fix: add field from scale-range to aggregate groupby

src/compile/data/aggregate.ts

@@ -7,8 +7,9 @@ import {
   isGeoPositionChannel,
   isScaleChannel
 } from '../../channel';
-import {binRequiresRange, FieldDef, hasBandEnd, isTypedFieldDef, vgField} from '../../channeldef';
+import {binRequiresRange, FieldDef, hasBandEnd, isScaleFieldDef, isTypedFieldDef, vgField} from '../../channeldef';
 import * as log from '../../log';
+import {isFieldRange} from '../../scale';
 import {AggregateTransform} from '../../transform';
 import {Dict, duplicate, hash, keys, replacePathInField, setEqual} from '../../util';
 import {isUnitModel, ModelWithField} from '../model';
@@ -37,6 +38,9 @@ function addDimension(dims: Set<string>, channel: Channel, fieldDef: FieldDef<st
   } else {
     dims.add(vgField(fieldDef));
   }
+  if (isScaleFieldDef(fieldDef) && isFieldRange(fieldDef.scale?.range)) {
+    dims.add(fieldDef.scale.range.field);
+  }
   return dims;
 }
 

src/scale.ts

@@ -1,4 +1,5 @@
 import {
+  isObject,
   RangeEnum,
   ScaleBins,
   ScaleInterpolateEnum,
@@ -439,6 +440,14 @@ export function isDomainUnionWith(domain: Domain): domain is DomainUnionWith {
   return domain && domain['unionWith'];
 }
 
+export interface FieldRange {
+  field: string;
+}
+
+export function isFieldRange(range: any): range is FieldRange {
+  return isObject(range) && 'field' in range;
+}
+
 export interface Scale<ES extends ExprRef | SignalRef = ExprRef | SignalRef> {
   /**
    * The type of scale. Vega-Lite supports the following categories of scale types:

test/compile/data/aggregate.test.ts

@@ -196,6 +196,26 @@ describe('compile/data/aggregate', () => {
       });
     });
 
+    it('should add correct dimension when field is in scale range', () => {
+      const model = parseUnitModel({
+        mark: 'point',
+        encoding: {
+          x: {timeUnit: 'year', field: 'date'},
+          y: {aggregate: 'mean', field: 'Displacement', type: 'quantitative'},
+          color: {field: 'symbol', type: 'nominal', scale: {range: {field: 'color'}}}
+        }
+      });
+
+      const agg = AggregateNode.makeFromEncoding(null, model);
+      expect(agg.assemble()).toEqual({
+        type: 'aggregate',
+        groupby: ['year_date', 'symbol', 'color'],
+        ops: ['mean'],
+        fields: ['Displacement'],
+        as: ['mean_Displacement']
+      });
+    });
+
     it('adds correct measure for argmin/max', () => {
       const model = parseUnitModel({
         mark: 'point',