Fix default perPage option (#239073)

## Summary

FIX: #238789

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---------

Signed-off-by: namest504 <namest504@gmail.com>
Co-authored-by: Jean-Louis Leysens <jeanlouis.leysens@elastic.co>
(cherry picked from commit 97d93ce)

Author: namest504

src/core/packages/saved-objects/api-server-internal/src/lib/point_in_time_finder.test.ts

@@ -9,8 +9,8 @@
 
 import { loggerMock, type MockedLogger } from '@kbn/logging-mocks';
 import type {
-  SavedObjectsFindResult,
   SavedObjectsCreatePointInTimeFinderOptions,
+  SavedObjectsFindResult,
 } from '@kbn/core-saved-objects-api-server';
 import { savedObjectsPointInTimeFinderMock } from '../mocks';
 
@@ -352,6 +352,7 @@ describe('createPointInTimeFinder()', () => {
         sortField: 'updated_at',
         sortOrder: 'desc',
         type: ['visualization'],
+        perPage: 1000,
       }),
       internalOptions
     );
@@ -516,5 +517,40 @@ describe('createPointInTimeFinder()', () => {
       expect(repository.find).toHaveBeenCalledTimes(2);
       expect(repository.closePointInTime).toHaveBeenCalledTimes(2);
     });
+
+    test('applies defaults as expected', async () => {
+      repository.openPointInTimeForType.mockResolvedValueOnce({
+        id: 'abc123',
+      });
+      repository.find.mockResolvedValueOnce({
+        total: 2,
+        saved_objects: mockHits,
+        pit_id: 'abc123',
+        per_page: 2,
+        page: 0,
+      });
+
+      const findOptions: SavedObjectsCreatePointInTimeFinderOptions = {
+        type: ['visualization'],
+        search: 'foo*',
+      };
+
+      const finder = new PointInTimeFinder(findOptions, {
+        logger,
+        client: repository,
+      });
+      await finder.find().next();
+
+      expect(repository.find).toHaveBeenCalledWith(
+        expect.objectContaining({
+          pit: expect.objectContaining({ id: 'abc123', keepAlive: '2m' }),
+          sortField: 'updated_at',
+          sortOrder: 'desc',
+          type: ['visualization'],
+          perPage: 1000,
+        }),
+        undefined
+      );
+    });
   });
 });

src/core/packages/saved-objects/api-server-internal/src/lib/point_in_time_finder.ts

@@ -45,7 +45,7 @@ export class PointInTimeFinder<T = unknown, A = unknown>
 {
   readonly #log: Logger;
   readonly #client: SavedObjectsPointInTimeFinderClient;
-  readonly #findOptions: SavedObjectsFindOptions;
+  readonly #findOptions: SavedObjectsFindOptions & { perPage: number };
   readonly #internalOptions: SavedObjectsFindInternalOptions | undefined;
   #open: boolean = false;
   #pitId?: string;
@@ -91,7 +91,7 @@ export class PointInTimeFinder<T = unknown, A = unknown>
       this.#log.debug(`Collected [${lastResultsCount}] saved objects`);
 
       // Close PIT if this was our last page
-      if (this.#pitId && lastResultsCount < this.#findOptions.perPage!) {
+      if (this.#pitId && lastResultsCount < this.#findOptions.perPage) {
         await this.close();
       }
 
@@ -103,7 +103,7 @@ export class PointInTimeFinder<T = unknown, A = unknown>
 
       // We've reached the end when there are fewer hits than our perPage size,
       // or when `close()` has been called.
-    } while (this.#open && lastResultsCount >= this.#findOptions.perPage!);
+    } while (this.#open && lastResultsCount >= this.#findOptions.perPage);
 
     return;
   }