replaced explicit '(pry)' string with Pry.eval_path method

lib/pry/helpers/command_helpers.rb

@@ -43,7 +43,7 @@ class Pry
 
       def check_for_dynamically_defined_method(meth)
         file, _ = meth.source_location
-        if file =~ /(\(.*\))|<.*>/ && file != "(pry)"
+        if file =~ /(\(.*\))|<.*>/ && file != Pry.eval_path
           raise "Cannot retrieve source for dynamically defined method."
         end
       end
@@ -61,7 +61,7 @@ class Pry
           code = Pry::MethodInfo.info_for(meth).source
           code = strip_comments_from_c_code(code)
         when :ruby
-          if meth.source_location.first == "(pry)"
+          if meth.source_location.first == Pry.eval_path
 
             start_line = meth.source_location.last
             p = Pry.new(:input => StringIO.new(Pry.line_buffer[start_line..-1].join)).r(target)

lib/pry/pry_class.rb

@@ -122,6 +122,10 @@ class Pry
     # @return [Array] The Array of evaluated expressions.
     attr_accessor :line_buffer
 
+    # @return [String] The __FILE__ for the `eval()`. Should be "(pry)"
+    #   by default.
+    attr_accessor :eval_path
+
     # plugin forwardables
     def_delegators :@plugin_manager, :plugins, :load_plugins, :locate_plugins
 
@@ -255,6 +259,7 @@ class Pry
     @cli = false
     @current_line = 0
     @line_buffer = []
+    @eval_path = "(pry)"
   end
 
   # Basic initialization.

lib/pry/pry_instance.rb

@@ -187,7 +187,7 @@ class Pry
     expr = r(target)
 
     Pry.line_buffer.push(*expr.each_line)
-    set_last_result(target.eval(expr, "(pry)", Pry.current_line), target)
+    set_last_result(target.eval(expr, Pry.eval_path, Pry.current_line), target)
   rescue SystemExit => e
     exit
   rescue Exception => e