Prometheus: Fix fetching label values when datasource has no labels match api support (#72960)

* interpolate match string

* provide unit test

* add the third parameter back to fix the unit test

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

@@ -274,6 +274,27 @@ describe('Language completion provider', () => {
         undefined
       );
     });
+
+    it('should call old series endpoint and should use match[] parameter and interpolate the template variables', () => {
+      const languageProvider = new LanguageProvider({
+        ...defaultDatasource,
+        interpolateString: (string: string) => string.replace(/\$/, 'interpolated-'),
+      } as PrometheusDatasource);
+      const getSeriesValues = languageProvider.getSeriesValues;
+      const requestSpy = jest.spyOn(languageProvider, 'request');
+      getSeriesValues('job', '{instance="$instance", job="grafana"}');
+      expect(requestSpy).toHaveBeenCalled();
+      expect(requestSpy).toHaveBeenCalledWith(
+        '/api/v1/series',
+        [],
+        {
+          end: toPrometheusTimeString,
+          'match[]': '{instance="interpolated-instance", job="grafana"}',
+          start: fromPrometheusTimeString,
+        },
+        undefined
+      );
+    });
   });
 
   describe('fetchSeries', () => {

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

@@ -567,10 +567,11 @@ export default class PromQlLanguageProvider extends LanguageProvider {
    */
   fetchSeriesValuesWithMatch = async (name: string, match?: string): Promise<string[]> => {
     const interpolatedName = name ? this.datasource.interpolateString(name) : null;
+    const interpolatedMatch = match ? this.datasource.interpolateString(match) : null;
     const range = this.datasource.getAdjustedInterval();
     const urlParams = {
       ...range,
-      ...(match && { 'match[]': match }),
+      ...(interpolatedMatch && { 'match[]': interpolatedMatch }),
     };
 
     // @todo clean up prometheusResourceBrowserCache feature flag