Prometheus: Correctly format multi values variables in queries (#26896)

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

@@ -500,7 +500,7 @@ describe('PrometheusDatasource', () => {
       });
 
       it('should return pipe separated values if the value is an array of strings', () => {
-        expect(ds.interpolateQueryExpr(['a|bc', 'de|f'], customVariable)).toEqual('a\\\\|bc|de\\\\|f');
+        expect(ds.interpolateQueryExpr(['a|bc', 'de|f'], customVariable)).toEqual('(a\\\\|bc|de\\\\|f)');
       });
     });
 
@@ -514,7 +514,7 @@ describe('PrometheusDatasource', () => {
       });
 
       it('should return pipe separated values if the value is an array of strings', () => {
-        expect(ds.interpolateQueryExpr(['a|bc', 'de|f'], customVariable)).toEqual('a\\\\|bc|de\\\\|f');
+        expect(ds.interpolateQueryExpr(['a|bc', 'de|f'], customVariable)).toEqual('(a\\\\|bc|de\\\\|f)');
       });
     });
   });

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

@@ -159,7 +159,7 @@ export class PrometheusDatasource extends DataSourceApi<PromQuery, PromOptions>
     }
 
     const escapedValues = value.map(val => prometheusSpecialRegexEscape(val));
-    return escapedValues.join('|');
+    return '(' + escapedValues.join('|') + ')';
   }
 
   targetContainsTemplate(target: PromQuery) {