From 10ffe753d936c7ba059f2b436afed374bb33d252 Mon Sep 17 00:00:00 2001
From: Jukka Kurkela <jukka.kurkela@gmail.com>
Date: Fri, 6 Nov 2020 15:05:56 +0200
Subject: [PATCH] When data is removed, remove from stacks too (#8013)

* When data is removed, remove from stacks too
* Remove unreferenced metasets
---
 src/core/core.controller.js                | 17 ++++++++-
 src/core/core.datasetController.js         | 29 +++++++++-----
 test/specs/core.datasetController.tests.js | 44 ++++++++++++++++++++++
 3 files changed, 80 insertions(+), 10 deletions(-)

diff --git a/src/core/core.controller.js b/src/core/core.controller.js
index f17aabb3a..6f724a9de 100644
--- a/src/core/core.controller.js
+++ b/src/core/core.controller.js
@@ -362,12 +362,27 @@ class Chart {
 		me._sortedMetasets = metasets.slice(0).sort(compare2Level('order', 'index'));
 	}
 
+	/**
+	 * @private
+	 */
+	_removeUnreferencedMetasets() {
+		const me = this;
+		const datasets = me.data.datasets;
+		me._metasets.forEach((meta, index) => {
+			if (datasets.filter(x => x === meta._dataset).length === 0) {
+				me._destroyDatasetMeta(index);
+			}
+		});
+	}
+
 	buildOrUpdateControllers() {
 		const me = this;
 		const newControllers = [];
 		const datasets = me.data.datasets;
 		let i, ilen;
 
+		me._removeUnreferencedMetasets();
+
 		for (i = 0, ilen = datasets.length; i < ilen; i++) {
 			const dataset = datasets[i];
 			let meta = me.getDatasetMeta(i);
@@ -694,7 +709,7 @@ class Chart {
 		const me = this;
 		const dataset = me.data.datasets[datasetIndex];
 		const metasets = me._metasets;
-		let meta = metasets.filter(x => x._dataset === dataset).pop();
+		let meta = metasets.filter(x => x && x._dataset === dataset).pop();
 
 		if (!meta) {
 			meta = metasets[datasetIndex] = {
diff --git a/src/core/core.datasetController.js b/src/core/core.datasetController.js
index dd92728f7..83566956d 100644
--- a/src/core/core.datasetController.js
+++ b/src/core/core.datasetController.js
@@ -191,6 +191,13 @@ function createDataContext(parent, index, point, element) {
 	});
 }
 
+function clearStacks(meta, items) {
+	items = items || meta._parsed;
+	items.forEach((parsed) => {
+		delete parsed._stacks[meta.vScale.id][meta.index];
+	});
+}
+
 const optionKeys = (optionNames) => isArray(optionNames) ? optionNames : Object.keys(optionNames);
 const optionKey = (key, active) => active ? 'hover' + _capitalize(key) : key;
 const isDirectUpdateMode = (mode) => mode === 'reset' || mode === 'none';
@@ -293,9 +300,13 @@ export default class DatasetController {
 	 * @private
 	 */
 	_destroy() {
+		const meta = this._cachedMeta;
 		if (this._data) {
 			unlistenArrayEvents(this._data, this);
 		}
+		if (meta._stacked) {
+			clearStacks(meta);
+		}
 	}
 
 	/**
@@ -357,9 +368,7 @@ export default class DatasetController {
 		if (meta.stack !== dataset.stack) {
 			stackChanged = true;
 			// remove values from old stack
-			meta._parsed.forEach((parsed) => {
-				delete parsed._stacks[meta.vScale.id][meta.index];
-			});
+			clearStacks(meta);
 			meta.stack = dataset.stack;
 		}
 
@@ -958,15 +967,13 @@ export default class DatasetController {
 	 */
 	_resyncElements() {
 		const me = this;
-		const meta = me._cachedMeta;
-		const numMeta = meta.data.length;
+		const numMeta = me._cachedMeta.data.length;
 		const numData = me._data.length;
 
 		if (numData > numMeta) {
 			me._insertElements(numMeta, numData - numMeta);
 		} else if (numData < numMeta) {
-			meta.data.splice(numData, numMeta - numData);
-			meta._parsed.splice(numData, numMeta - numData);
+			me._removeElements(numData, numMeta - numData);
 		}
 		// Re-parse the old elements (new elements are parsed in _insertElements)
 		me.parse(0, Math.min(numData, numMeta));
@@ -1002,10 +1009,14 @@ export default class DatasetController {
 	 */
 	_removeElements(start, count) {
 		const me = this;
+		const meta = me._cachedMeta;
 		if (me._parsing) {
-			me._cachedMeta._parsed.splice(start, count);
+			const removed = meta._parsed.splice(start, count);
+			if (meta._stacked) {
+				clearStacks(meta, removed);
+			}
 		}
-		me._cachedMeta.data.splice(start, count);
+		meta.data.splice(start, count);
 	}
 
 
diff --git a/test/specs/core.datasetController.tests.js b/test/specs/core.datasetController.tests.js
index 4445324f9..836b219bd 100644
--- a/test/specs/core.datasetController.tests.js
+++ b/test/specs/core.datasetController.tests.js
@@ -519,6 +519,50 @@ describe('Chart.DatasetController', function() {
 		});
 	});
 
+	it('should re-synchronize stacks when data is removed', function() {
+		var chart = acquireChart({
+			type: 'bar',
+			data: {
+				labels: ['a', 'b'],
+				datasets: [{
+					data: [1, 10],
+					stack: '1'
+				}, {
+					data: [2, 20],
+					stack: '2'
+				}, {
+					data: [3, 30],
+					stack: '1'
+				}]
+			}
+		});
+
+		expect(chart._stacks).toEqual({
+			'x.y.1.bar': {
+				0: {0: 1, 2: 3},
+				1: {0: 10, 2: 30}
+			},
+			'x.y.2.bar': {
+				0: {1: 2},
+				1: {1: 20}
+			}
+		});
+
+		chart.data.datasets[2].data = [4];
+		chart.update();
+
+		expect(chart._stacks).toEqual({
+			'x.y.1.bar': {
+				0: {0: 1, 2: 4},
+				1: {0: 10}
+			},
+			'x.y.2.bar': {
+				0: {1: 2},
+				1: {1: 20}
+			}
+		});
+	});
+
 	it('should cleanup attached properties when the reference changes or when the chart is destroyed', function() {
 		var data0 = [0, 1, 2, 3, 4, 5];
 		var data1 = [6, 7, 8];
-- 
2.47.2