Refactor invalid operation exception handling (#87)

Addresses part of #80

Author: jbagga

src/Microsoft.AspNetCore.JsonPatch/Operations/OperationBase.cs

@@ -2,34 +2,45 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using Microsoft.AspNetCore.JsonPatch.Exceptions;
 using Newtonsoft.Json;
 
 namespace Microsoft.AspNetCore.JsonPatch.Operations
 {
     public class OperationBase
     {
+        private string _op;
+        private OperationType _operationType;
+
         [JsonIgnore]
         public OperationType OperationType
         {
             get
             {
-                OperationType result;
-                if (!Enum.TryParse(op, ignoreCase: true, result: out result))
-                {
-                    throw new JsonPatchException(
-                        Resources.FormatInvalidJsonPatchOperation(op),
-                        innerException: null);
-                }
-                return result;
+                return _operationType;
             }
         }
 
         [JsonProperty("path")]
         public string path { get; set; }
 
         [JsonProperty("op")]
-        public string op { get; set; }
+        public string op
+        {
+            get
+            {
+                return _op;
+            }
+            set
+            {
+                OperationType result;
+                if (!Enum.TryParse(value, ignoreCase: true, result: out result))
+                {
+                    result = OperationType.Invalid;
+                }
+                _operationType = result;
+                _op = value;
+            }
+        }
 
         [JsonProperty("from")]
         public string from { get; set; }

src/Microsoft.AspNetCore.JsonPatch/Operations/OperationOfT.cs

@@ -75,6 +75,9 @@ public void Apply(TModel objectToApplyTo, IObjectAdapter adapter)
                     break;
                 case OperationType.Test:
                     throw new JsonPatchException(new JsonPatchError(objectToApplyTo, this, Resources.TestOperationNotSupported));
+                case OperationType.Invalid:
+                    throw new JsonPatchException(
+                        Resources.FormatInvalidJsonPatchOperation(op), innerException: null);
                 default:
                     break;
             }

src/Microsoft.AspNetCore.JsonPatch/Operations/OperationType.cs

@@ -10,6 +10,7 @@ public enum OperationType
         Replace,
         Move,
         Copy,
-        Test
+        Test,
+        Invalid
     }
 }

test/Microsoft.AspNetCore.JsonPatch.Test/OperationBaseTests.cs

@@ -0,0 +1,41 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Xunit;
+
+namespace Microsoft.AspNetCore.JsonPatch.Operations
+{
+    public class OperationBaseTests
+    {
+        [Theory]
+        [InlineData("ADd", OperationType.Add)]
+        [InlineData("Copy", OperationType.Copy)]
+        [InlineData("mOVE", OperationType.Move)]
+        [InlineData("REMOVE", OperationType.Remove)]
+        [InlineData("replace", OperationType.Replace)]
+        [InlineData("TeSt", OperationType.Test)]
+        public void SetValidOperationType(string op, OperationType operationType)
+        {
+            // Arrange
+            var operationBase = new OperationBase();
+            operationBase.op = op;
+
+            // Act & Assert
+            Assert.Equal(operationType, operationBase.OperationType);
+        }
+
+        [Theory]
+        [InlineData("invalid", OperationType.Invalid)]
+        [InlineData("coppy", OperationType.Invalid)]
+        [InlineData("notvalid", OperationType.Invalid)]
+        public void InvalidOperationType_SetsOperationTypeInvalid(string op, OperationType operationType)
+        {
+            // Arrange
+            var operationBase = new OperationBase();
+            operationBase.op = op;
+
+            // Act & Assert
+            Assert.Equal(operationType, operationBase.OperationType);
+        }
+    }
+}