API Only include gridfield state value that differ from the expected default

src/Forms/GridField/GridField.php

@@ -156,8 +156,6 @@ class GridField extends FormField
 
         $this->setConfig($config);
 
-        $this->state = new GridState($this);
-
         $this->addExtraClass('grid-field');
     }
 
@@ -407,6 +405,11 @@ class GridField extends FormField
      */
     public function getState($getData = true)
     {
+        // Initialise state on first call. This ensures it's evaluated after components have been added
+        if (!$this->state) {
+            $this->initState();
+        }
+
         if ($getData) {
             return $this->state->getData();
         }
@@ -414,6 +417,19 @@ class GridField extends FormField
         return $this->state;
     }
 
+    private function initState(): void
+    {
+        $this->state = new GridState($this);
+
+        $data = $this->state->getData();
+
+        foreach ($this->getComponents() as $item) {
+            if ($item instanceof GridField_StateProvider) {
+                $item->initDefaultState($data);
+            }
+        }
+    }
+
     /**
      * Returns the whole gridfield rendered with all the attached components.
      *

src/Forms/GridField/GridFieldFilterHeader.php

@@ -26,7 +26,7 @@ use SilverStripe\View\SSViewer;
  *
  * @see GridField
  */
-class GridFieldFilterHeader implements GridField_URLHandler, GridField_HTMLProvider, GridField_DataManipulator, GridField_ActionProvider
+class GridFieldFilterHeader implements GridField_URLHandler, GridField_HTMLProvider, GridField_DataManipulator, GridField_ActionProvider, GridField_StateProvider
 {
     /**
      * See {@link setThrowExceptionOnBadDataType()}
@@ -173,8 +173,8 @@ class GridFieldFilterHeader implements GridField_URLHandler, GridField_HTMLProvi
             return;
         }
 
-        $state = $gridField->State->GridFieldFilterHeader;
-        $state->Columns = null;
+        $state = $this->getState($gridField);
+
         if ($actionName === 'filter') {
             if (isset($data['filter'][$gridField->getName()])) {
                 foreach ($data['filter'][$gridField->getName()] as $key => $filter) {
@@ -184,6 +184,20 @@ class GridFieldFilterHeader implements GridField_URLHandler, GridField_HTMLProvi
         }
     }
 
+    /**
+     * Extract state data from the parent gridfield
+     * @param GridField $gridField
+     * @return GridState_Data
+     */
+    private function getState(GridField $gridField): GridState_Data
+    {
+        return $gridField->State->GridFieldFilterHeader;
+    }
+
+    public function initDefaultState(GridState_Data $data): void
+    {
+        $data->GridFieldFilterHeader->initDefaults(['Columns' => []]);
+    }
 
     /**
      * @inheritDoc
@@ -195,13 +209,12 @@ class GridFieldFilterHeader implements GridField_URLHandler, GridField_HTMLProvi
         }
 
         /** @var Filterable $dataList */
-        /** @var GridState_Data $columns */
-        $columns = $gridField->State->GridFieldFilterHeader->Columns(null);
-        if (empty($columns)) {
+        /** @var array $filterArguments */
+        $filterArguments = $this->getState($gridField)->Columns->toArray();
+        if (empty($filterArguments)) {
             return $dataList;
         }
 
-        $filterArguments = $columns->toArray();
         $dataListClone = clone($dataList);
         $results = $this->getSearchContext($gridField)
             ->getQuery($filterArguments, false, false, $dataListClone);
@@ -413,7 +426,7 @@ class GridFieldFilterHeader implements GridField_URLHandler, GridField_HTMLProvi
         }
 
         $columns = $gridField->getColumns();
-        $filterArguments = $gridField->State->GridFieldFilterHeader->Columns->toArray();
+        $filterArguments = $this->getState($gridField)->Columns->toArray();
         $currentColumn = 0;
         $canFilter = false;
         $fieldsList = new ArrayList();

src/Forms/GridField/GridFieldPaginator.php

@@ -14,7 +14,7 @@ use LogicException;
  * GridFieldPaginator paginates the {@link GridField} list and adds controls
  * to the bottom of the {@link GridField}.
  */
-class GridFieldPaginator implements GridField_HTMLProvider, GridField_DataManipulator, GridField_ActionProvider
+class GridFieldPaginator implements GridField_HTMLProvider, GridField_DataManipulator, GridField_ActionProvider, GridField_StateProvider
 {
     use Configurable;
 
