Issue #1588138 by mondrake: pager_query_add_page() overrides parameters passed programmatically

core/includes/pager.inc

@@ -304,8 +304,11 @@ function pager_query_add_page(array $query, $element, $index) {
   if ($new_page = implode(',', pager_load_array($page_new[$element], $element, explode(',', $page)))) {
     $query['page'] = $new_page;
   }
-  if ($query_pager = pager_get_query_parameters()) {
-    $query = array_merge($query, $query_pager);
+  // Merge the query parameters passed to this function with the parameters
+  // from the current request. In case of collision, the parameters passed
+  // into this function take precedence.
+  if ($current_request_query = pager_get_query_parameters()) {
+    $query = array_merge($current_request_query, $query);
   }
   return $query;
 }

core/modules/system/src/Tests/Pager/PagerTest.php

@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\system\Tests\Pager\PagerTest.
+ * Contains \Drupal\system\Tests\Pager\PagerTest.
  */
 
 namespace Drupal\system\Tests\Pager;
@@ -21,7 +21,7 @@ class PagerTest extends WebTestBase {
    *
    * @var array
    */
-  public static $modules = array('dblog');
+  public static $modules = array('dblog', 'pager_test');
 
   protected $profile = 'testing';
 
@@ -62,6 +62,25 @@ function testActiveClass() {
     $this->assertPagerItems($current_page);
   }
 
+  /**
+   * Test proper functioning of the query parameters.
+   */
+  protected function testPagerQueryParameters() {
+    // First page.
+    $this->drupalGet('pager-test/query-parameters');
+    $this->assertText(t('Pager calls: 0'), 'Initial call to pager shows 0 calls.');
+
+    // Go to last page, the count of pager calls need to go to 1.
+    $elements = $this->xpath('//li[contains(@class, :class)]/a', array(':class' => 'pager__item--last'));
+    $this->drupalGet($GLOBALS['base_root'] . $elements[0]['href'], array('external' => TRUE));
+    $this->assertText(t('Pager calls: 1'), 'First link call to pager shows 1 calls.');
+
+    // Go back to first page, the count of pager calls need to go to 2.
+    $elements = $this->xpath('//li[contains(@class, :class)]/a', array(':class' => 'pager__item--first'));
+    $this->drupalGet($GLOBALS['base_root'] . $elements[0]['href'], array('external' => TRUE));
+    $this->assertText(t('Pager calls: 2'), 'Second link call to pager shows 2 calls.');
+  }
+
   /**
    * Asserts pager items and links.
    *

core/modules/system/tests/modules/pager_test/pager_test.info.yml

+type: module
+core: 8.x
+name: 'Pager Test'
+description: 'Support module for pager tests.'
+package: Testing
+version: VERSION

core/modules/system/tests/modules/pager_test/pager_test.routing.yml

+pager_test.query_parameters:
+  path: '/pager-test/query-parameters'
+  defaults:
+    _title: 'Pager using query parameters for testing'
+    _controller: '\Drupal\pager_test\Controller\PagerTestController::queryParameters'
+  requirements:
+    _access: 'TRUE'

core/modules/system/tests/modules/pager_test/src/Controller/PagerTestController.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\pager_test\Controller\PagerTestController.
+ */
+
+namespace Drupal\pager_test\Controller;
+
+use Drupal\Core\Controller\ControllerBase;
+
+/**
+ * Controller routine for testing the pager.
+ */
+class PagerTestController extends ControllerBase {
+
+  /**
+   * Returns a pager with 'parameters' variable.
+   *
+   * The 'pager_calls' parameter counts the calls to the pager, subsequent
+   * to the initial call.
+   */
+  public function queryParameters() {
+
+    // Example query.
+    $header_0 = array(
+      array('data' => 'wid'),
+      array('data' => 'type'),
+      array('data' => 'timestamp'),
+    );
+    $query_0 = db_select('watchdog', 'd')->extend('Drupal\Core\Database\Query\PagerSelectExtender')->element(0);
+    $query_0->fields('d', array('wid', 'type', 'timestamp'));
+    $result_0 = $query_0
+      ->limit(5)
+      ->orderBy('d.wid')
+      ->execute();
+    $rows_0 = array();
+    foreach ($result_0 as $row) {
+      $rows_0[] = array('data' => (array) $row);
+    }
+    $build['pager_table_0'] = array(
+      '#theme' => 'table',
+      '#header' => $header_0,
+      '#rows' => $rows_0,
+      '#empty' => $this->t("There are no watchdog records found in the db"),
+    );
+
+    // Counter of calls to the current pager.
+    $query_params = pager_get_query_parameters();
+    $pager_calls = isset($query_params['pager_calls']) ? ($query_params['pager_calls'] ? $query_params['pager_calls'] : 0) : 0;
+    $build['l_pager_pager_0'] = array('#markup' => $this->t('Pager calls: @pager_calls', array('@pager_calls' => $pager_calls)));
+
+    // Pager.
+    $build['pager_pager_0'] = array(
+      '#theme' => 'pager',
+      '#element' => 0,
+      '#parameters' => array(
+        'pager_calls' => ++$pager_calls,
+      ),
+    );
+
+    return $build;
+  }
+}