From 38e64b710bf3b45bcbf51014eb0e1d6275de5325 Mon Sep 17 00:00:00 2001
From: cobyfrombrooklyn-bot <cobyfrombrooklyn@gmail.com>
Date: Sun, 22 Feb 2026 16:02:52 -0500
Subject: [PATCH] Fix splice with single argument throwing RangeError

When calling data.splice(0) with only one argument, _onDataSplice
computed newCount as arguments.length - 2 = -1, which is an invalid
array length. Fixed by using Math.max(0, ...) to clamp to zero.

Fixes #12191
---
 src/core/core.datasetController.js         |  2 +-
 test/specs/core.datasetController.tests.js | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/core/core.datasetController.js b/src/core/core.datasetController.js
index 9b7126a93fd..094cb76b33a 100644
--- a/src/core/core.datasetController.js
+++ b/src/core/core.datasetController.js
@@ -1065,7 +1065,7 @@ export default class DatasetController {
     if (count) {
       this._sync(['_removeElements', start, count]);
     }
-    const newCount = arguments.length - 2;
+    const newCount = Math.max(0, arguments.length - 2);
     if (newCount) {
       this._sync(['_insertElements', start, newCount]);
     }
diff --git a/test/specs/core.datasetController.tests.js b/test/specs/core.datasetController.tests.js
index 18011efcb95..02ca491835c 100644
--- a/test/specs/core.datasetController.tests.js
+++ b/test/specs/core.datasetController.tests.js
@@ -538,6 +538,28 @@ describe('Chart.DatasetController', function() {
     expect(controller.getParsed(2)).toBe(data[2]);
   });
 
+  it('should handle splice with a single argument without throwing (issue #12191)', function() {
+    var data = [0, 1, 2, 3, 4, 5];
+    var chart = acquireChart({
+      type: 'line',
+      data: {
+        datasets: [{
+          data: data,
+        }],
+      },
+    });
+
+    var meta = chart.getDatasetMeta(0);
+
+    expect(function() {
+      data.splice(0);
+      chart.update();
+    }).not.toThrow();
+
+    expect(meta.data.length).toBe(0);
+    expect(data.length).toBe(0);
+  });
+
   it('should re-synchronize metadata when the data object reference changes', function() {
     var data0 = [0, 1, 2, 3, 4, 5];
     var data1 = [6, 7, 8];