Enhance check for value types to exclude Nullable

The System.Nullable type is a value type that can be assigned
the null value. This change checks for types wrapped with
Nullable and does not throw when they are encountered.

Fixes #1316

Signed-off-by: Jim Evans <james.h.evans.jr@gmail.com>

Author: chrisblock

dotnet/src/support/Extensions/WebDriverExtensions.cs

@@ -91,7 +91,7 @@ public static T ExecuteJavaScript<T>(this IWebDriver driver, string script, para
             object value = executor.ExecuteScript(script, args);
             if (value == null)
             {
-                if (type.IsValueType)
+                if (type.IsValueType && (Nullable.GetUnderlyingType(type) == null))
                 {
                     throw new WebDriverException("Script returned null, but desired type is a value type");
                 }

dotnet/test/support/Extensions/ExecuteJavaScriptTest.cs

@@ -112,6 +112,17 @@ public void ShouldNotThrowWhenNullIsReturned()
             Assert.That(() => driver.ExecuteJavaScript<string>(JavaScript, JavaScriptParameters), Throws.Nothing);
         }
 
+        [Test]
+        public void ShouldNotThrowWhenNullIsReturnedForNullableValueType()
+        {
+            Expect.Once.On(driver)
+                .Method("ExecuteScript")
+                .With(JavaScript, JavaScriptParameters)
+                .Will(Return.Value(null));
+
+            Assert.That(() => driver.ExecuteJavaScript<int?>(JavaScript, JavaScriptParameters), Throws.Nothing);
+        }
+
         [Test]
         public void ShouldThrowWhenNullIsReturnedForValueType()
         {