FIX Don't load data up front for lazy-loaded searchable dropdown (#11278)

src/Forms/SearchableDropdownField.php

@@ -9,7 +9,7 @@ use SilverStripe\ORM\DataList;
 class SearchableDropdownField extends DropdownField
 {
     use SearchableDropdownTrait;
-    
+
     // This needs to be defined on the class, not the trait, otherwise there is a PHP error
     protected $schemaComponent = 'SearchableDropdownField';
 

src/Forms/SearchableDropdownTrait.php

@@ -265,6 +265,13 @@ trait SearchableDropdownTrait
         return $this->getListMap($this->sourceList);
     }
 
+    public function Field($properties = [])
+    {
+        $context = $this;
+        $this->extend('onBeforeRender', $context, $properties);
+        return $context->customise($properties)->renderWith($context->getTemplates());
+    }
+
     /*
      * @param mixed $source
      */
@@ -450,9 +457,16 @@ trait SearchableDropdownTrait
 
     public function getSchemaStateDefaults(): array
     {
-        $data = parent::getSchemaStateDefaults();
+        $state = [
-        $data = $this->updateDataForSchema($data);
+            'name' => $this->getName(),
-        return $data;
+            'id' => $this->ID(),
+            'value' => $this->getDefaultSchemaValue(),
+            'message' => $this->getSchemaMessage(),
+            'data' => [],
+        ];
+
+        $state = $this->updateDataForSchema($state);
+        return $state;
     }
 
     /**
@@ -467,6 +481,14 @@ trait SearchableDropdownTrait
         return $this;
     }
 
+    private function getDefaultSchemaValue()
+    {
+        if (!$this->getIsLazyLoaded() && $this->hasMethod('getDefaultValue')) {
+            return $this->getDefaultValue();
+        }
+        return $this->Value();
+    }
+
     private function getOptionsForSearchRequest(string $term): array
     {
         if (!$this->sourceList) {

tests/php/Forms/SearchableDropdownTraitTest.php

@@ -3,6 +3,7 @@
 namespace SilverStripe\Forms\Tests;
 
 use SilverStripe\Control\HTTPRequest;
+use SilverStripe\Core\ClassInfo;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Forms\FieldList;
 use SilverStripe\Forms\SearchableDropdownField;
@@ -217,4 +218,47 @@ class SearchableDropdownTraitTest extends SapphireTest
         $this->assertSame('My placeholder', $schema['placeholder']);
         $this->assertFalse($schema['searchable']);
     }
+
+    public function provideLazyLoadedDoesntCallGetSource()
+    {
+        $methodsToCall = [
+            'Field',
+            'getSchemaStateDefaults',
+            'getSchemaState',
+            'getSchemaDataDefaults',
+            'getSchemaData',
+        ];
+        $classes = [
+            SearchableMultiDropdownField::class,
+            SearchableDropdownField::class,
+        ];
+        $scenarios = [];
+        foreach ($classes as $class) {
+            foreach ($methodsToCall as $method) {
+                $scenarios[] = [
+                    'fieldClass' => $class,
+                    'methodToCall' => $method,
+                ];
+            }
+        }
+        return $scenarios;
+    }
+
+    /**
+     * @dataProvider provideLazyLoadedDoesntCallGetSource
+     */
+    public function testLazyLoadedDoesntCallGetSource(string $fieldClass, string $methodToCall)
+    {
+        // Some methods aren't shared between the two form fields.
+        if (!ClassInfo::hasMethod($fieldClass, $methodToCall)) {
+            $this->markTestSkipped("$fieldClass doesn't have method $methodToCall - skipping");
+        }
+        // We have to disable the constructor because it ends up calling a static method, and we can't call static methods on mocks.
+        $mockField = $this->getMockBuilder($fieldClass)->onlyMethods(['getSource'])->disableOriginalConstructor()->getMock();
+        $mockField->expects($this->never())->method('getSource');
+        $mockField->setIsLazyLoaded(true);
+        $mockField->setSource(Team::get());
+        $mockField->setForm(new Form());
+        $mockField->$methodToCall();
+    }
 }