Issue #1903176 by tim.plunkett: Add a drupal_build_form() helper for using a method as the callback.

core/includes/form.inc

@@ -137,6 +137,28 @@ function drupal_get_form($form_id) {
   return drupal_build_form($form_id, $form_state);
 }
 
+/**
+ * Returns a renderable form array using a specific callback.
+ *
+ * When using drupal_get_form(), the $form_id or information from hook_forms()
+ * is used to determine the callback used to build the form. If the callback
+ * needs to be explicitly specified, or if it is a method, use this function.
+ *
+ * @param string $form_id
+ *   The unique string identifying the desired form.
+ * @param callable $callback
+ *   A callback to be used for building the form.
+ * @param array $args
+ *   (optional) An array of arguments to pass to the form callback. Defaults to
+ *   an empty array.
+ */
+function drupal_get_callback_form($form_id, $callback, array $args = array()) {
+  $form_state = array();
+  $form_state['build_info']['args'] = $args;
+  $form_state['build_info']['callback'] = $callback;
+  return drupal_build_form($form_id, $form_state);
+}
+
 /**
  * Builds and processes a form for a given form ID.
  *

core/modules/block/lib/Drupal/block/BlockListController.php

@@ -55,10 +55,7 @@ class BlockListController extends ConfigEntityListController {
     // If no theme was specified, use the current theme.
     $this->theme = $theme ?: $GLOBALS['theme_key'];
 
-    $form_state = array();
+    return drupal_get_callback_form('block_admin_display_form', array($this, 'form'));
-    $form_state['build_info']['args'] = array();
-    $form_state['build_info']['callback'] = array($this, 'form');
-    return drupal_build_form('block_admin_display_form', $form_state);
   }
 
   /**

core/modules/field_ui/field_ui.admin.inc

@@ -315,11 +315,7 @@ function field_ui_field_overview($entity_type, $bundle) {
 
   $field_overview = new FieldOverview($entity_type, $bundle);
 
-  $form_state = array();
+  return drupal_get_callback_form('field_ui_field_overview_form', array($field_overview, 'form'), array($entity_type, $bundle));
-  $form_state['build_info']['callback'] = array($field_overview, 'form');
-  $form_state['build_info']['args'] = array($entity_type, $bundle);
-
-  return drupal_build_form('field_ui_field_overview_form', $form_state);
 }
 
 /**
@@ -366,11 +362,7 @@ function field_ui_display_overview($entity_type, $bundle, $view_mode) {
 
   $display_overview = new DisplayOverview($entity_type, $bundle, $view_mode);
 
-  $form_state = array();
+  return drupal_get_callback_form('field_ui_display_overview_form', array($display_overview, 'form'), array($entity_type, $bundle, $view_mode));
-  $form_state['build_info']['callback'] = array($display_overview, 'form');
-  $form_state['build_info']['args'] = array($entity_type, $bundle, $view_mode);
-
-  return drupal_build_form('field_ui_display_overview_form', $form_state);
 }
 
 /**

core/modules/system/lib/Drupal/system/Tests/Form/CallbackBuilderTest.php

@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Form\CallbackBuilderTest.
+ */
+
+namespace Drupal\system\Tests\Form;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests form builder callbacks.
+ */
+class CallbackBuilderTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('form_test');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Form builder callbacks',
+      'description' => 'Tests form builder callbacks.',
+      'group' => 'Form API',
+    );
+  }
+
+  /**
+   * Tests using a static method to build a form.
+   */
+  function testStaticMethodCallback() {
+    $this->drupalGet('form-test/callback-builder');
+    $this->assertText('The Callbacks::buildForm() method was used for this form.');
+    $elements = $this->xpath('//form[@id="form-test-callback-builder-form"]');
+    $this->assertTrue(!empty($elements), 'The correct form ID was used even when it is not the callback function name.');
+  }
+
+}

core/modules/system/tests/modules/form_test/form_test.module

@@ -25,6 +25,13 @@ function form_test_menu() {
     'access callback' => TRUE,
     'type' => MENU_CALLBACK,
   );
+  $items['form-test/callback-builder'] = array(
+    'title' => 'Form callback builder test',
+    'page callback' => 'drupal_get_callback_form',
+    'page arguments' => array('form_test_callback_builder_form', '\Drupal\form_test\Callbacks::buildForm'),
+    'access callback' => TRUE,
+    'type' => MENU_CALLBACK,
+  );
   $items['form-test/validate-required'] = array(
     'title' => 'Form #required validation',
     'page callback' => 'drupal_get_form',

core/modules/system/tests/modules/form_test/lib/Drupal/form_test/Callbacks.php

@@ -8,7 +8,7 @@
 namespace Drupal\form_test;
 
 /**
- * Simple class for testing methods as element validation callbacks.
+ * Simple class for testing methods as Form API callbacks.
  */
 class Callbacks {
 
@@ -47,4 +47,13 @@ class Callbacks {
       form_set_error('');
     }
   }
+
+  /**
+   * Form constructor for the Form callback builder test form.
+   */
+  public static function buildForm($form, &$form_state) {
+    $form['element'] = array('#markup' => 'The Callbacks::buildForm() method was used for this form.');
+    return $form;
+  }
+
 }