From 264816c5be1f1103249a07104a23c600a94bb58b Mon Sep 17 00:00:00 2001
From: Abhijit Shyamal <abhijitshyamal005@gmail.com>
Date: Wed, 7 Jan 2026 16:48:58 +0530
Subject: [PATCH 1/2] The documentation and type correctness of dataElementType
 #12169

---
 src/core/core.controller.js        | 15 ++++++++++++---
 src/core/core.datasetController.js | 14 +++++++++++---
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/src/core/core.controller.js b/src/core/core.controller.js
index e0408ae212a..4c6bb1cbb71 100644
--- a/src/core/core.controller.js
+++ b/src/core/core.controller.js
@@ -440,10 +440,19 @@ class Chart {
         meta.controller.linkScales();
       } else {
         const ControllerClass = registry.getController(type);
-        const {datasetElementType, dataElementType} = defaults.datasets[type];
+        let defaultDataElementType = defaults.datasets[type].dataElementType;
+        let defaultDatasetElementType = defaults.datasets[type].datasetElementType;
+
+        if (defaultDataElementType === undefined) {
+          defaultDataElementType = ControllerClass.dataElementType;
+        }
+        if (defaultDatasetElementType === undefined) {
+          defaultDatasetElementType = ControllerClass.datasetElementType;
+        }
+
         Object.assign(ControllerClass, {
-          dataElementType: registry.getElement(dataElementType),
-          datasetElementType: datasetElementType && registry.getElement(datasetElementType)
+          dataElementType: defaultDataElementType ? registry.getElement(defaultDataElementType) : defaultDataElementType,
+          datasetElementType: defaultDatasetElementType ? registry.getElement(defaultDatasetElementType) : defaultDatasetElementType
         });
         meta.controller = new ControllerClass(this, i);
         newControllers.push(meta.controller);
diff --git a/src/core/core.datasetController.js b/src/core/core.datasetController.js
index 9b7126a93fd..0f054568719 100644
--- a/src/core/core.datasetController.js
+++ b/src/core/core.datasetController.js
@@ -271,8 +271,8 @@ export default class DatasetController {
     this.supportsDecimation = false;
     this.$context = undefined;
     this._syncList = [];
-    this.datasetElementType = new.target.datasetElementType;
-    this.dataElementType = new.target.dataElementType;
+    this.datasetElementType = valueOrDefault(new.target.datasetElementType, null);
+    this.dataElementType = valueOrDefault(new.target.dataElementType, null);
 
     this.initialize();
   }
@@ -786,6 +786,9 @@ export default class DatasetController {
 	 * @protected
 	 */
   resolveDatasetElementOptions(mode) {
+    if (!this.datasetElementType) {
+      return {};
+    }
     return this._resolveElementOptions(this.datasetElementType.id, mode);
   }
 
@@ -795,6 +798,9 @@ export default class DatasetController {
 	 * @protected
 	 */
   resolveDataElementOptions(index, mode) {
+    if (!this.dataElementType) {
+      return {};
+    }
     return this._resolveElementOptions(this.dataElementType.id, mode, index);
   }
 
@@ -982,7 +988,9 @@ export default class DatasetController {
     }
 
     if (numData > numMeta) {
-      this._insertElements(numMeta, numData - numMeta, resetNewElements);
+      if (this.dataElementType) {
+        this._insertElements(numMeta, numData - numMeta, resetNewElements);
+      }
     } else if (numData < numMeta) {
       this._removeElements(numData, numMeta - numData);
     }

From 68255660d3f8df034d368a0457927bc374280778 Mon Sep 17 00:00:00 2001
From: Abhijit Shyamal <abhijitshyamal005@gmail.com>
Date: Wed, 7 Jan 2026 16:50:23 +0530
Subject: [PATCH 2/2] soluction.patch

---
 solution.patch | Bin 0 -> 6200 bytes
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 solution.patch

diff --git a/solution.patch b/solution.patch
new file mode 100644
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