[v11.4.x] Dashboards: Panel react for timeFrom and timeShift changes using variables (#98659)

* Dashboards: Panels react to `timeFrom` and `timeShift` changes using variables (#98510)

(cherry picked from commit 8f6220707b)

* restore problematic file

* add the required test

---------

Co-authored-by: Sergej-Vlasov <37613182+Sergej-Vlasov@users.noreply.github.com>
Co-authored-by: Sergej-Vlasov <sergej.s.vlasov@gmail.com>

public/app/features/dashboard-scene/scene/PanelTimeRange.test.tsx

@@ -1,7 +1,14 @@
 import { advanceTo, clear } from 'jest-date-mock';
 
 import { dateTime } from '@grafana/data';
-import { SceneCanvasText, SceneFlexItem, SceneFlexLayout, SceneTimeRange } from '@grafana/scenes';
+import {
+  SceneCanvasText,
+  SceneFlexItem,
+  SceneFlexLayout,
+  SceneTimeRange,
+  SceneVariableSet,
+  TestVariable,
+} from '@grafana/scenes';
 
 import { activateFullSceneTree } from '../utils/test-utils';
 
@@ -60,6 +67,36 @@ describe('PanelTimeRange', () => {
     expect(panelTime.state.from).toBe('now-12h');
     expect(panelTime.state.to).toBe('now-2h');
   });
+
+  it('should update timeInfo when timeShift and timeFrom are variable expressions', async () => {
+    const customTimeFrom = new TestVariable({
+      name: 'testFrom',
+      value: '10s',
+    });
+    const customTimeShift = new TestVariable({
+      name: 'testShift',
+      value: '20s',
+    });
+    const panelTime = new PanelTimeRange({ timeFrom: '$testFrom', timeShift: '$testShift' });
+    const panel = new SceneCanvasText({ text: 'Hello', $timeRange: panelTime });
+    const scene = new SceneFlexLayout({
+      $variables: new SceneVariableSet({
+        variables: [customTimeFrom, customTimeShift],
+      }),
+      $timeRange: new SceneTimeRange({ from: 'now-6h', to: 'now' }),
+      children: [new SceneFlexItem({ body: panel })],
+    });
+    activateFullSceneTree(scene);
+
+    expect(panelTime.state.timeInfo).toBe('Last 10 seconds timeshift -20s');
+
+    customTimeFrom.setState({ value: '15s' });
+    customTimeShift.setState({ value: '25s' });
+
+    panelTime.forceRender();
+
+    expect(panelTime.state.timeInfo).toBe('Last 15 seconds timeshift -25s');
+  });
 });
 
 function buildAndActivateSceneFor(panelTime: PanelTimeRange) {

public/app/features/dashboard-scene/scene/PanelTimeRange.tsx

@@ -7,6 +7,7 @@ import {
   SceneTimeRangeLike,
   SceneTimeRangeState,
   SceneTimeRangeTransformerBase,
+  VariableDependencyConfig,
 } from '@grafana/scenes';
 import { Icon, PanelChrome, TimePickerTooltip, Tooltip, useStyles2 } from '@grafana/ui';
 import { TimeOverrideResult } from 'app/features/dashboard/utils/panel';
@@ -33,12 +34,19 @@ export class PanelTimeRange extends SceneTimeRangeTransformerBase<PanelTimeRange
     this.addActivationHandler(() => this._onActivate());
   }
 
+  protected _variableDependency: VariableDependencyConfig<PanelTimeRangeState> = new VariableDependencyConfig(this, {
+    statePaths: ['timeFrom', 'timeShift'],
+  });
+
   private _onActivate() {
     this._subs.add(
-      this.subscribeToState((n, p) => {
-        // Listen to own changes and update time info when required
-        if (n.timeFrom !== p.timeFrom || n.timeShift !== p.timeShift) {
-          const { timeInfo, timeRange } = this.getTimeOverride(this.getAncestorTimeRange().state.value);
+      this.subscribeToState((n) => {
+        const { timeInfo, timeRange } = this.getTimeOverride(this.getAncestorTimeRange().state.value);
+
+        // When timeFrom or timeShift is a variable we cannot compare to previous interpolated value
+        //   therefore we need to compare timeInfo directly and update when required
+        // Note: compare to newState.timeInfo because it is always one behind
+        if (n.timeInfo !== timeInfo) {
           this.setState({ timeInfo, value: timeRange });
         }
       })