Move the superuser/password validation to CustomizeDiff func

redshift/resource_redshift_user.go

@@ -1,6 +1,7 @@
 package redshift
 
 import (
+	"context"
 	"crypto/md5"
 	"database/sql"
 	"fmt"
@@ -54,6 +55,15 @@ Amazon Redshift user accounts can only be created and dropped by a database supe
 		Importer: &schema.ResourceImporter{
 			State: schema.ImportStatePassthrough,
 		},
+		CustomizeDiff: func(_ context.Context, d *schema.ResourceDiff, p interface{}) error {
+			isSuperuser := d.Get(userSuperuserAttr).(bool)
+			password, hasPassword := d.GetOk(userPasswordAttr)
+			if isSuperuser && (!hasPassword || password.(string) == "") {
+				return fmt.Errorf("Users that are superusers must define a password.")
+			}
+
+			return nil
+		},
 
 		Schema: map[string]*schema.Schema{
 			userNameAttr: {
@@ -109,7 +119,6 @@ Amazon Redshift user accounts can only be created and dropped by a database supe
 			},
 			userSuperuserAttr: {
 				ConflictsWith: []string{userSyslogAccessAttr},
-				RequiredWith:  []string{userPasswordAttr},
 				Type:          schema.TypeBool,
 				Optional:      true,
 				Default:       false,

redshift/resource_redshift_user_test.go

@@ -201,7 +201,28 @@ resource "redshift_user" "superuser" {
 		Steps: []resource.TestStep{
 			{
 				Config:      config,
-				ExpectError: regexp.MustCompile("\"superuser\": all of `password,superuser` must be specified"),
+				ExpectError: regexp.MustCompile("Users that are superusers must define a password."),
+			},
+		},
+	})
+}
+
+func TestAccRedshiftUser_SuperuserFalseDoesntRequiresPassword(t *testing.T) {
+	userName := strings.ReplaceAll(acctest.RandomWithPrefix("tf_acc_superuser"), "-", "_")
+	config := fmt.Sprintf(`
+resource "redshift_user" "superuser" {
+  name = %[1]q
+  superuser = false
+}
+`, userName)
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckRedshiftUserDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: config,
 			},
 		},
 	})