Prometheus: Fix bug when adding a query in mixed datasource (#69424)

default query needs to not be a function separate from ds

public/app/plugins/datasource/prometheus/datasource.tsx

@@ -1265,7 +1265,12 @@ export class PrometheusDatasource
   }
 
   getDefaultQuery(app: CoreApp): PromQuery {
-    const defaults = promDefaultBaseQuery();
+    const defaults = {
+      refId: 'A',
+      expr: '',
+      range: true,
+      instant: false,
+    };
 
     if (app === CoreApp.UnifiedAlerting) {
       return {
@@ -1335,12 +1340,3 @@ export function prometheusRegularEscape(value: any) {
 export function prometheusSpecialRegexEscape(value: any) {
   return typeof value === 'string' ? value.replace(/\\/g, '\\\\\\\\').replace(/[$^*{}\[\]\'+?.()|]/g, '\\\\$&') : value;
 }
-
-export function promDefaultBaseQuery(): PromQuery {
-  return {
-    refId: 'A',
-    expr: '',
-    range: true,
-    instant: false,
-  };
-}

public/app/plugins/datasource/prometheus/querybuilder/components/PromQueryBuilderOptions.test.tsx

@@ -5,7 +5,6 @@ import { selectOptionInTest } from 'test/helpers/selectOptionInTest';
 
 import { CoreApp } from '@grafana/data';
 
-import { promDefaultBaseQuery } from '../../datasource';
 import { PromQuery } from '../../types';
 import { getQueryWithDefaults } from '../state';
 
@@ -107,7 +106,15 @@ function setup(queryOverrides: Partial<PromQuery> = {}, app: CoreApp = CoreApp.P
   const props = {
     app,
     query: {
-      ...getQueryWithDefaults(promDefaultBaseQuery(), CoreApp.PanelEditor),
+      ...getQueryWithDefaults(
+        {
+          refId: 'A',
+          expr: '',
+          range: true,
+          instant: false,
+        } as PromQuery,
+        CoreApp.PanelEditor
+      ),
       ...queryOverrides,
     },
     onRunQuery: jest.fn(),