@@ -140,13 +140,15 @@ class GridFieldPaginator implements GridField_HTMLProvider, GridField_DataManipu
      */
     protected function getGridPagerState(GridField $gridField)
     {
-        $state = $gridField->State->GridFieldPaginator;
+        return $gridField->State->GridFieldPaginator;
+    }
 
-        // Force the state to the initial page if none is set
-        $state->currentPage(1);
-        $state->itemsPerPage($this->getItemsPerPage());
-
-        return $state;
+    public function initDefaultState(GridState_Data $data): void
+    {
+        $data->GridFieldPaginator->initDefaults([
+            'currentPage' => 1,
+            'itemsPerPage' => $this->getItemsPerPage()
+        ]);
     }
 
     /**

src/Forms/GridField/GridFieldSortableHeader.php

@@ -18,7 +18,7 @@ use LogicException;
  *
  * @see GridField
  */
-class GridFieldSortableHeader implements GridField_HTMLProvider, GridField_DataManipulator, GridField_ActionProvider
+class GridFieldSortableHeader implements GridField_HTMLProvider, GridField_DataManipulator, GridField_ActionProvider, GridField_StateProvider
 {
 
     /**
@@ -119,7 +119,7 @@ class GridFieldSortableHeader implements GridField_HTMLProvider, GridField_DataM
         $forTemplate = new ArrayData([]);
         $forTemplate->Fields = new ArrayList;
 
-        $state = $gridField->State->GridFieldSortableHeader;
+        $state = $this->getState($gridField);
         $columns = $gridField->getColumns();
         $currentColumn = 0;
 
@@ -236,7 +236,7 @@ class GridFieldSortableHeader implements GridField_HTMLProvider, GridField_DataM
             return;
         }
 
-        $state = $gridField->State->GridFieldSortableHeader;
+        $state = $this->getState($gridField);
         switch ($actionName) {
             case 'sortasc':
                 $state->SortColumn = $arguments['SortColumn'];
@@ -266,11 +266,26 @@ class GridFieldSortableHeader implements GridField_HTMLProvider, GridField_DataM
         }
 
         /** @var Sortable $dataList */
-        $state = $gridField->State->GridFieldSortableHeader;
+        $state = $this->getState($gridField);
         if ($state->SortColumn == "") {
             return $dataList;
         }
 
         return $dataList->sort($state->SortColumn, $state->SortDirection('asc'));
     }
+
+    /**
+     * Extract state data from the parent gridfield
+     * @param GridField $gridField
+     * @return GridState_Data
+     */
+    private function getState(GridField $gridField): GridState_Data
+    {
+        return $gridField->State->GridFieldSortableHeader;
+    }
+
+    public function initDefaultState(GridState_Data $data): void
+    {
+        $data->GridFieldSortableHeader->initDefaults(['SortColumn' => null, 'SortDirection' => 'asc']);
+    }
 }

src/Forms/GridField/GridFieldStateManager.php

@@ -41,6 +41,11 @@ class GridFieldStateManager implements GridFieldStateManagerInterface
         $key = $this->getStateKey($gridField);
         $value = $gridField->getState(false)->Value();
 
