Fix for incorrect reporting of a type mismatch when object mapping fails and a Vector type is involved. (#871)

* Fix for incorrect reporting of a type mismatch when object mapping fails and a Vector type is involved.
Before the fix the error reported when trying to map from, for example, a Vector<float> to a Vector<double> was:
System.InvalidOperationException: The expected value `Neo4j.Driver.Vector`1[System.Single]` is different from the actual value `System.Collections.Generic.List`1[System.Single]`

This was occurring because the ValueExtensions As method did not contain a clause for IVector, this caused the logic to fall through to the IEnumerable clause (which a vector implements) which converted the vector into a list, and then failed the type conversion on that list.

Now that a clause for IVector is added you get the correct error. e.g. For the Vector<float> -> Vector<double> example:
System.InvalidOperationException: The expected value `Neo4j.Driver.Vector`1[System.Single]` is different from the actual value `Neo4j.Driver.Vector`1[System.Double]`

* Added tests to check on vector conversions in the valueExtensions class. Vectors should not be able to be converted to any other type, or between mismatched vectors.

Author: AndyHeap-NeoTech

Neo4j.Driver/Neo4j.Driver.Tests/ValueExtensionsTests.cs

@@ -236,6 +236,30 @@ public void ShouldThrowExceptionWhenCastFromListToInt()
             var ex = Record.Exception(() => value.As<int>());
             ex.Should().BeOfType<InvalidCastException>();
         }
+
+        [Fact]
+        public void ShouldThrowExceptionWhenCastFromVectorToNonVector()
+        {
+            object value = new Vector<float>(new[] { 1.0f, 2.0f, 3.0f, 4.0f });
+            var ex = Record.Exception(() => value.As<int>());
+            ex.Should().BeOfType<InvalidCastException>();
+        }
+
+        [Fact]
+        public void ShouldThrowExceptionWhenCastFromNonVectorToVector()
+        {
+            object value = (int)10;
+            var ex = Record.Exception(() => value.As<Vector<int>>());
+            ex.Should().BeOfType<InvalidCastException>();
+        }
+
+        [Fact]
+        public void ShouldThrowExceptionWhenCastingBetweenMismatchedVectors()
+        {
+            object value = new Vector<float>(new[] { 1.0f, 2.0f, 3.0f, 4.0f });
+            var ex = Record.Exception(() => value.As<Vector<double>>());
+            ex.Should().BeOfType<InvalidCastException>();
+        }
     }
 
     public class AsCollectionTypeMethod

Neo4j.Driver/Neo4j.Driver/Public/Extensions/ValueExtensions.cs

@@ -149,6 +149,13 @@ public static T As<T>(this object value)
         {
             return Convert.ChangeType(value, targetType).AsItIs<T>();
         }
+        
+        //If the source type (value) is a vector then it can not be cast to anything else. We also want to 
+        //make sure that it is not attempting to cast into a vector of another type. 
+        if (value is IVector)
+        {
+            return AsVector<T>(value);
+        }                
 
         // force to cast to a dict or list
         var typeInfo = targetType.GetTypeInfo();
@@ -197,6 +204,17 @@ private static T AsList<T>(this IEnumerable value, TypeInfo typeInfo)
         return list.AsItIs<T>();
     }
 
+    private static T AsVector<T>(this object value)
+    {   
+        if (value is T result)
+        {
+            return result;
+        }
+        
+        throw new InvalidCastException($"Cannot cast differing vector types. Attempting from `" +
+            $" { typeof(T) }` to `{value.GetType()}");
+    }
+
 #region Helper Methods
 
     private static object InvokeStatic(this MethodInfo method, params object[] parameters)