From a763fe96da71c617c7cc2022bbe9d0f1605974f0 Mon Sep 17 00:00:00 2001
From: Andrew Seguin <andrewjs@google.com>
Date: Thu, 17 Apr 2025 10:43:42 -0600
Subject: [PATCH] feat(material/table): add API to force datasource to update

---
 src/material/table/table-data-source.ts | 15 ++++++++-
 src/material/table/table.spec.ts        | 44 ++++++++++++++++++++-----
 2 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/src/material/table/table-data-source.ts b/src/material/table/table-data-source.ts
index c19e8e1e921a..e2115ca1e2b2 100644
--- a/src/material/table/table-data-source.ts
+++ b/src/material/table/table-data-source.ts
@@ -53,6 +53,9 @@ export class MatTableDataSource<T, P extends MatPaginator = MatPaginator> extend
   /** Used to react to internal changes of the paginator that are made by the data source itself. */
   private readonly _internalPageChanges = new Subject<void>();
 
+  /** Stream that will force the data source to emit new data. */
+  private readonly _forceEmit = new BehaviorSubject<boolean>(true);
+
   /**
    * Subscription to the changes that should trigger an update to the table's rendered rows, such
    * as filtering, sorting, pagination, or base data changes.
@@ -243,6 +246,16 @@ export class MatTableDataSource<T, P extends MatPaginator = MatPaginator> extend
     this._updateChangeSubscription();
   }
 
+  /**
+   * Forces the data source to emit data to the table based on the current state of the sort
+   * and paginator. This may be necessary if the state of the paginator or sort components have
+   * been changed programmatically through their Inputs, which do not emit Output events that
+   * would otherwise notify a change.
+   */
+  forceEmit(): void {
+    this._forceEmit.next(true);
+  }
+
   /**
    * Subscribe to changes that should trigger an update to the table's rendered rows. When the
    * changes occur, process the current state of the filter, sort, and pagination along with
@@ -267,7 +280,7 @@ export class MatTableDataSource<T, P extends MatPaginator = MatPaginator> extend
       : observableOf(null);
     const dataStream = this._data;
     // Watch for base data or filter changes to provide a filtered set of data.
-    const filteredData = combineLatest([dataStream, this._filter]).pipe(
+    const filteredData = combineLatest([dataStream, this._filter, this._forceEmit]).pipe(
       map(([data]) => this._filterData(data)),
     );
     // Watch for filtered data or sort changes to provide an ordered set of data.
diff --git a/src/material/table/table.spec.ts b/src/material/table/table.spec.ts
index 20debc1c261c..602ce09ccfcd 100644
--- a/src/material/table/table.spec.ts
+++ b/src/material/table/table.spec.ts
@@ -542,15 +542,26 @@ describe('MatTable', () => {
       for (let i = 0; i < 100; i++) {
         component.underlyingDataSource.addData();
       }
-      fixture.detectChanges();
-      flushMicrotasks(); // Resolve promise that updates paginator's length
-      expectTableToMatchContent(tableElement, [
-        ['Column A', 'Column B', 'Column C'],
+      const firstPage = [
         ['a_1', 'b_1', 'c_1'],
         ['a_2', 'b_2', 'c_2'],
         ['a_3', 'b_3', 'c_3'],
         ['a_4', 'b_4', 'c_4'],
         ['a_5', 'b_5', 'c_5'],
+      ];
+      const secondPage = [
+        ['a_6', 'b_6', 'c_6'],
+        ['a_7', 'b_7', 'c_7'],
+        ['a_8', 'b_8', 'c_8'],
+        ['a_9', 'b_9', 'c_9'],
+        ['a_10', 'b_10', 'c_10'],
+      ];
+
+      fixture.detectChanges();
+      flushMicrotasks(); // Resolve promise that updates paginator's length
+      expectTableToMatchContent(tableElement, [
+        ['Column A', 'Column B', 'Column C'],
+        ...firstPage,
         ['Footer A', 'Footer B', 'Footer C'],
       ]);
 
@@ -559,11 +570,26 @@ describe('MatTable', () => {
       fixture.detectChanges();
       expectTableToMatchContent(tableElement, [
         ['Column A', 'Column B', 'Column C'],
-        ['a_6', 'b_6', 'c_6'],
-        ['a_7', 'b_7', 'c_7'],
-        ['a_8', 'b_8', 'c_8'],
-        ['a_9', 'b_9', 'c_9'],
-        ['a_10', 'b_10', 'c_10'],
+        ...secondPage,
+        ['Footer A', 'Footer B', 'Footer C'],
+      ]);
+
+      component.paginator.pageIndex = 0;
+      fixture.detectChanges();
+      // Expect no changes from before since the data source has not been told to check and
+      // the paginator did not send an Output based on the change.
+      expectTableToMatchContent(tableElement, [
+        ['Column A', 'Column B', 'Column C'],
+        ...secondPage,
+        ['Footer A', 'Footer B', 'Footer C'],
+      ]);
+
+      // Use data source's `forceEmit` to update data based on the latest state in the paginator.
+      component.dataSource.forceEmit();
+      fixture.detectChanges();
+      expectTableToMatchContent(tableElement, [
+        ['Column A', 'Column B', 'Column C'],
+        ...firstPage,
         ['Footer A', 'Footer B', 'Footer C'],
       ]);
     }));