From b93e94c0c38b954e16cf775f7f1d1cd60cbfd703 Mon Sep 17 00:00:00 2001
From: Robbie Averill <robbie@silverstripe.com>
Date: Mon, 25 Jun 2018 11:06:43 +1200
Subject: [PATCH] FIX FormField::Link now throws a LogicException if no form is
 set yet

---
 src/Forms/FormField.php           | 11 +++++++++--
 tests/php/Forms/FormFieldTest.php | 18 ++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/Forms/FormField.php b/src/Forms/FormField.php
index 8b6c3a571..502163b0b 100644
--- a/src/Forms/FormField.php
+++ b/src/Forms/FormField.php
@@ -2,6 +2,7 @@
 
 namespace SilverStripe\Forms;
 
+use LogicException;
 use ReflectionClass;
 use SilverStripe\Control\Controller;
 use SilverStripe\Control\RequestHandler;
@@ -355,14 +356,20 @@ class FormField extends RequestHandler
     }
 
     /**
-     * Return a link to this field.
+     * Return a link to this field
      *
      * @param string $action
-     *
      * @return string
+     * @throws LogicException If no form is set yet
      */
     public function Link($action = null)
     {
+        if (!$this->form) {
+            throw new LogicException(
+                'Field must be associated with a form to call Link(). Please use $field->setForm($form);'
+            );
+        }
+
         $link = Controller::join_links($this->form->FormAction(), 'field/' . $this->name, $action);
         $this->extend('updateLink', $link, $action);
         return $link;
diff --git a/tests/php/Forms/FormFieldTest.php b/tests/php/Forms/FormFieldTest.php
index 07c5d618e..b63cbec76 100644
--- a/tests/php/Forms/FormFieldTest.php
+++ b/tests/php/Forms/FormFieldTest.php
@@ -384,4 +384,22 @@ class FormFieldTest extends SapphireTest
         $this->assertFalse($field->hasClass('banana'));
         $this->assertTrue($field->hasClass('cool-BAnana'));
     }
+
+    public function testLinkWithForm()
+    {
+        $field = new FormField('Test');
+        $form = new Form(null, 'Test', new FieldList, new FieldList);
+        $form->setFormAction('foo');
+        $field->setForm($form);
+        $this->assertSame('foo/field/Test/bar', $field->Link('bar'));
+    }
+
+    /**
+     * @expectedException \LogicException
+     */
+    public function testLinkWithoutForm()
+    {
+        $field = new FormField('Test');
+        $field->Link('bar');
+    }
 }