Prometheus: Add backslash escaping for template variables (#26205)

* Run query on splitOpen action

* Escape \ in prometheusRegularEscape

* Revert "Run query on splitOpen action"

This reverts commit 3559b6c5739f351f4e797c57069bc937bd06c065.

Co-authored-by: Andrej Ocenas <mr.ocenas@gmail.com>

public/app/plugins/datasource/prometheus/datasource.test.ts

@@ -415,9 +415,17 @@ describe('PrometheusDatasource', () => {
       expect(prometheusRegularEscape("looking'glass")).toEqual("looking\\\\'glass");
     });
 
+    it('should escape \\', () => {
+      expect(prometheusRegularEscape('looking\\glass')).toEqual('looking\\\\glass');
+    });
+
     it('should escape multiple characters', () => {
       expect(prometheusRegularEscape("'looking'glass'")).toEqual("\\\\'looking\\\\'glass\\\\'");
     });
+
+    it('should escape multiple different characters', () => {
+      expect(prometheusRegularEscape("'loo\\king'glass'")).toEqual("\\\\'loo\\\\king\\\\'glass\\\\'");
+    });
   });
 
   describe('Prometheus regexes escaping', () => {

public/app/plugins/datasource/prometheus/datasource.ts

@@ -764,11 +764,9 @@ export function extractRuleMappingFromGroups(groups: any[]) {
 }
 
 export function prometheusRegularEscape(value: any) {
-  return typeof value === 'string' ? value.replace(/'/g, "\\\\'") : value;
+  return typeof value === 'string' ? value.replace(/\\/g, '\\\\').replace(/'/g, "\\\\'") : value;
 }
 
 export function prometheusSpecialRegexEscape(value: any) {
-  return typeof value === 'string'
-    ? prometheusRegularEscape(value.replace(/\\/g, '\\\\\\\\').replace(/[$^*{}\[\]+?.()|]/g, '\\\\$&'))
-    : value;
+  return typeof value === 'string' ? value.replace(/\\/g, '\\\\\\\\').replace(/[$^*{}\[\]\'+?.()|]/g, '\\\\$&') : value;
 }