[Dashboard] Store Expanded Panel Id in URL

src/plugins/dashboard/public/application/dashboard_app_controller.tsx

@@ -359,10 +359,6 @@ export class DashboardAppController {
         incomingEmbeddable = undefined;
       }
 
-      let expandedPanelId;
-      if (dashboardContainer && !isErrorEmbeddable(dashboardContainer)) {
-        expandedPanelId = dashboardContainer.getInput().expandedPanelId;
-      }
       const shouldShowEditHelp = getShouldShowEditHelp();
       const shouldShowViewHelp = getShouldShowViewHelp();
       const isEmptyInReadonlyMode = shouldShowUnauthorizedEmptyState();
@@ -384,7 +380,7 @@ export class DashboardAppController {
         lastReloadRequestTime,
         title: dashboardStateManager.getTitle(),
         description: dashboardStateManager.getDescription(),
-        expandedPanelId,
+        expandedPanelId: dashboardStateManager.getExpandedPanelId(),
       };
     };
 

src/plugins/dashboard/public/application/dashboard_state.test.ts

@@ -23,6 +23,9 @@ import { getSavedDashboardMock } from './test_helpers';
 import { InputTimeRange, TimefilterContract, TimeRange } from 'src/plugins/data/public';
 import { ViewMode } from 'src/plugins/embeddable/public';
 import { createKbnUrlStateStorage } from 'src/plugins/kibana_utils/public';
+import { DashboardContainer, DashboardContainerInput } from '.';
+import { DashboardContainerOptions } from './embeddable/dashboard_container';
+import { embeddablePluginMock } from '../../../embeddable/public/mocks';
 
 describe('DashboardState', function () {
   let dashboardState: DashboardStateManager;
@@ -48,6 +51,23 @@ describe('DashboardState', function () {
     });
   }
 
+  function initDashboardContainer(initialInput?: Partial<DashboardContainerInput>) {
+    const { doStart } = embeddablePluginMock.createInstance();
+    const defaultInput: DashboardContainerInput = {
+      id: '123',
+      viewMode: ViewMode.EDIT,
+      filters: [] as DashboardContainerInput['filters'],
+      query: {} as DashboardContainerInput['query'],
+      timeRange: {} as DashboardContainerInput['timeRange'],
+      useMargins: true,
+      title: 'ultra awesome test dashboard',
+      isFullScreenMode: false,
+      panels: {} as DashboardContainerInput['panels'],
+    };
+    const input = { ...defaultInput, ...(initialInput ?? {}) };
+    return new DashboardContainer(input, { embeddable: doStart() } as DashboardContainerOptions);
+  }
+
   describe('syncTimefilterWithDashboard', function () {
     test('syncs quick time', function () {
       savedDashboard.timeRestore = true;
@@ -95,6 +115,43 @@ describe('DashboardState', function () {
     });
   });
 
+  describe('Dashboard Container Changes', () => {
+    beforeEach(() => {
+      initDashboardState();
+    });
+
+    test('expanedPanelId in container input casues state update', () => {
+      dashboardState.setExpandedPanelId = jest.fn();
+
+      const dashboardContainer = initDashboardContainer({
+        expandedPanelId: 'theCoolestPanelOnThisDashboard',
+      });
+
+      dashboardState.handleDashboardContainerChanges(dashboardContainer);
+      expect(dashboardState.setExpandedPanelId).toHaveBeenCalledWith(
+        'theCoolestPanelOnThisDashboard'
+      );
+    });
+
+    test('expanedPanelId is not updated when it is the same', () => {
+      dashboardState.setExpandedPanelId = jest
+        .fn()
+        .mockImplementation(dashboardState.setExpandedPanelId);
+
+      const dashboardContainer = initDashboardContainer({
+        expandedPanelId: 'theCoolestPanelOnThisDashboard',
+      });
+
+      dashboardState.handleDashboardContainerChanges(dashboardContainer);
+      dashboardState.handleDashboardContainerChanges(dashboardContainer);
+      expect(dashboardState.setExpandedPanelId).toHaveBeenCalledTimes(1);
+
+      dashboardContainer.updateInput({ expandedPanelId: 'woah it changed' });
+      dashboardState.handleDashboardContainerChanges(dashboardContainer);
+      expect(dashboardState.setExpandedPanelId).toHaveBeenCalledTimes(2);
+    });
+  });
+
   describe('isDirty', function () {
     beforeAll(() => {
       initDashboardState();

src/plugins/dashboard/public/application/dashboard_state_manager.ts

@@ -267,6 +267,10 @@ export class DashboardStateManager {
       this.setFullScreenMode(input.isFullScreenMode);
     }
 
+    if (input.expandedPanelId !== this.getExpandedPanelId()) {
+      this.setExpandedPanelId(input.expandedPanelId);
+    }
+
     if (!_.isEqual(input.query, this.getQuery())) {
       this.setQuery(input.query);
     }
@@ -282,6 +286,14 @@ export class DashboardStateManager {
     this.stateContainer.transitions.set('fullScreenMode', fullScreenMode);
   }
 
+  public getExpandedPanelId() {
+    return this.appState.expandedPanelId;
+  }
+
+  public setExpandedPanelId(expandedPanelId?: string) {
+    this.stateContainer.transitions.set('expandedPanelId', expandedPanelId);
+  }
+
   public setFilters(filters: Filter[]) {
     this.stateContainer.transitions.set('filters', filters);
   }

src/plugins/dashboard/public/types.ts

@@ -89,6 +89,7 @@ export interface DashboardAppState {
   query: Query | string;
   filters: Filter[];
   viewMode: ViewMode;
+  expandedPanelId?: string;
   savedQuery?: string;
 }
 

test/functional/apps/dashboard/panel_expand_toggle.js

@@ -21,6 +21,7 @@ import expect from '@kbn/expect';
 
 export default function ({ getService, getPageObjects }) {
   const retry = getService('retry');
+  const browser = getService('browser');
   const esArchiver = getService('esArchiver');
   const kibanaServer = getService('kibanaServer');
   const dashboardPanelActions = getService('dashboardPanelActions');
@@ -61,5 +62,18 @@ export default function ({ getService, getPageObjects }) {
         expect(panelCountAfterMaxThenMinimize).to.be(panelCount);
       });
     });
+
+    it('minimizes using the browser back button', async () => {
+      const panelCount = await PageObjects.dashboard.getPanelCount();
+
+      await dashboardPanelActions.openContextMenu();
+      await dashboardPanelActions.clickExpandPanelToggle();
+
+      await browser.goBack();
+      await retry.try(async () => {
+        const panelCountAfterMaxThenMinimize = await PageObjects.dashboard.getPanelCount();
+        expect(panelCountAfterMaxThenMinimize).to.be(panelCount);
+      });
+    });
   });
 }