[8.14] [Discover] Fix resetting of breakdown field in a saved search (#…

…184668) (#184998)

# Backport

This will backport the following commits from `main` to `8.14`:
- [[Discover] Fix resetting of breakdown field in a saved search
(#184668)](#184668)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Julia
Rechkunova","email":"julia.rechkunova@elastic.co"},"sourceCommit":{"committedDate":"2024-06-07T11:29:16Z","message":"[Discover]
Fix resetting of breakdown field in a saved search (#184668)\n\n- Closes
https://github.com/elastic/kibana/issues/184379\r\n\r\n##
Summary\r\n\r\nThis PR brings back the logic which was edited
in\r\nhttps://github.com//pull/169548 This should allow to
reset\r\nthe saved breakdown field with rather an empty string as
`undefined`\r\nseems to be ignored.\r\n\r\n### Checklist\r\n\r\n- [x]
[Unit or
functional\r\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\r\nwere
updated or added to match the most common
scenarios","sha":"132ab34ba54fbc6d119bc1e31d3838cd72493082","branchLabelMapping":{"^v8.15.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["Feature:Discover","release_note:fix","Team:DataDiscovery","backport:prev-minor","v8.15.0"],"title":"[Discover]
Fix resetting of breakdown field in a saved
search","number":184668,"url":"https://github.com/elastic/kibana/pull/184668","mergeCommit":{"message":"[Discover]
Fix resetting of breakdown field in a saved search (#184668)\n\n- Closes
https://github.com/elastic/kibana/issues/184379\r\n\r\n##
Summary\r\n\r\nThis PR brings back the logic which was edited
in\r\nhttps://github.com//pull/169548 This should allow to
reset\r\nthe saved breakdown field with rather an empty string as
`undefined`\r\nseems to be ignored.\r\n\r\n### Checklist\r\n\r\n- [x]
[Unit or
functional\r\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\r\nwere
updated or added to match the most common
scenarios","sha":"132ab34ba54fbc6d119bc1e31d3838cd72493082"}},"sourceBranch":"main","suggestedTargetBranches":[],"targetPullRequestStates":[{"branch":"main","label":"v8.15.0","branchLabelMappingKey":"^v8.15.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/184668","number":184668,"mergeCommit":{"message":"[Discover]
Fix resetting of breakdown field in a saved search (#184668)\n\n- Closes
https://github.com/elastic/kibana/issues/184379\r\n\r\n##
Summary\r\n\r\nThis PR brings back the logic which was edited
in\r\nhttps://github.com//pull/169548 This should allow to
reset\r\nthe saved breakdown field with rather an empty string as
`undefined`\r\nseems to be ignored.\r\n\r\n### Checklist\r\n\r\n- [x]
[Unit or
functional\r\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\r\nwere
updated or added to match the most common
scenarios","sha":"132ab34ba54fbc6d119bc1e31d3838cd72493082"}}]}]
BACKPORT-->

Co-authored-by: Julia Rechkunova <julia.rechkunova@elastic.co>

src/plugins/discover/public/application/main/services/discover_saved_search_container.ts

@@ -402,6 +402,10 @@ function getSavedSearchFieldForComparison(
     return visContext;
   }
 
+  if (fieldName === 'breakdownField') {
+    return savedSearch.breakdownField || ''; // ignore the difference between an empty string and undefined
+  }
+
   return savedSearch[fieldName];
 }
 

src/plugins/discover/public/application/main/services/discover_state.test.ts

@@ -434,7 +434,6 @@ describe('Test discover state actions', () => {
     const { searchSource, ...savedSearch } = state.savedSearchState.getState();
     expect(savedSearch).toMatchInlineSnapshot(`
       Object {
-        "breakdownField": undefined,
         "columns": Array [
           "default_column",
         ],

src/plugins/discover/public/application/main/utils/update_saved_search.test.ts

@@ -124,6 +124,40 @@ describe('updateSavedSearch', () => {
     });
   });
 
+  it('should pass breakdownField if state has breakdownField', async () => {
+    const savedSearch = {
+      ...savedSearchMock,
+      searchSource: savedSearchMock.searchSource.createCopy(),
+    };
+    expect(savedSearch.breakdownField).toBeUndefined();
+    updateSavedSearch({
+      savedSearch,
+      globalStateContainer: createGlobalStateContainer(),
+      services: discoverServiceMock,
+      state: {
+        breakdownField: 'test',
+      },
+    });
+    expect(savedSearch.breakdownField).toEqual('test');
+  });
+
+  it('should pass an empty string if state already has breakdownField', async () => {
+    const savedSearch = {
+      ...savedSearchMock,
+      searchSource: savedSearchMock.searchSource.createCopy(),
+      breakdownField: 'test',
+    };
+    updateSavedSearch({
+      savedSearch,
+      globalStateContainer: createGlobalStateContainer(),
+      services: discoverServiceMock,
+      state: {
+        breakdownField: undefined,
+      },
+    });
+    expect(savedSearch.breakdownField).toEqual('');
+  });
+
   it('should set query and filters from services', async () => {
     const savedSearch = {
       ...savedSearchMock,

src/plugins/discover/public/application/main/utils/update_saved_search.ts

@@ -73,7 +73,12 @@ export function updateSavedSearch({
       savedSearch.viewMode = state.viewMode;
     }
 
-    savedSearch.breakdownField = state.breakdownField || undefined; // `undefined` instead of an empty string
+    if (typeof state.breakdownField !== 'undefined') {
+      savedSearch.breakdownField = state.breakdownField;
+    } else if (savedSearch.breakdownField) {
+      savedSearch.breakdownField = '';
+    }
+
     savedSearch.hideAggregatedPreview = state.hideAggregatedPreview;
 
     // add a flag here to identify text based language queries