Panel: Support using $__interval and $__interval_ms in panel title

public/app/features/dashboard/state/PanelModel.test.ts

@@ -233,6 +233,18 @@ describe('PanelModel', () => {
         const out = model.replaceVariables('hello $aaa and $bbb', extra);
         expect(out).toBe('hello XXX and BBB');
       });
+
+      it('Can use request scoped vars', () => {
+        model.getQueryRunner().getLastRequest = () => {
+          return {
+            scopedVars: {
+              __interval: { text: '10m', value: '10m' },
+            },
+          };
+        };
+        const out = model.replaceVariables('hello $__interval');
+        expect(out).toBe('hello 10m');
+      });
     });
 
     describe('when changing panel type', () => {

public/app/features/dashboard/state/PanelModel.ts

@@ -564,26 +564,21 @@ export class PanelModel implements DataConfigSource, IPanelModel {
   }
 
   replaceVariables(value: string, extraVars: ScopedVars | undefined, format?: string | Function) {
-    let vars = this.scopedVars;
-
-    if (extraVars) {
-      vars = vars ? { ...vars, ...extraVars } : extraVars;
-    }
+    const lastRequest = this.getQueryRunner().getLastRequest();
+    const vars: ScopedVars = Object.assign({}, this.scopedVars, lastRequest?.scopedVars, extraVars);
 
     const allVariablesParams = getVariablesUrlParams(vars);
     const variablesQuery = urlUtil.toUrlParams(allVariablesParams);
     const timeRangeUrl = urlUtil.toUrlParams(getTimeSrv().timeRangeForUrl());
 
-    vars = {
-      ...vars,
-      [DataLinkBuiltInVars.keepTime]: {
-        text: timeRangeUrl,
-        value: timeRangeUrl,
-      },
-      [DataLinkBuiltInVars.includeVars]: {
-        text: variablesQuery,
-        value: variablesQuery,
-      },
+    vars[DataLinkBuiltInVars.keepTime] = {
+      text: timeRangeUrl,
+      value: timeRangeUrl,
+    };
+
+    vars[DataLinkBuiltInVars.includeVars] = {
+      text: variablesQuery,
+      value: variablesQuery,
     };
 
     return getTemplateSrv().replace(value, vars, format);
@@ -602,7 +597,7 @@ export class PanelModel implements DataConfigSource, IPanelModel {
    * If you need the raw title without interpolation use title property instead.
    * */
   getDisplayTitle(): string {
-    return this.replaceVariables(this.title, {}, 'text');
+    return this.replaceVariables(this.title, undefined, 'text');
   }
 }
 

public/app/features/query/state/PanelQueryRunner.ts

@@ -73,6 +73,7 @@ export class PanelQueryRunner {
   private subscription?: Unsubscribable;
   private lastResult?: PanelData;
   private dataConfigSource: DataConfigSource;
+  private lastRequest?: DataQueryRequest;
 
   constructor(dataConfigSource: DataConfigSource) {
     this.subject = new ReplaySubject(1);
@@ -251,6 +252,8 @@ export class PanelQueryRunner {
       request.interval = norm.interval;
       request.intervalMs = norm.intervalMs;
 
+      this.lastRequest = request;
+
       this.pipeToSubject(runRequest(ds, request), panelId);
     } catch (err) {
       console.error('PanelQueryRunner Error', err);
@@ -333,6 +336,10 @@ export class PanelQueryRunner {
   getLastResult(): PanelData | undefined {
     return this.lastResult;
   }
+
+  getLastRequest(): DataQueryRequest | undefined {
+    return this.lastRequest;
+  }
 }
 
 async function getDataSource(