handle Rhino's 64K code generation (method) limit on the fly

simple retry running the failed compilation in interpreter mode

lib/rhino/context.rb

@@ -240,16 +240,21 @@ module Rhino
     alias :version= :javascript_version= 
     
     # Enter this context for operations. 
-    # Some methods such as eval() will fail unless this context is open !
+    # Some methods such as eval() will fail unless the context is open.
     def open(&block)
       do_open(&block)
     rescue JS::RhinoException => e
+      if code_generation_error?(e)
+        warn "[INFO] Rhino byte-code generation failed forcing #{@native} into interpreted mode"
+        self.optimization_level = -1
+        retry
+      end
       raise Rhino::JSError.new(e)
     end
     
     private
     
-      def do_open
+    def do_open # :nodoc
       factory.enterContext(@native)
       begin
         yield self
@@ -258,6 +263,33 @@ module Rhino
       end
     end
     
+    CODE_GENERATION_ERROR_MESSAGE = 'generated bytecode for method exceeds 64K limit' # :nodoc
+
+    CODE_GENERATION_TRACE_CLASS_NAME = 'org.mozilla.javascript.optimizer.Codegen' # :nodoc
+    CODE_GENERATION_TRACE_METHOD_NAME = 'reportClassFileFormatException' # :nodoc
+    # at org.mozilla.javascript.optimizer.Codegen.reportClassFileFormatException
+
+    def code_generation_error?(exception) # :nodoc
+      if ( exception.is_a?(NativeException) rescue nil ) # JRuby 1.6 wrapping
+        exception = exception.cause
+      end
+      if exception.class == Rhino::JS::EvaluatorException
+        if exception.message.index(CODE_GENERATION_ERROR_MESSAGE)
+          return true
+        end
+        # NOTE: unfortunately Rhino localizes the error messages!
+        # and the ClassFileFormatException is not kept as a cause
+        class_name = CODE_GENERATION_TRACE_CLASS_NAME
+        method_name = CODE_GENERATION_TRACE_METHOD_NAME
+        for trace in exception.getStackTrace()
+          if class_name == trace.class_name && method_name == trace.method_name
+            return true
+          end
+        end
+      end
+      false
+    end
+
   end
 
   class IOReader < java.io.Reader # :nodoc:

spec/rhino/context_spec.rb

@@ -166,4 +166,19 @@ describe Rhino::Context do
     end
   end
 
+  it "handles code generation error when 'generated bytecode for method exceeds 64K limit'" do
+    context = Rhino::Context.new
+    
+    big_script = ''
+    10000.times { |i| big_script << "var s#{i} = '#{i}';\n" }
+    10000.times { |i| big_script << "var n#{i} = +#{i} ;\n" }
+
+    lambda {
+      context.eval big_script
+    }.should_not raise_error
+
+    context.eval('( s9999 )').should == '9999'
+    context.eval('( n9999 )').should == +9999
+  end
+
 end