Fix for issue jruby#276

This commit fixes issue jruby#276 which is a regression introduced by
http://jira.codehaus.org/browse/JRUBY-6729.  The bug was caused by a erroneous
behavour when yielding splat for a block of arity of one: MRI doesn't unsplat
the passed value, whilst jruby was.

See GH-276_yield_splat_behaviour_causes_pp_to_break.rb for details on behaviour

spec/regression/GH-276_yield_splat_behaviour_causes_pp_to_break.rb

@@ -0,0 +1,55 @@
+require 'rspec'
+
+def call_one
+  yield(["a"])
+end
+
+def call_two
+  yield(["a","b"])
+end
+
+def call_three
+  yield(["a", "b", "c"])
+end
+
+def yield_with_splat(method_name = 'call_two')
+  send(method_name) { |*a| yield(*a) }
+end
+
+describe 'yield splat' do
+  it 'yields an array when block has only one argument' do
+    value = nil
+    yield_with_splat("call_one") { |a| value = a }
+    value.should == ["a"]
+  end
+
+  it 'yields an array when block as one argument and passed two' do
+    value = nil
+    yield_with_splat("call_two") { |a| value = a }
+    value.should == ["a", "b"]
+  end
+
+  it 'yields one value when block has two arguments and passed one' do
+    first_value = nil
+    second_value = nil
+    yield_with_splat("call_one") { |a,b| first_value = a; second_value = b }
+    first_value.should == "a"
+    second_value.should == nil
+  end
+
+  it 'yields two values when block has two arguments and passed two' do
+    first_value = nil
+    second_value = nil
+    yield_with_splat { |a,b| first_value = a; second_value = b }
+    first_value.should == "a"
+    second_value.should == "b"
+  end
+
+  it 'yields two values when block has two arguments and passed three' do
+    first_value = nil
+    second_value = nil
+    yield_with_splat("call_three") { |a,b| first_value = a; second_value = b }
+    first_value.should == "a"
+    second_value.should == "b"
+  end
+end

src/org/jruby/ast/Yield19Node.java

@@ -24,12 +24,13 @@ public Yield19Node(ISourcePosition position, Node node) {
     public IRubyObject interpret(Ruby runtime, ThreadContext context, IRubyObject self, Block aBlock) {
         Node args = getArgsNode();
         IRubyObject argsResult = args.interpret(runtime, context, self, aBlock);
+        Block yieldToBlock = context.getCurrentFrame().getBlock();
 
         switch (args.getNodeType()) {
             case ARGSPUSHNODE:
             case ARGSCATNODE:
             case SPLATNODE: 
-                argsResult = RuntimeHelpers.unsplatValue19(argsResult);
+                if (yieldToBlock.arity().getValue() > 1) argsResult = RuntimeHelpers.unsplatValue19(argsResult);
                 break;
             case ARRAYNODE:
                 // Pass-thru
@@ -38,6 +39,6 @@ public IRubyObject interpret(Ruby runtime, ThreadContext context, IRubyObject se
                assert false: "Invalid node found in yield";
         }
 
-        return context.getCurrentFrame().getBlock().yieldArray(context, argsResult, null, null);
+        return yieldToBlock.yieldArray(context, argsResult, null, null);
     }
 }

src/org/jruby/javasupport/util/RuntimeHelpers.java

@@ -1820,8 +1820,7 @@ public static IRubyObject unsplatValue19(IRubyObject argsResult) {
 
             if (array.size() == 1) {
                 IRubyObject newResult = array.eltInternal(0);
-                // JRUBY-6729. It seems RubyArray should be returned as it is from here.
-                if (!(newResult instanceof RubyArray)) {
+                if (!((newResult instanceof RubyArray) && ((RubyArray) newResult).size() == 0)) {
                     argsResult = newResult;
                 }
             }

test/externals/ruby1.9/test_pp.rb

@@ -137,6 +137,12 @@ def test_hash
     assert_equal("#{a.inspect}\n", PP.pp(a, ''))
   end
 
+  def test_hash_with_boolean_value
+    a = {}
+    a[:b] = true
+    assert_equal("{:b=>true}\n", PP.pp(a,''))
+  end
+
   S = Struct.new("S", :a, :b)
   def test_struct
     a = S.new(1,2)