From 6bcfd74e30ac845c14e40b116ca1f0ebdcb97c35 Mon Sep 17 00:00:00 2001
From: Evert Timberg <evert.timberg@gmail.com>
Date: Sun, 18 Jul 2021 10:14:46 -0400
Subject: [PATCH] Allow dataset specific ChartMeta type extensions

---
 types/index.esm.d.ts                          | 35 +++++++++++++++----
 .../tests/controllers/doughnut_meta_total.ts  | 16 +++++++++
 2 files changed, 45 insertions(+), 6 deletions(-)
 create mode 100644 types/tests/controllers/doughnut_meta_total.ts

diff --git a/types/index.esm.d.ts b/types/index.esm.d.ts
index 5e5b12f5e43..dcbe8188bb8 100644
--- a/types/index.esm.d.ts
+++ b/types/index.esm.d.ts
@@ -327,11 +327,16 @@ export const DoughnutController: ChartComponent & {
   new (chart: Chart, datasetIndex: number): DoughnutController;
 };
 
+export interface DoughnutMetaExtensions {
+  total: number;
+}
+
 export type PieControllerDatasetOptions = DoughnutControllerDatasetOptions;
 export type PieControllerChartOptions = DoughnutControllerChartOptions;
 export type PieAnimationOptions = DoughnutAnimationOptions;
 
 export type PieDataPoint = DoughnutDataPoint;
+export type PieMetaExtensions = DoughnutMetaExtensions;
 
 export type PieController = DoughnutController
 export const PieController: ChartComponent & {
@@ -401,7 +406,7 @@ export const RadarController: ChartComponent & {
   prototype: RadarController;
   new (chart: Chart, datasetIndex: number): RadarController;
 };
-export interface ChartMeta<TElement extends Element = Element, TDatasetElement extends Element = Element> {
+interface ChartMetaCommon<TElement extends Element = Element, TDatasetElement extends Element = Element> {
   type: string;
   controller: DatasetController;
   order: number;
@@ -436,6 +441,16 @@ export interface ChartMeta<TElement extends Element = Element, TDatasetElement e
   _parsed: unknown[];
 }
 
+export type ChartMeta<
+  TElement extends Element = Element,
+  TDatasetElement extends Element = Element,
+  // TODO - V4, move this to the first parameter.
+  // When this was introduced, doing so was a breaking change
+  TType extends ChartType = ChartType,
+> = DeepPartial<
+  { [key in ChartType]: ChartTypeRegistry[key]['metaExtensions'] }[TType]
+> & ChartMetaCommon<TElement, TDatasetElement>;
+
 export interface ActiveDataPoint {
   datasetIndex: number;
   index: number;
@@ -547,7 +562,7 @@ export class DatasetController<
 
   readonly chart: Chart;
   readonly index: number;
-  readonly _cachedMeta: ChartMeta<TElement, TDatasetElement>;
+  readonly _cachedMeta: ChartMeta<TElement, TDatasetElement, TType>;
   enableOptionSharing: boolean;
 
   linkScales(): void;
@@ -560,7 +575,7 @@ export class DatasetController<
   draw(): void;
   reset(): void;
   getDataset(): ChartDataset;
-  getMeta(): ChartMeta<TElement, TDatasetElement>;
+  getMeta(): ChartMeta<TElement, TDatasetElement, TType>;
   getScaleForId(scaleID: string): Scale | undefined;
   configure(): void;
   initialize(): void;
@@ -596,9 +611,9 @@ export class DatasetController<
   setHoverStyle(element: TElement, datasetIndex: number, index: number): void;
 
