Issue #2650910 by drpal, Anishnirmal, markdorison, Tom Robert, psend, yannickoo, rachel_norfolk, Wim Leers, droplet: Contextual links button is always rendered even when no links are available (with warm client-side cache)

core/modules/contextual/js/contextual.js

@@ -163,7 +163,7 @@
       // Update all contextual links placeholders whose HTML is cached.
       var uncachedIDs = _.filter(ids, function initIfCached(contextualID) {
         var html = storage.getItem('Drupal.contextual.' + contextualID);
-        if (html !== null) {
+        if (html && html.length) {
           // Initialize after the current execution cycle, to make the AJAX
           // request for retrieving the uncached contextual links as soon as
           // possible, but also to ensure that other Drupal behaviors have had

core/modules/contextual/tests/src/FunctionalJavascript/ContextualLinksTest.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace Drupal\Tests\contextual\FunctionalJavascript;
+
+use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
+use Drupal\user\Entity\Role;
+
+/**
+ * Tests the UI for correct contextual links.
+ *
+ * @group contextual
+ */
+class ContextualLinksTest extends JavascriptTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['block', 'contextual'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->placeBlock('system_branding_block', ['id' => 'branding']);
+  }
+
+  /**
+   * Tests the visibility of contextual links.
+   */
+  public function testContextualLinksVisibility() {
+    $this->drupalLogin($this->drupalCreateUser([
+      'access contextual links'
+    ]));
+
+    $this->drupalGet('user');
+    $contextualLinks = $this->assertSession()->waitForElement('css', '.contextual button');
+    $this->assertEmpty($contextualLinks);
+
+    // Ensure visibility remains correct after cached paged load.
+    $this->drupalGet('user');
+    $contextualLinks = $this->assertSession()->waitForElement('css', '.contextual button');
+    $this->assertEmpty($contextualLinks);
+
+    // Grant permissions to use contextual links on blocks.
+    $this->grantPermissions(Role::load(Role::AUTHENTICATED_ID), [
+      'access contextual links',
+      'administer blocks',
+    ]);
+
+    $this->drupalGet('user');
+    $contextualLinks = $this->assertSession()->waitForElement('css', '.contextual button');
+    $this->assertNotEmpty($contextualLinks);
+
+    // Ensure visibility remains correct after cached paged load.
+    $this->drupalGet('user');
+    $contextualLinks = $this->assertSession()->waitForElement('css', '.contextual button');
+    $this->assertNotEmpty($contextualLinks);
+  }
+
+}