✨ Expose failing JToken in ValidationError (#1692)

Exposing the JToken that failed the error will allow NJsonSchema to better leverage validation errors by accessing the value that failed the schema.

src/NJsonSchema.Tests/Validation/ObjectValidationTests.cs

@@ -24,6 +24,7 @@ public void When_token_is_not_object_then_validation_should_fail()
 
             //// Assert
             Assert.Equal(ValidationErrorKind.ObjectExpected, errors.First().Kind);
+            Assert.Equal("10", errors.First().Token?.ToString());
         }
 
         [Fact]
@@ -47,6 +48,7 @@ public void When_required_property_is_missing_then_it_should_be_in_error_list()
             Assert.Equal("Foo", errors.First().Property);
             Assert.Equal("#/Foo", errors.First().Path);
             Assert.Equal(ValidationErrorKind.PropertyRequired, errors.First().Kind);
+            Assert.Equal("{}", errors.First().Token?.ToString());
         }
 
         [Fact]
@@ -134,6 +136,7 @@ public void When_string_property_required_but_integer_provided_then_it_should_fa
             Assert.Equal(ValidationErrorKind.StringExpected, errors.First().Kind);
             Assert.Equal("Foo", errors.First().Property);
             Assert.Equal("#/Foo", errors.First().Path);
+            Assert.Equal("10", errors.First().Token?.ToString());
         }
 
         [Fact]
@@ -180,6 +183,7 @@ public void When_case_sensitive_and_property_has_different_casing_then_it_should
 
             //// Assert
             Assert.Equal(ValidationErrorKind.NoAdditionalPropertiesAllowed, errors.First().Kind);
+            Assert.Equal("\"foo\": 5", errors.First().Token?.ToString());
         }
 
         [Fact]

src/NJsonSchema/Validation/ValidationError.cs

@@ -25,6 +25,7 @@ public ValidationError(ValidationErrorKind errorKind, string? propertyName, stri
             Kind = errorKind;
             Property = propertyName;
             Path = propertyPath != null ? "#/" + propertyPath : "#";
+            Token = token;
 
             var lineInfo = token as IJsonLineInfo;
             HasLineInfo = lineInfo != null && lineInfo.HasLineInfo();
@@ -63,6 +64,9 @@ public ValidationError(ValidationErrorKind errorKind, string? propertyName, stri
         /// <summary>Gets the schema element that contains the validation rule. </summary>
         public JsonSchema Schema { get; private set; }
 
+        /// <summary>Gets the JToken of the element failed the validation. </summary>
+        public JToken? Token { get; private set; }
+
         /// <summary>Returns a string that represents the current object.</summary>
         /// <returns>A string that represents the current object.</returns>
         /// <filterpriority>2</filterpriority>