrentContext().eval_history</code> is non-nil integer value
+  # (by default it is +nil+).
+  #
+  # Example (in `irb`):
+  #
+  #    # Initialize history
+  #    IRB::CurrentContext().eval_history = 10
+  #    # => 10
+  #
+  #    # Perform some commands...
+  #    1 + 2
+  #    # => 3
+  #    puts 'x'
+  #    # x
+  #    # => nil
+  #    raise RuntimeError
+  #    # ...error raised
+  #
+  #    # Inspect history (format is "<item number> <evaluated value>":
+  #    __
+  #    # => 1 10
+  #    # 2 3
+  #    # 3 nil
+  #
+  #    __[1]
+  #    # => 10
+  #
+  class EvalHistory
+
+    def initialize(size = 16)  # :nodoc:
+      @size = size
+      @contents = []
+    end
+
+    def size(size) # :nodoc:
+      if size != 0 && size < @size
+        @contents = @contents[@size - size .. @size]
+      end
+      @size = size
+    end
+
+    # Get one item of the content (both positive and negative indexes work).
+    def [](idx)
+      begin
+        if idx >= 0
+          @contents.find{|no, val| no == idx}[1]
+        else
+          @contents[idx][1]
+        end
+      rescue NameError
+        nil
+      end
+    end
+
+    def push(no, val)  # :nodoc:
+      @contents.push [no, val]
+      @contents.shift if @size != 0 && @contents.size > @size
+    end
+
+    alias real_inspect inspect
+
+    def inspect  # :nodoc:
+      if @contents.empty?
+        return real_inspect
+      end
+
+      unless (last = @contents.pop)[1].equal?(self)
+        @contents.push last
+        last = nil
+      end
+      str = @contents.collect{|no, val|
+        if val.equal?(self)
+          "#{no} ...self-history..."
+        else
+          "#{no} #{val.inspect}"
+        end
+      }.join("\n")
+      if str == ""
+        str = "Empty."
+      end
+      @contents.push last if last
+      str
+    end
+  end
+end