Issue #3096969 by quietone, gabesullice, Wim Leers, mikelutz: migrate_drupal's...

Issue #3096969 by quietone, gabesullice, Wim Leers, mikelutz: migrate_drupal's Variable source plugin always returns a row for processing, even if none of the variables for a migration are set on the source site

core/modules/migrate_drupal/src/Plugin/migrate/source/Variable.php

@@ -60,7 +60,8 @@ protected function values() {
    * {@inheritdoc}
    */
   public function count($refresh = FALSE) {
-    return intval($this->query()->countQuery()->execute()->fetchField() > 0);
+    // Variable always returns a single row with at minimum an 'id' property.
+    return 1;
   }
 
   /**

core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/VariableTest.php

@@ -48,6 +48,42 @@ public function providerSource() {
       'bar',
     ];
 
+    // Tests getting one of two variables.
+    $tests[1]['source_data']['variable'] = [
+      ['name' => 'foo', 'value' => 'i:1;'],
+      ['name' => 'bar', 'value' => 'b:0;'],
+    ];
+
+    $tests[1]['expected_data'] = [
+      [
+        'id' => 'foo',
+        'foo' => 1,
+      ],
+    ];
+
+    $tests[1]['expected_count'] = NULL;
+
+    $tests[1]['configuration']['variables'] = [
+      'foo',
+      'bar0',
+    ];
+
+    // Tests requesting mis-spelled variable names.
+    $tests[2]['source_data']['variable'] = [
+      ['name' => 'foo', 'value' => 'i:1;'],
+      ['name' => 'bar', 'value' => 'b:0;'],
+    ];
+    $tests[2]['expected_data'] = [
+      [
+        'id' => 'foo0',
+      ],
+    ];
+    $tests[2]['expected_count'] = NULL;
+    $tests[2]['configuration']['variables'] = [
+      'foo0',
+      'bar0',
+    ];
+
     return $tests;
   }