Fix lambda function Zip type attribute checks

.changelog/20575.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_lambda_function: Fix `handler`, `runtime` attribute validation for `package_type` is `Zip`
+```

aws/resource_aws_lambda_function.go

@@ -332,7 +332,7 @@ func checkHandlerRuntimeForZipFunction(_ context.Context, d *schema.ResourceDiff
 	_, handlerOk := d.GetOk("handler")
 	_, runtimeOk := d.GetOk("runtime")
 
-	if packageType == lambda.PackageTypeZip && !handlerOk && !runtimeOk {
+	if packageType == lambda.PackageTypeZip && (!handlerOk || !runtimeOk) {
 		return fmt.Errorf("handler and runtime must be set when PackageType is Zip")
 	}
 	return nil

aws/resource_aws_lambda_function_test.go

@@ -1865,6 +1865,31 @@ func TestAccAWSLambdaFunction_runtimes(t *testing.T) {
 	})
 }
 
+func TestAccAWSLambdaFunction_zip_validation(t *testing.T) {
+	rString := acctest.RandString(8)
+	funcName := fmt.Sprintf("tf_acc_lambda_func_expect_%s", rString)
+	policyName := fmt.Sprintf("tf_acc_policy_lambda_func_expect_%s", rString)
+	roleName := fmt.Sprintf("tf_acc_role_lambda_func_expect_%s", rString)
+	sgName := fmt.Sprintf("tf_acc_sg_lambda_func_expect_%s", rString)
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		ErrorCheck:   testAccErrorCheck(t, lambda.EndpointsID),
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckLambdaFunctionDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config:      testAccAWSLambdaZipConfigWithoutHandler(funcName, policyName, roleName, sgName),
+				ExpectError: regexp.MustCompile("handler and runtime must be set when PackageType is Zip"),
+			},
+			{
+				Config:      testAccAWSLambdaZipConfigWithoutRuntime(funcName, policyName, roleName, sgName),
+				ExpectError: regexp.MustCompile("handler and runtime must be set when PackageType is Zip"),
+			},
+		},
+	})
+}
+
 func testAccCheckLambdaFunctionDestroy(s *terraform.State) error {
 	conn := testAccProvider.Meta().(*AWSClient).lambdaconn
 
@@ -3305,6 +3330,26 @@ resource "aws_lambda_function" "test" {
 `, rName, runtime))
 }
 
+func testAccAWSLambdaZipConfigWithoutHandler(funcName, policyName, roleName, sgName string) string {
+	return fmt.Sprintf(baseAccAWSLambdaConfig(policyName, roleName, sgName)+`
+resource "aws_lambda_function" "test" {
+  function_name = "%s"
+  role          = aws_iam_role.iam_for_lambda.arn
+  runtime       = "nodejs12.x"
+}
+`, funcName)
+}
+
+func testAccAWSLambdaZipConfigWithoutRuntime(funcName, policyName, roleName, sgName string) string {
+	return fmt.Sprintf(baseAccAWSLambdaConfig(policyName, roleName, sgName)+`
+resource "aws_lambda_function" "test" {
+  function_name = "%s"
+  role          = aws_iam_role.iam_for_lambda.arn
+  handler       = "exports.example"
+}
+`, funcName)
+}
+
 func TestFlattenLambdaImageConfigShouldNotFailWithEmptyImageConfig(t *testing.T) {
 	t.Parallel()
 	response := lambda.ImageConfigResponse{}