9032 Fix Different arguments for each.map vs each and map alone

Author: evaniainbrooks

core/src/main/java/org/jruby/RubyEnumerator.java

@@ -324,7 +324,14 @@ private IRubyObject __each__(ThreadContext context, final Block block) {
         if (methodArgsHasKeywords) context.callInfo = CALL_KEYWORD;
         return object.callMethod(context, method, methodArgs,
                 CallBlock.newCallClosure(context, this, Signature.OPTIONAL, (ctx, args, blk) -> {
-                    IRubyObject ret = block.yieldValues(ctx, args);
+                    IRubyObject ret;
+
+                    if (args.length == 1) {
+                        ret = block.yield(ctx, args[0]);
+                    } else {
+                        ret = block.yieldValues(ctx, args);
+                    }
+
                     IRubyObject val = feedValue.use_value(ctx);
                     return val.isNil() ? ret : val;
                 })

spec/ruby/core/enumerator/each_spec.rb

@@ -86,4 +86,19 @@ def object_each_with_arguments.each_with_arguments(arg, *args)
     ret.should be_an_instance_of(Enumerator)
     ret.should_not equal(@enum_with_arguments)
   end
+
+  it "does not destructure yielded array values when chaining each.map" do
+    result = [[[1]]].each.map { |a, b| [a, b] }
+    result.should == [[[1], nil]]
+  end
+
+  it "preserves array values yielded from the enumerator" do
+    result = [[1, 2]].each.map { |a| a }
+    result.should == [[1, 2]]
+  end
+
+  it "allows destructuring to occur in the block, not the enumerator" do
+    result = [[1, 2]].each.map { |a, b| a }
+    result.should == [1]
+  end
 end