Ticket #31002: 31002.2.diff

src/wp-admin/includes/class-wp-plugin-install-list-table.php

@@ -467 +467 @@
                                                 break;
                                         case 'latest_installed':
                                         case 'newer_installed':
-                                                $action_links[] = '<span class="button button-disabled">' . _x( 'Installed', 'plugin' ) . '</span>';
+                                                $plugins = get_plugins( '/' . $plugin['slug'] );
+                                                $plugin_file = '';
+
+                                                if ( ! empty( $plugins ) ) {
+                                                        $plugin_file = $plugin['slug'] . '/' . key( $plugins );
+                                                }
+
+                                                if ( $plugin_file && ! is_plugin_active( $plugin_file ) ) {
+
+                                                        $activate_url = wp_nonce_url( 'plugins.php?action=activate&amp;plugin=' . $plugin_file, 'activate-plugin_' . $plugin_file );
+                                                        $action_links[] = sprintf( '<a class="button" href="%s" title="%s" target="_parent">%s</a>', esc_url( $activate_url ), esc_attr__( 'Activate this plugin' ), _x( 'Activate', 'plugin' ) );
+                                                } else {
+                                                        $action_links[] = sprintf( '<span class="button button-disabled" title="%s">%s</span>', esc_attr__( 'This plugin is already installed and is up to date' ), _x( 'Installed', 'plugin' ) );
+                                                }
                                                 break;
                                 }
                         }