+        // Using a JSON-encoded empty array as the blank value, to avoid changing Value() semantics in a minor release
+        if ($value === '[]') {
+            return $url;
+        }
+
         return HTTP::setGetVar($key, $value, $url);
     }
 

src/Forms/GridField/GridField_StateProvider.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace SilverStripe\Forms\GridField;
+
+/**
+ * A GridField component that provides state, notably default state.
+ *
+ * Implementation of this interface is optional; without it, no default state is assumed.
+ * The benefit of default state is that it won't be included in URLs, keeping URLs tidier.
+ */
+interface GridField_StateProvider extends GridFieldComponent
+{
+    /**
+     * Initialise the default state in the given GridState_Data
+     *
+     * We recommend that you call $data->initDefaults() to do this.
+     *
+     * @param $data The top-level sate object
+     */
+    public function initDefaultState(GridState_Data $data): void;
+}

src/Forms/GridField/GridState.php

@@ -59,14 +59,26 @@ class GridState extends HiddenField
 
     public function setValue($value, $data = null)
     {
-        if (is_string($value)) {
-            $this->data = new GridState_Data(json_decode($value, true));
+        // Apply the value on top of the existing defaults
+        $data = json_decode($value, true);
+        if ($data) {
+            $this->mergeValues($this->getData(), $data);
         }
-
         parent::setValue($value);
         return $this;
     }
 
+    private function mergeValues(GridState_Data $data, array $array): void
+    {
+        foreach ($array as $k => $v) {
+            if (is_array($v)) {
+                $this->mergeValues($data->$k, $v);
+            } else {
+                $data->$k = $v;
+            }
+        }
+    }
+
     /**
      * @return GridState_Data
      */
@@ -98,7 +110,7 @@ class GridState extends HiddenField
             return json_encode([]);
         }
 
-        return json_encode($this->data->toArray());
+        return json_encode($this->data->getChangesArray());
     }
 
     /**

src/Forms/GridField/GridState_Data.php

@@ -16,6 +16,8 @@ class GridState_Data
      */
     protected $data;
 
+    protected $defaults = [];
+
     public function __construct($data = [])
     {
         $this->data = $data;
@@ -23,30 +25,49 @@ class GridState_Data
 
     public function __get($name)
     {
-        return $this->getData($name, new GridState_Data());
+        return $this->getData($name, new self());
     }
 
     public function __call($name, $arguments)
     {
         // Assume first parameter is default value
-        $default = empty($arguments) ? new GridState_Data() : $arguments[0];
+        if (empty($arguments)) {
+            $default = new self();
+        } else {
+            $default = $arguments[0];
+        }
+
         return $this->getData($name, $default);
     }
 
+    /**
+     * Initialise the defaults values for the grid field state
+     * These values won't be included in getChangesArray()
+     *
+     * @param array $defaults
+     */
+    public function initDefaults(array $defaults): void
+    {
+        foreach ($defaults as $key => $value) {
+            $this->defaults[$key] = $value;
+            $this->getData($key, $value);
+        }
+    }
+
     /**
      * Retrieve the value for the given key
      *
      * @param string $name The name of the value to retrieve
-     * @param mixed $default Default value to assign if not set
+     * @param mixed $default Default value to assign if not set. Note that this *will* be included in getChangesArray()
      * @return mixed The value associated with this key, or the value specified by $default if not set
      */
     public function getData($name, $default = null)
     {
-        if (!isset($this->data[$name])) {
+        if (!array_key_exists($name, $this->data)) {
             $this->data[$name] = $default;
         } else {
             if (is_array($this->data[$name])) {
-                $this->data[$name] = new GridState_Data($this->data[$name]);
+                $this->data[$name] = new self($this->data[$name]);
             }
         }
 
@@ -77,6 +98,9 @@ class GridState_Data
         return json_encode($this->toArray());
     }
 
+    /**
+     * Return all data, including defaults, as array
+     */
     public function toArray()
     {
         $output = [];
@@ -85,6 +109,34 @@ class GridState_Data
             $output[$k] = (is_object($v) && method_exists($v, 'toArray')) ? $v->toArray() : $v;
         }
 
