Only enable the bar borderRadius at the end of the stacks

src/controllers/controller.bar.js

@@ -269,10 +269,13 @@ export default class BarController extends DatasetController {
       const parsed = me.getParsed(i);
       const vpixels = reset || isNullOrUndef(parsed[vScale.axis]) ? {base, head: base} : me._calculateBarValuePixels(i);
       const ipixels = me._calculateBarIndexPixels(i, ruler);
+      const stack = me.getStack(i);
 
       const properties = {
         horizontal,
         base: vpixels.base,
+        endOfStack: me.index === stack._top || me.index === stack._bottom,
+        float: isFloatBar(parsed._custom),
         x: horizontal ? vpixels.head : ipixels.center,
         y: horizontal ? ipixels.center : vpixels.head,
         height: horizontal ? ipixels.size : undefined,

src/core/core.datasetController.js

@@ -127,6 +127,11 @@ function getOrCreateStack(stacks, stackKey, indexValue) {
   return subStack[indexValue] || (subStack[indexValue] = {});
 }
 
+function getLastIndexInStack(stack, positive) {
+  const items = Object.entries(stack).filter(([key, v]) => key !== '_top' && key !== '_bottom').filter(([dsIndex, value]) => positive ? value > 0 : value < 0).reverse();
+  return items.length ? parseInt(items[0][0], 10) : null;
+}
+
 function updateStacks(controller, parsed) {
   const {chart, _cachedMeta: meta} = controller;
   const stacks = chart._stacks || (chart._stacks = {}); // map structure is {stackKey: {datasetIndex: value}}
@@ -143,6 +148,9 @@ function updateStacks(controller, parsed) {
     const itemStacks = item._stacks || (item._stacks = {});
     stack = itemStacks[vAxis] = getOrCreateStack(stacks, key, index);
     stack[datasetIndex] = value;
+
+    stack._top = getLastIndexInStack(stack, true);
+    stack._bottom = getLastIndexInStack(stack, false);
   }
 }
 
@@ -533,6 +541,15 @@ export default class DatasetController {
     return applyStack(stack, value, meta.index, {mode});
   }
 
+  /**
+   * @protected
+   */
+  getStack(index) {
+    const {iScale, vScale} = this._cachedMeta;
+    const key = getStackKey(iScale, vScale, this._cachedMeta);
+    return this.chart._stacks[key][index];
+  }
+
   /**
 	 * @protected
 	 */

src/elements/element.bar.js

@@ -83,16 +83,19 @@ function parseBorderWidth(bar, maxW, maxH) {
 }
 
 function parseBorderRadius(bar, maxW, maxH) {
+  const {endOfStack, float} = bar.getProps(['endOfStack', 'float']);
   const value = bar.options.borderRadius;
   const o = toTRBLCorners(value);
   const maxR = Math.min(maxW, maxH);
   const skip = parseBorderSkipped(bar);
 
+  const enableBorder = endOfStack || float;
+
   return {
-    topLeft: skipOrLimit(skip.top || skip.left, o.topLeft, 0, maxR),
-    topRight: skipOrLimit(skip.top || skip.right, o.topRight, 0, maxR),
-    bottomLeft: skipOrLimit(skip.bottom || skip.left, o.bottomLeft, 0, maxR),
-    bottomRight: skipOrLimit(skip.bottom || skip.right, o.bottomRight, 0, maxR)
+    topLeft: skipOrLimit(!enableBorder || skip.top || skip.left, o.topLeft, 0, maxR),
+    topRight: skipOrLimit(!enableBorder || skip.top || skip.right, o.topRight, 0, maxR),
+    bottomLeft: skipOrLimit(!enableBorder || skip.bottom || skip.left, o.bottomLeft, 0, maxR),
+    bottomRight: skipOrLimit(!enableBorder || skip.bottom || skip.right, o.bottomRight, 0, maxR)
   };
 }
 
@@ -224,6 +227,7 @@ BarElement.defaults = {
   borderSkipped: 'start',
   borderWidth: 0,
   borderRadius: 0,
+  endOfStack: false,
   pointStyle: undefined
 };