[Discover][Alerts] Make alert links shorter (#158582)

- Addresses https://github.com/elastic/kibana/issues/158262

## Summary

This PR makes alert links shorter by removing redundant props from the
encoded state. We should trim it down more in the future. Backporting a
small fix for now.

For testing:
Please follow instructions from this PR description
https://github.com/elastic/kibana/pull/146403

x-pack/plugins/stack_alerts/server/rule_types/es_query/lib/fetch_search_source_query.test.ts

@@ -7,8 +7,11 @@
 
 import { OnlySearchSourceRuleParams } from '../types';
 import { createSearchSourceMock } from '@kbn/data-plugin/common/search/search_source/mocks';
-import { updateSearchSource } from './fetch_search_source_query';
-import { stubbedSavedObjectIndexPattern } from '@kbn/data-views-plugin/common/data_view.stub';
+import { updateSearchSource, getSmallerDataViewSpec } from './fetch_search_source_query';
+import {
+  createStubDataView,
+  stubbedSavedObjectIndexPattern,
+} from '@kbn/data-views-plugin/common/data_view.stub';
 import { DataView } from '@kbn/data-views-plugin/common';
 import { fieldFormatsMock } from '@kbn/field-formats-plugin/common/mocks';
 import { Comparator } from '../../../../common/comparator_types';
@@ -282,4 +285,121 @@ describe('fetchSearchSourceQuery', () => {
       `);
     });
   });
+
+  describe('getSmallerDataViewSpec', () => {
+    it('should remove "count"s but keep other props like "customLabel"', async () => {
+      const fieldsMap = {
+        test1: {
+          name: 'test1',
+          type: 'keyword',
+          aggregatable: true,
+          searchable: true,
+          readFromDocValues: false,
+        },
+        test2: {
+          name: 'test2',
+          type: 'keyword',
+          aggregatable: true,
+          searchable: true,
+          readFromDocValues: false,
+        },
+        test3: {
+          name: 'test3',
+          type: 'keyword',
+          aggregatable: true,
+          searchable: true,
+          readFromDocValues: false,
+        },
+      };
+      expect(
+        getSmallerDataViewSpec(
+          createStubDataView({
+            spec: {
+              id: 'test',
+              title: 'test*',
+              fields: fieldsMap,
+              fieldAttrs: undefined,
+            },
+          })
+        )?.fieldAttrs
+      ).toBeUndefined();
+      expect(
+        getSmallerDataViewSpec(
+          createStubDataView({
+            spec: {
+              id: 'test',
+              title: 'test*',
+              fields: fieldsMap,
+              fieldAttrs: {
+                test1: {
+                  count: 11,
+                },
+                test2: {
+                  count: 12,
+                },
+              },
+            },
+          })
+        )?.fieldAttrs
+      ).toBeUndefined();
+      expect(
+        getSmallerDataViewSpec(
+          createStubDataView({
+            spec: {
+              id: 'test',
+              title: 'test*',
+              fields: fieldsMap,
+              fieldAttrs: {
+                test1: {
+                  count: 11,
+                  customLabel: 'test11',
+                },
+                test2: {
+                  count: 12,
+                },
+              },
+            },
+          })
+        )?.fieldAttrs
+      ).toMatchInlineSnapshot(`
+        Object {
+          "test1": Object {
+            "customLabel": "test11",
+          },
+        }
+      `);
+      expect(
+        getSmallerDataViewSpec(
+          createStubDataView({
+            spec: {
+              id: 'test',
+              title: 'test*',
+              fields: fieldsMap,
+              fieldAttrs: {
+                test1: {
+                  count: 11,
+                  customLabel: 'test11',
+                },
+                test2: {
+                  customLabel: 'test12',
+                },
+                test3: {
+                  count: 30,
+                },
+              },
+            },
+          })
+        )?.fieldAttrs
+      ).toMatchInlineSnapshot(`
+        Object {
+          "test1": Object {
+            "customLabel": "test11",
+          },
+          "test2": Object {
+            "customLabel": "test12",
+          },
+        }
+      `);
+    });
+  });
 });

x-pack/plugins/stack_alerts/server/rule_types/es_query/lib/fetch_search_source_query.ts

@@ -5,6 +5,7 @@
  * 2.0.
  */
 
+import { omit, pickBy, mapValues } from 'lodash';
 import { buildRangeFilter, Filter } from '@kbn/es-query';
 import {
   DataView,
@@ -186,12 +187,15 @@ async function generateLink(
   const updatedFilters = updateFilterReferences(prevFilters, dataViewToUpdate.id!, newDataView.id!);
 
   const redirectUrlParams: DiscoverAppLocatorParams = {
-    dataViewSpec: newDataView.toSpec(false),
+    dataViewSpec: getSmallerDataViewSpec(newDataView),
     filters: updatedFilters,
     query: searchSource.getField('query'),
     timeRange: { from: dateStart, to: dateEnd },
     isAlertResults: true,
   };
+
+  // use `lzCompress` flag for making the link readable during debugging/testing
+  // const redirectUrl = discoverLocator!.getRedirectUrl(redirectUrlParams, { lzCompress: false });
   const redirectUrl = discoverLocator!.getRedirectUrl(redirectUrlParams);
   const [start, end] = redirectUrl.split('/app');
 
@@ -213,3 +217,23 @@ function updateFilterReferences(filters: Filter[], fromDataView: string, toDataV
     }
   });
 }
+
+export function getSmallerDataViewSpec(
+  dataView: DataView
+): DiscoverAppLocatorParams['dataViewSpec'] {
+  const dataViewSpec = dataView.toSpec(false);
+
+  if (dataViewSpec.fieldAttrs) {
+    // remove `count` props
+    dataViewSpec.fieldAttrs = pickBy(
+      mapValues(dataViewSpec.fieldAttrs, (fieldAttrs) => omit(fieldAttrs, 'count')),
+      (trimmedFieldAttrs) => Object.keys(trimmedFieldAttrs).length > 0
+    );
+
+    if (Object.keys(dataViewSpec.fieldAttrs).length === 0) {
+      dataViewSpec.fieldAttrs = undefined;
+    }
+  }
+
+  return dataViewSpec;
+}