From 9c61a55fea25f81efd99005225bc83156938498e Mon Sep 17 00:00:00 2001
From: Javier Eguiluz <javier.eguiluz@gmail.com>
Date: Mon, 2 Jul 2018 17:36:11 +0200
Subject: [PATCH 1/4] Made the code of a validation example more robust

---
 validation/custom_constraint.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/validation/custom_constraint.rst b/validation/custom_constraint.rst
index 2430143dd0e..c401a161ea1 100644
--- a/validation/custom_constraint.rst
+++ b/validation/custom_constraint.rst
@@ -59,11 +59,16 @@ The validator class is also simple, and only has one required method ``validate(
 
     use Symfony\Component\Validator\Constraint;
     use Symfony\Component\Validator\ConstraintValidator;
+    use Symfony\Component\Validator\Exception\UnexpectedTypeException;
 
     class ContainsAlphanumericValidator extends ConstraintValidator
     {
         public function validate($value, Constraint $constraint)
         {
+            if (!is_string($value) && !(is_object($value) && method_exists($value, '__toString'))) {
+                throw new UnexpectedTypeException($value, 'string');
+            }
+
             if (!preg_match('/^[a-zA-Z0-9]+$/', $value, $matches)) {
                 // If you're using the new 2.5 validation API (you probably are!)
                 $this->context->buildViolation($constraint->message)

From cc0e6b89a90818ca205b3c6a232af94db176de8e Mon Sep 17 00:00:00 2001
From: Javier Eguiluz <javier.eguiluz@gmail.com>
Date: Tue, 3 Jul 2018 11:00:02 +0200
Subject: [PATCH 2/4] Added a check for empty strings

---
 validation/custom_constraint.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/validation/custom_constraint.rst b/validation/custom_constraint.rst
index c401a161ea1..130b69371e1 100644
--- a/validation/custom_constraint.rst
+++ b/validation/custom_constraint.rst
@@ -69,6 +69,10 @@ The validator class is also simple, and only has one required method ``validate(
                 throw new UnexpectedTypeException($value, 'string');
             }
 
+            if ('' === $value) {
+                return;
+            }
+
             if (!preg_match('/^[a-zA-Z0-9]+$/', $value, $matches)) {
                 // If you're using the new 2.5 validation API (you probably are!)
                 $this->context->buildViolation($constraint->message)

From f202e6d7146456d7d842137f33c770c3b9889459 Mon Sep 17 00:00:00 2001
From: Javier Eguiluz <javier.eguiluz@gmail.com>
Date: Tue, 3 Jul 2018 15:49:02 +0200
Subject: [PATCH 3/4] Refactored the code

---
 validation/custom_constraint.rst | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/validation/custom_constraint.rst b/validation/custom_constraint.rst
index 130b69371e1..12faa364d1e 100644
--- a/validation/custom_constraint.rst
+++ b/validation/custom_constraint.rst
@@ -65,12 +65,12 @@ The validator class is also simple, and only has one required method ``validate(
     {
         public function validate($value, Constraint $constraint)
         {
-            if (!is_string($value) && !(is_object($value) && method_exists($value, '__toString'))) {
-                throw new UnexpectedTypeException($value, 'string');
+            if (null === $value || '' === $value) {
+                return;
             }
 
-            if ('' === $value) {
-                return;
+            if (!is_string($value)) {
+                throw new UnexpectedTypeException($value, 'string');
             }
 
             if (!preg_match('/^[a-zA-Z0-9]+$/', $value, $matches)) {

From c7ac3f749fa54c6b6c6eddc76b916e2c16900c7a Mon Sep 17 00:00:00 2001
From: Javier Eguiluz <javier.eguiluz@gmail.com>
Date: Tue, 3 Jul 2018 17:32:33 +0200
Subject: [PATCH 4/4] Added a comment to explain why you should do this

---
 validation/custom_constraint.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/validation/custom_constraint.rst b/validation/custom_constraint.rst
index 12faa364d1e..f67b3630276 100644
--- a/validation/custom_constraint.rst
+++ b/validation/custom_constraint.rst
@@ -65,6 +65,8 @@ The validator class is also simple, and only has one required method ``validate(
     {
         public function validate($value, Constraint $constraint)
         {
+            // custom constraints should ignore null and empty values to allow
+            // other constraints (NotBlank, NotNull, etc.) take care of that
             if (null === $value || '' === $value) {
                 return;
             }