+        return $output;
+    }
+    /**
+     * Convert the state to an array including only value that differ from the default state defined by initDefaults()
+     * @return array
+     */
+    public function getChangesArray(): array
+    {
+        $output = [];
+
+        foreach ($this->data as $k => $v) {
+            if (is_object($v) && method_exists($v, 'getChangesArray')) {
+                $value = $v->getChangesArray();
+                // Empty arrays represent pristine data, so we do not include them
+                if (empty($value)) {
+                    continue;
+                }
+            } else {
+                $value = $v;
+                // Check if we have a default value for this key and if it matches our current value
+                if (array_key_exists($k, $this->defaults) && $this->defaults[$k] === $value) {
+                    continue;
+                }
+            }
+
+            $output[$k] = $value;
+        }
+
         return $output;
     }
 }

tests/php/Forms/GridField/GridFieldStateManagerTest.php

@@ -79,4 +79,19 @@ class GridFieldStateManagerTest extends SapphireTest
 
         $this->assertEquals($state, $result);
     }
+
+    public function testDefaultStateLeavesURLUnchanged()
+    {
+        $manager = new GridFieldStateManager();
+        $grid = new GridField('TestGrid');
+        $grid->getState()->initDefaults(['testValue' => 'foo']);
+        $link = '/link-to/something';
+
+        $this->assertEquals('[]', $grid->getState(false)->Value());
+
+        $this->assertEquals(
+            '/link-to/something',
+            $manager->addStateToURL($grid, $link)
+        );
+    }
 }

tests/php/Forms/GridField/GridStateDataTest.php

@@ -0,0 +1,83 @@
+<?php
+
+namespace SilverStripe\Forms\Tests\GridField;
+
+use SilverStripe\Forms\GridField\GridState_Data;
+use SilverStripe\Forms\GridField\GridState;
+use SilverStripe\Forms\GridField\GridField;
+use SilverStripe\Dev\SapphireTest;
+
+class GridStateDataTest extends SapphireTest
+{
+
+    public function testGetData()
+    {
+        $state = new GridState_Data();
+
+        $this->assertEquals('Bar', $state->getData('Foo', 'Bar'));
+        $this->assertEquals('Bar', $state->Foo);
+        $this->assertEquals('Bar', $state->getData('Foo', 'Hello World'));
+    }
+
+    public function testCall()
+    {
+        $state = new GridState_Data();
+
+        $foo = $state->Foo();
+        $this->assertInstanceOf(GridState_Data::class, $foo);
+
+        $bar = $state->Bar(123456);
+        $this->assertEquals(123456, $bar);
+
+        $zone = $state->Zone(null);
+        $this->assertEquals(null, $zone);
+    }
+
+    public function testInitDefaults()
+    {
+        $state = new GridState_Data();
+        $state->initDefaults(['Foo' => 'Bar', 'Hello' => 'World']);
+
+        $this->assertEquals('Bar', $state->Foo);
+        $this->assertEquals('World', $state->Hello);
+    }
+
+    public function testToArray()
+    {
+        $state = new GridState_Data();
+
+        $this->assertEquals([], $state->toArray());
+
+        $state->Foo = 'Bar';
+        $this->assertEquals(['Foo' => 'Bar'], $state->toArray());
+
+        $state->initDefaults(['Foo' => 'Bar', 'Hello' => 'World']);
+
+        $this->assertEquals(['Foo' => 'Bar', 'Hello' => 'World'], $state->toArray());
+        $this->assertEquals([], $state->getChangesArray());
+
+        $boom = $state->Boom();
+        $boom->Pow = 'Kaboom';
+
+        $state->Boom(null);
+
+        $this->assertEquals(['Foo' => 'Bar', 'Hello' => 'World', 'Boom' => ['Pow' => 'Kaboom']], $state->toArray());
+        $this->assertEquals(['Boom' => ['Pow' => 'Kaboom']], $state->getChangesArray());
+    }
+
+    public function testInitDefaultsAfterSetValue()
+    {
+        $state = new GridState(new GridField('x'));
+        $state->setValue('{"Foo":{"Bar":"Baz","Wee":null}}');
+        $data = $state->getData();
+
+        $data->Foo->initDefaults([
+            'Bar' => 'Bing',
+            'Zoop' => 'Zog',
+            'Wee' => 'Wing',
+        ]);
+
+        $this->assertEquals(['Bar' => 'Baz', 'Zoop' => 'Zog', 'Wee' => null], $data->Foo->toArray());
+        $this->assertEquals(['Bar' => 'Baz', 'Wee' => null], $data->Foo->getChangesArray());
+    }
+}