Skip server-side JS if no components were rendered

Fixes reactjs#821

Author: Dustin Masters

src/React.Core/ReactEnvironment.cs

@@ -332,7 +332,7 @@ public virtual string GetInitJavaScript(bool clientOnly = false)
 		public virtual void GetInitJavaScript(TextWriter writer, bool clientOnly = false)
 		{
 			// Propagate any server-side console.log calls to corresponding client-side calls.
-			if (!clientOnly)
+			if (!clientOnly && _components.Count != 0)
 			{
 				var consoleCalls = Execute<string>("console.getCalls()");
 				writer.Write(consoleCalls);

tests/React.Tests/Core/ReactEnvironmentTest.cs

@@ -136,6 +136,24 @@ public void ServerSideOnlyComponentRendersNoJavaScript()
 			Assert.Equal(string.Empty, environment.GetInitJavaScript());
 		}
 
+		[Theory]
+		[InlineData(false, 0)]
+		[InlineData(true, 1)]
+		public void SSRInitSkippedIfNoComponents(bool renderComponent, int ssrTimes)
+		{
+			var mocks = new Mocks();
+			var environment = mocks.CreateReactEnvironment();
+
+			if (renderComponent)
+			{
+				environment.CreateComponent("HelloWorld", new { name = "Daniel" }, clientOnly: true).RenderHtml();
+			}
+
+			environment.GetInitJavaScript();
+
+			mocks.Engine.Verify(x => x.Evaluate<string>("console.getCalls()"), Times.Exactly(ssrTimes));
+		}
+
 		public class Mocks
 		{
 			public Mock<PooledJsEngine> Engine { get; private set; }