Fix Barchart legend calcs when stacking is percent (#61449)

* Fix Barchart legend calcs when stacking is percent

* doc change

* Refactor + tests

public/app/plugins/panel/barchart/BarChartPanel.tsx

@@ -221,7 +221,7 @@ export const BarChartPanel: React.FunctionComponent<Props> = ({
       }
     }
 
-    return <PlotLegend data={info.viz} config={config} maxHeight="35%" maxWidth="60%" {...options.legend} />;
+    return <PlotLegend data={[info.legend]} config={config} maxHeight="35%" maxWidth="60%" {...options.legend} />;
   };
 
   const rawValue = (seriesIdx: number, valueIdx: number) => {

public/app/plugins/panel/barchart/types.ts

@@ -10,6 +10,12 @@ export interface BarChartDisplayValues {
    */
   viz: [DataFrame];
 
+  /**
+   * The fields we can display, first field is X axis.
+   * Contains same data as viz, but without config modifications (e.g: unit override)
+   */
+  legend: DataFrame;
+
   /** Potentialy color by a field value */
   colorByField?: Field;
 }

public/app/plugins/panel/barchart/utils.test.ts

@@ -211,6 +211,19 @@ describe('BarChart utils', () => {
           null,
         ]
       `);
+
+      const displayLegendValuesAsc = assertIsDefined('legend' in result ? result : null).legend;
+      const legendField = displayLegendValuesAsc.fields[1];
+
+      expect(legendField.values.toArray()).toMatchInlineSnapshot(`
+      [
+        -10,
+        null,
+        10,
+        null,
+        null,
+      ]
+    `);
     });
 
     it('should sort fields when legend sortBy and sortDesc are set', () => {
@@ -232,6 +245,12 @@ describe('BarChart utils', () => {
       expect(displayValuesAsc.fields[2].name).toBe('c');
       expect(displayValuesAsc.fields[3].name).toBe('b');
 
+      const displayLegendValuesAsc = assertIsDefined('legend' in resultAsc ? resultAsc : null).legend;
+      expect(displayLegendValuesAsc.fields[0].type).toBe(FieldType.string);
+      expect(displayLegendValuesAsc.fields[1].name).toBe('a');
+      expect(displayLegendValuesAsc.fields[2].name).toBe('c');
+      expect(displayLegendValuesAsc.fields[3].name).toBe('b');
+
       const resultDesc = prepareBarChartDisplayValues([frame], createTheme(), {
         legend: { sortBy: 'Min', sortDesc: true },
       } as PanelOptions);
@@ -240,6 +259,32 @@ describe('BarChart utils', () => {
       expect(displayValuesDesc.fields[1].name).toBe('b');
       expect(displayValuesDesc.fields[2].name).toBe('c');
       expect(displayValuesDesc.fields[3].name).toBe('a');
+
+      const displayLegendValuesDesc = assertIsDefined('legend' in resultDesc ? resultDesc : null).legend;
+      expect(displayLegendValuesDesc.fields[0].type).toBe(FieldType.string);
+      expect(displayLegendValuesDesc.fields[1].name).toBe('b');
+      expect(displayLegendValuesDesc.fields[2].name).toBe('c');
+      expect(displayLegendValuesDesc.fields[3].name).toBe('a');
+    });
+
+    it('should remove unit from legend values when stacking is percent', () => {
+      const frame = new MutableDataFrame({
+        fields: [
+          { name: 'string', type: FieldType.string, values: ['a', 'b', 'c'] },
+          { name: 'a', values: [-10, 20, 10], state: { calcs: { min: -10 } } },
+          { name: 'b', values: [20, 20, 20], state: { calcs: { min: 20 } } },
+          { name: 'c', values: [10, 10, 10], state: { calcs: { min: 10 } } },
+        ],
+      });
+
+      const resultAsc = prepareBarChartDisplayValues([frame], createTheme(), {
+        stacking: StackingMode.Percent,
+      } as PanelOptions);
+      const displayLegendValuesAsc = assertIsDefined('legend' in resultAsc ? resultAsc : null).legend;
+
+      expect(displayLegendValuesAsc.fields[1].config.unit).toBeUndefined();
+      expect(displayLegendValuesAsc.fields[2].config.unit).toBeUndefined();
+      expect(displayLegendValuesAsc.fields[3].config.unit).toBeUndefined();
     });
   });
 });

public/app/plugins/panel/barchart/utils.ts

@@ -490,6 +490,27 @@ export function prepareBarChartDisplayValues(
     );
   }
 
+  let legendFields: Field[] = fields;
+  if (options.stacking === StackingMode.Percent) {
+    legendFields = fields.map((field) => {
+      const alignedFrameField = frame.fields.find((f) => f.name === field.name)!;
+
+      const copy = {
+        ...field,
+        config: {
+          ...alignedFrameField.config,
+        },
+        values: field.values,
+      };
+
+      copy.display = getDisplayProcessor({ field: copy, theme });
+
+      return copy;
+    });
+
+    legendFields.unshift(firstField);
+  }
+
   // String field is first
   fields.unshift(firstField);
 
@@ -502,6 +523,10 @@ export function prepareBarChartDisplayValues(
         fields: fields, // ideally: fields.filter((f) => !Boolean(f.config.custom?.hideFrom?.viz)),
       },
     ],
+    legend: {
+      fields: legendFields,
+      length: firstField.values.length,
+    },
   };
 }