DataSourceWithBackend: apply template variables (#22558)

packages/grafana-runtime/src/utils/DataSourceWithBackend.ts

@@ -44,7 +44,7 @@ export class DataSourceWithBackend<
         throw new Error('Unknown Datasource: ' + q.datasource);
       }
       return {
-        ...q,
+        ...this.applyTemplateVariables(q),
         datasourceId: ds.id,
         intervalMs,
         maxDataPoints,
@@ -70,6 +70,13 @@ export class DataSourceWithBackend<
     return from(req);
   }
 
+  /**
+   * Override to apply template variables
+   */
+  applyTemplateVariables(query: DataQuery) {
+    return query;
+  }
+
   /**
    * This makes the arrow library loading async.
    */