   parse(start: number, count: number): void;
-  protected parsePrimitiveData(meta: ChartMeta<TElement, TDatasetElement>, data: AnyObject[], start: number, count: number): AnyObject[];
-  protected parseArrayData(meta: ChartMeta<TElement, TDatasetElement>, data: AnyObject[], start: number, count: number): AnyObject[];
-  protected parseObjectData(meta: ChartMeta<TElement, TDatasetElement>, data: AnyObject[], start: number, count: number): AnyObject[];
+  protected parsePrimitiveData(meta: ChartMeta<TElement, TDatasetElement, TType>, data: AnyObject[], start: number, count: number): AnyObject[];
+  protected parseArrayData(meta: ChartMeta<TElement, TDatasetElement, TType>, data: AnyObject[], start: number, count: number): AnyObject[];
+  protected parseObjectData(meta: ChartMeta<TElement, TDatasetElement, TType>, data: AnyObject[], start: number, count: number): AnyObject[];
   protected getParsed(index: number): TParsedData;
   protected applyStack(scale: Scale, parsed: unknown[]): number;
   protected updateRangeFromParsed(
@@ -3335,6 +3350,7 @@ export interface ChartTypeRegistry {
     chartOptions: BarControllerChartOptions;
     datasetOptions: BarControllerDatasetOptions;
     defaultDataPoint: number;
+    metaExtensions: {};
     parsedDataType: BarParsedData,
     scales: keyof CartesianScaleTypeRegistry;
   };
@@ -3342,6 +3358,7 @@ export interface ChartTypeRegistry {
     chartOptions: LineControllerChartOptions;
     datasetOptions: LineControllerDatasetOptions & FillerControllerDatasetOptions;
     defaultDataPoint: ScatterDataPoint | number | null;
+    metaExtensions: {};
     parsedDataType: CartesianParsedData;
     scales: keyof CartesianScaleTypeRegistry;
   };
@@ -3349,6 +3366,7 @@ export interface ChartTypeRegistry {
     chartOptions: ScatterControllerChartOptions;
     datasetOptions: ScatterControllerDatasetOptions;
     defaultDataPoint: ScatterDataPoint | number | null;
+    metaExtensions: {};
     parsedDataType: CartesianParsedData;
     scales: keyof CartesianScaleTypeRegistry;
   };
@@ -3356,6 +3374,7 @@ export interface ChartTypeRegistry {
     chartOptions: unknown;
     datasetOptions: BubbleControllerDatasetOptions;
     defaultDataPoint: BubbleDataPoint;
+    metaExtensions: {};
     parsedDataType: BubbleParsedData;
     scales: keyof CartesianScaleTypeRegistry;
   };
@@ -3363,6 +3382,7 @@ export interface ChartTypeRegistry {
     chartOptions: PieControllerChartOptions;
     datasetOptions: PieControllerDatasetOptions;
     defaultDataPoint: PieDataPoint;
+    metaExtensions: PieMetaExtensions;
     parsedDataType: number;
     scales: keyof CartesianScaleTypeRegistry;
   };
@@ -3370,6 +3390,7 @@ export interface ChartTypeRegistry {
     chartOptions: DoughnutControllerChartOptions;
     datasetOptions: DoughnutControllerDatasetOptions;
     defaultDataPoint: DoughnutDataPoint;
+    metaExtensions: DoughnutMetaExtensions;
     parsedDataType: number;
     scales: keyof CartesianScaleTypeRegistry;
   };
@@ -3377,6 +3398,7 @@ export interface ChartTypeRegistry {
     chartOptions: PolarAreaControllerChartOptions;
     datasetOptions: PolarAreaControllerDatasetOptions;
     defaultDataPoint: number;
+    metaExtensions: {};
     parsedDataType: RadialParsedData;
     scales: keyof RadialScaleTypeRegistry;
   };
@@ -3384,6 +3406,7 @@ export interface ChartTypeRegistry {
     chartOptions: RadarControllerChartOptions;
     datasetOptions: RadarControllerDatasetOptions & FillerControllerDatasetOptions;
     defaultDataPoint: number | null;
+    metaExtensions: {};
     parsedDataType: RadialParsedData;
     scales: keyof RadialScaleTypeRegistry;
   };
diff --git a/types/tests/controllers/doughnut_meta_total.ts b/types/tests/controllers/doughnut_meta_total.ts
new file mode 100644
index 00000000000..5a57295ce8e
--- /dev/null
+++ b/types/tests/controllers/doughnut_meta_total.ts
@@ -0,0 +1,16 @@
+import { Chart, ChartMeta, Element } from '../../index.esm';
+
+const chart = new Chart('id', {
+  type: 'doughnut',
+  data: {
+    labels: [],
+    datasets: [{
+      data: [],
+    }]
+  },
+});
+
+// A cast is required because the exact type of ChartMeta will vary with
+// mixed charts
+const meta = <ChartMeta<Element, Element, 'doughnut'>>chart.getDatasetMeta(0);
+const total = meta.total;