[Discover] Fix wrong sort order with empty sort URL parameter

src/plugins/discover/public/application/angular/discover_state.test.ts

@@ -79,6 +79,48 @@ describe('Test discover state', () => {
     expect(state.getPreviousAppState()).toEqual(stateA);
   });
 });
+describe('Test discover initial state sort handling', () => {
+  test('Non-empty sort in URL should not fallback to state defaults', async () => {
+    history = createBrowserHistory();
+    history.push('/#?_a=(sort:!(!(order_date,desc)))');
+
+    state = getState({
+      getStateDefaults: () => ({ sort: [['fallback', 'desc']] }),
+      history,
+      uiSettings: uiSettingsMock,
+    });
+    await state.replaceUrlAppState({});
+    await state.startSync();
+    expect(state.appStateContainer.getState().sort).toMatchInlineSnapshot(`
+      Array [
+        Array [
+          "order_date",
+          "desc",
+        ],
+      ]
+    `);
+  });
+  test('Empty sort in URL should allow fallback state defaults', async () => {
+    history = createBrowserHistory();
+    history.push('/#?_a=(sort:!())');
+
+    state = getState({
+      getStateDefaults: () => ({ sort: [['fallback', 'desc']] }),
+      history,
+      uiSettings: uiSettingsMock,
+    });
+    await state.replaceUrlAppState({});
+    await state.startSync();
+    expect(state.appStateContainer.getState().sort).toMatchInlineSnapshot(`
+      Array [
+        Array [
+          "fallback",
+          "desc",
+        ],
+      ]
+    `);
+  });
+});
 
 describe('Test discover state with legacy migration', () => {
   test('migration of legacy query ', async () => {

src/plugins/discover/public/application/angular/discover_state.ts

@@ -170,13 +170,20 @@ export function getState({
     appStateFromUrl.query = migrateLegacyQuery(appStateFromUrl.query);
   }
 
+  if (appStateFromUrl && appStateFromUrl.sort && !appStateFromUrl.sort.length) {
+    // If there's an empty array given in the URL, the sort prop should be removed
+    // This allows the sort prop to be overwritten with the default sorting
+    delete appStateFromUrl.sort;
+  }
+
   let initialAppState = handleSourceColumnState(
     {
       ...defaultAppState,
       ...appStateFromUrl,
     },
     uiSettings
   );
+
   // todo filter source depending on fields fetching flag (if no columns remain and source fetching is enabled, use default columns)
   let previousAppState: AppState;
   const appStateContainer = createStateContainer<AppState>(initialAppState);

test/functional/apps/discover/_shared_links.ts

@@ -19,6 +19,7 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
   const browser = getService('browser');
   const toasts = getService('toasts');
   const deployment = getService('deployment');
+  const dataGrid = getService('dataGrid');
 
   describe('shared links', function describeIndexTests() {
     let baseUrl: string;
@@ -87,6 +88,32 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
           );
         });
 
+        it('should load snapshot URL with empty sort param correctly', async function () {
+          const expectedUrl =
+            baseUrl +
+            '/app/discover?_t=1453775307251#' +
+            '/?_g=(filters:!(),refreshInterval:(pause:!t,value:0),time' +
+            ":(from:'2015-09-19T06:31:44.000Z',to:'2015-09" +
+            "-23T18:31:44.000Z'))&_a=(columns:!(),filters:!(),index:'logstash-" +
+            "*',interval:auto,query:(language:kuery,query:'')" +
+            ',sort:!())';
+          await browser.navigateTo(expectedUrl);
+          await PageObjects.discover.waitUntilSearchingHasFinished();
+          await retry.waitFor('url to contain default sorting', async () => {
+            // url fallback default sort should have been pushed to URL
+            const url = await browser.getCurrentUrl();
+            return url.includes('sort:!(!(%27@timestamp%27,desc))');
+          });
+
+          const row = await dataGrid.getRow({ rowIndex: 0 });
+          const firstRowText = await Promise.all(
+            row.map(async (cell) => await cell.getVisibleText())
+          );
+
+          // sorting requested by ES should be correct
+          expect(firstRowText).to.contain('Sep 22, 2015 @ 23:50:13.253');
+        });
+
         it('should allow for copying the snapshot URL as a short URL', async function () {
           const re = new RegExp(baseUrl + '/goto/[0-9a-f]{32}$');
           await PageObjects.share.checkShortenUrl();