VizPanelManager: Load default/last used data source if no data source specified for a panel (#84999)

public/app/features/dashboard-scene/panel-edit/VizPanelManager.test.tsx

@@ -179,7 +179,14 @@ describe('VizPanelManager', () => {
         title: 'Panel A',
         key: 'panel-1',
         pluginId: 'table',
-        $data: new SceneQueryRunner({ key: 'data-query-runner', queries: [{ refId: 'A' }] }),
+        $data: new SceneQueryRunner({
+          key: 'data-query-runner',
+          datasource: {
+            type: 'grafana-testdata-datasource',
+            uid: 'gdev-testdata',
+          },
+          queries: [{ refId: 'A' }],
+        }),
         options: undefined,
         fieldConfig: {
           defaults: {
@@ -210,7 +217,14 @@ describe('VizPanelManager', () => {
         title: 'Panel A',
         key: 'panel-1',
         pluginId: 'table',
-        $data: new SceneQueryRunner({ key: 'data-query-runner', queries: [{ refId: 'A' }] }),
+        $data: new SceneQueryRunner({
+          key: 'data-query-runner',
+          datasource: {
+            type: 'grafana-testdata-datasource',
+            uid: 'gdev-testdata',
+          },
+          queries: [{ refId: 'A' }],
+        }),
         options: {
           customOption: 'A',
         },
@@ -719,6 +733,23 @@ describe('VizPanelManager', () => {
       });
     });
   });
+
+  it('should load last used data source if no data source specified for a panel', async () => {
+    store.exists.mockReturnValue(true);
+    store.getObject.mockReturnValue({
+      dashboardUid: 'ffbe00e2-803c-4d49-adb7-41aad336234f',
+      datasourceUid: 'gdev-testdata',
+    });
+    const { scene, panel } = setupTest('panel-5');
+    scene.setState({ editPanel: buildPanelEditScene(panel) });
+
+    const vizPanelManager = scene.state.editPanel!.state.vizManager;
+    vizPanelManager.activate();
+    await Promise.resolve();
+
+    expect(vizPanelManager.state.datasource).toEqual(ds1Mock);
+    expect(vizPanelManager.state.dsSettings).toEqual(instance1SettingsMock);
+  });
 });
 
 const setupTest = (panelId: string) => {

public/app/features/dashboard-scene/panel-edit/VizPanelManager.tsx

@@ -108,15 +108,37 @@ export class VizPanelManager extends SceneObjectBase<VizPanelManagerState> {
 
     let datasourceToLoad = this.queryRunner.state.datasource;
 
-    if (!datasourceToLoad) {
-      return;
-    }
-
     try {
-      // TODO: Handle default/last used datasource selection for new panel
-      // Ref: PanelEditorQueries / componentDidMount
-      const datasource = await getDataSourceSrv().get(datasourceToLoad);
-      const dsSettings = getDataSourceSrv().getInstanceSettings(datasourceToLoad);
+      let datasource: DataSourceApi | undefined;
+      let dsSettings: DataSourceInstanceSettings | undefined;
+
+      if (!datasourceToLoad) {
+        const dashboardScene = getDashboardSceneFor(this);
+        const dashboardUid = dashboardScene.state.uid ?? '';
+        const lastUsedDatasource = getLastUsedDatasourceFromStorage(dashboardUid!);
+
+        // do we have a last used datasource for this dashboard
+        if (lastUsedDatasource?.datasourceUid !== null) {
+          // get datasource from dashbopard uid
+          dsSettings = getDataSourceSrv().getInstanceSettings({ uid: lastUsedDatasource?.datasourceUid });
+          if (dsSettings) {
+            datasource = await getDataSourceSrv().get({
+              uid: lastUsedDatasource?.datasourceUid,
+              type: dsSettings.type,
+            });
+
+            this.queryRunner.setState({
+              datasource: {
+                uid: lastUsedDatasource?.datasourceUid,
+                type: dsSettings.type,
+              },
+            });
+          }
+        }
+      } else {
+        datasource = await getDataSourceSrv().get(datasourceToLoad);
+        dsSettings = getDataSourceSrv().getInstanceSettings(datasourceToLoad);
+      }
 
       if (datasource && dsSettings) {
         this.setState({

public/app/features/dashboard-scene/panel-edit/testfiles/testDashboard.ts

@@ -327,6 +327,89 @@ export const panelWithDashboardQueryAndTransformations = {
   ],
   type: 'table',
 };
+
+export const panelWithNoDataSource = {
+  fieldConfig: {
+    defaults: {
+      color: {
+        mode: 'palette-classic',
+      },
+      custom: {
+        axisBorderShow: false,
+        axisCenteredZero: false,
+        axisColorMode: 'text',
+        axisLabel: '',
+        axisPlacement: 'auto',
+        barAlignment: 0,
+        drawStyle: 'line',
+        fillOpacity: 0,
+        gradientMode: 'none',
+        hideFrom: {
+          legend: false,
+          tooltip: false,
+          viz: false,
+        },
+        insertNulls: false,
+        lineInterpolation: 'linear',
+        lineWidth: 1,
+        pointSize: 5,
+        scaleDistribution: {
+          type: 'linear',
+        },
+        showPoints: 'auto',
+        spanNulls: false,
+        stacking: {
+          group: 'A',
+          mode: 'none',
+        },
+        thresholdsStyle: {
+          mode: 'off',
+        },
+      },
+      mappings: [],
+      thresholds: {
+        mode: 'absolute',
+        steps: [
+          {
+            color: 'green',
+            value: null,
+          },
+          {
+            color: 'red',
+            value: 80,
+          },
+        ],
+      },
+    },
+    overrides: [],
+  },
+  gridPos: {
+    h: 8,
+    w: 12,
+    x: 0,
+    y: 0,
+  },
+  id: 5,
+  options: {
+    legend: {
+      calcs: [],
+      displayMode: 'list',
+      placement: 'bottom',
+      showLegend: true,
+    },
+    tooltip: {
+      mode: 'single',
+      sort: 'none',
+    },
+  },
+  targets: [
+    {
+      refId: 'A',
+    },
+  ],
+  title: 'Panel with no data source',
+  type: 'timeseries',
+};
 export const testDashboard = {
   annotations: {
     list: [
@@ -355,6 +438,7 @@ export const testDashboard = {
     panelWithTransformations,
     panelWithDashboardQuery,
     panelWithDashboardQueryAndTransformations,
+    panelWithNoDataSource,
   ],
   refresh: '',
   schemaVersion: 39,