Add enum value validation in input object

validator/testdata/vars.graphql

@@ -18,10 +18,15 @@ input InputType {
     name: String!
     nullName: String
     nullEmbedded: Embedded
+    enum: Enum
 }
 
 input Embedded {
     name: String!
 }
 
+enum Enum {
+    A
+}
+
 scalar Custom

validator/vars.go

@@ -2,6 +2,7 @@ package validator
 
 import (
 	"reflect"
+	"strings"
 
 	"fmt"
 
@@ -117,10 +118,19 @@ func (v *varValidator) validateVarType(typ *ast.Type, val reflect.Value) *gqlerr
 	switch def.Kind {
 	case ast.Enum:
 		kind := val.Type().Kind()
-		if kind == reflect.Int || kind == reflect.Int32 || kind == reflect.Int64 || kind == reflect.String {
-			return nil
+		if kind != reflect.Int && kind != reflect.Int32 && kind != reflect.Int64 && kind != reflect.String {
+			return gqlerror.ErrorPathf(v.path, "enums must be ints or strings")
+		}
+		isValidEnum := false
+		for _, enumVal := range def.EnumValues {
+			if strings.EqualFold(val.String(), enumVal.Name) {
+				isValidEnum = true
+			}
 		}
-		return gqlerror.ErrorPathf(v.path, "enums must be ints or strings")
+		if !isValidEnum {
+			return gqlerror.ErrorPathf(v.path, "%s is not a valid %s", val.String(), def.Name)
+		}
+		return nil
 	case ast.Scalar:
 		kind := val.Type().Kind()
 		switch typ.NamedType {

validator/vars_test.go

@@ -126,6 +126,28 @@ func TestValidateVars(t *testing.T) {
 			})
 			require.EqualError(t, gerr, "input: variable.var.foobard unknown field")
 		})
+
+		t.Run("enum input object", func(t *testing.T) {
+			q := gqlparser.MustLoadQuery(schema, `query foo($var: InputType!) { structArg(i: $var) }`)
+			_, gerr := validator.VariableValues(schema, q.Operations.ForName(""), map[string]interface{}{
+				"var": map[string]interface{}{
+					"name": "foobar",
+					"enum": "A",
+				},
+			})
+			require.Nil(t, gerr)
+		})
+
+		t.Run("unknown enum value input object", func(t *testing.T) {
+			q := gqlparser.MustLoadQuery(schema, `query foo($var: InputType!) { structArg(i: $var) }`)
+			_, gerr := validator.VariableValues(schema, q.Operations.ForName(""), map[string]interface{}{
+				"var": map[string]interface{}{
+					"name": "foobar",
+					"enum": "B",
+				},
+			})
+			require.EqualError(t, gerr, "input: variable.var.enum B is not a valid Enum")
+		})
 	})
 
 	t.Run("array", func(t *testing.T) {