Highlight in red host names in rule conditions that no longer exist

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to **Checkmk SwissKnife** are documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.24.0] - 2026-09-28
+
+### Added
+- On rule list pages (`mode=edit_ruleset`), exact host names in a rule's "Host name" condition that are not linked to a host (i.e. the host no longer exists in Checkmk) are now highlighted in red with a tooltip. Regexes, host groups and host tags are ignored, and the highlight works for mixed conditions ("matches regex …, is host01 or matches regex …") and for negated ones ("is not" / "does not match regex").
+
 ## [2.23.0] - 2026-09-28
 
 ### Added

README.md

@@ -24,6 +24,7 @@ A [Tampermonkey](https://www.tampermonkey.net/) userscript that enhances the Che
 | **Rule Match Status** | Colors each rule row green (match) or dimmed (no match) when a ruleset is opened with host/service context | `highlightRuleMatchStatus` |
 | **Relevant Only Filter** | Adds a "Relevant only" toggle above the rule list to hide all non-matching and non-highlighted rows | `addRulesetFilterToggle` |
 | **Ruleset Free-Text Filter** | Adds a search box above the rule list on any ruleset page to hide rules and folders whose row text doesn't contain the typed string; mutually exclusive with "Relevant only" | `addRulesetTextFilter` |
+| **Missing Host Highlight** | Paints in red the exact host names in a rule's "Host name" condition that are not linked to a host, i.e. hosts that no longer exist | `highlightMissingHosts` |
 | **Extra Column — Host Actions** | Inserts an Extra column in monitoring tables with per-host buttons: Service Discovery, copy FQDN, copy short hostname, copy IP | `addInventoryButtons` |
 | **Monitor Button in WATO Folder** | Adds a green eye icon next to each active host in WATO folder listings to open its monitoring view in a new tab | `addWatoFolderMonitorButtons` |
 | **Configure in WATO Menu** | Adds a host-selector dropdown and Open button to the monitoring view menu bar for bulk-opening hosts in WATO | `addViewWatoMenu` |
@@ -90,6 +91,13 @@ Applies to: every `mode=edit_ruleset` page, with or without host/service context
 
 ---
 
+### Missing Host Highlight
+In a rule's "Host name" condition, exact host names that are not linked to a host (the host no longer exists in Checkmk) are shown in red with a wavy underline and a tooltip. Regexes, host groups and host tags are ignored. Works on mixed conditions ("matches regex …, is host01 or matches regex …") and on negated ones ("is not", "does not match regex").
+
+Applies to: every `mode=edit_ruleset` page, with or without host/service context.
+
+---
+
 ### Extra Column with Host Actions
 Adds a dedicated **Extra** column before the Host column in all monitoring view tables. Each row gets up to four icon buttons:
 

user_script/checkmk_swissknife.user.js

@@ -1,7 +1,7 @@
 // ==UserScript==
 // @name         Checkmk SwissKnife
 // @namespace    https://luigidacunto.com/
-// @version      2.23.0
+// @version      2.24.0
 // @checkmk      2.3.x - 2.4.x
 // @description  Collection of UI improvements for Checkmk WATO. Each fix or enhancement is added here as an independent feature.
 // @author       Luigi D'Acunto
@@ -893,6 +893,37 @@
   }
 
 
+  // =========================================================================
+  // FEATURE: Missing Host Highlight
+  //
+  // In a rule's "Host name ..." condition, exact host names are rendered as a
+  // link to the host only if the host still exists; an unlinked name means the
+  // host was deleted. Those names are painted red. Regexes are ignored.
+  // =========================================================================
+
+  function highlightMissingHosts(doc) {
+    if (doc.body.dataset.cmkMissingHosts === '1') return;
+    const items = doc.querySelectorAll('tr.data li.condition');
+    if (!items.length) return;
+    doc.body.dataset.cmkMissingHosts = '1';
+
+    injectStyles(doc, 'cmk-sk-missing-host-styles', `
+      b.cmk-sk-missing-host { color: #ff4d4d !important; text-decoration: underline wavy #ff4d4d; }
+    `);
+
+    items.forEach(li => {
+      if (!li.textContent.trim().startsWith('Host name')) return;
+      li.querySelectorAll('b').forEach(b => {
+        // Text right before each <b> tells regex ("matches regex", "one of regex") from exact name ("is", "is not")
+        const before = b.previousSibling ? b.previousSibling.textContent : '';
+        if (/regex/.test(before) || b.querySelector('a')) return;
+        b.classList.add('cmk-sk-missing-host');
+        b.title = 'Host not found in Checkmk (deleted?)';
+      });
+    });
+  }
+
+
   // =========================================================================
   // FEATURE: Inventory Button on view.py
   //
@@ -2049,6 +2080,7 @@
     highlightRuleMatchStatus(doc);
     addRulesetFilterToggle(doc);
     addRulesetTextFilter(doc);
+    highlightMissingHosts(doc);
   }
 
   function tryAddInventoryButtons() {