WIP: check if we can remove polar checks

Author: hydrosquall

src/stack.ts

@@ -1,6 +1,6 @@
 import {array, hasOwnProperty, isBoolean} from 'vega-util';
 import {Aggregate, SUM_OPS} from './aggregate.js';
-import {getSecondaryRangeChannel, NonPositionChannel, NONPOSITION_CHANNELS, isPolarPositionChannel} from './channel.js';
+import {getSecondaryRangeChannel, NonPositionChannel, NONPOSITION_CHANNELS} from './channel.js';
 import {
   channelDefType,
   FieldName,
@@ -173,20 +173,19 @@ export function stack(m: Mark | MarkDef, encoding: Encoding<string>): StackPrope
   const groupbyChannels: StackProperties['groupbyChannels'] = [];
   const groupbyFields: Set<FieldName> = new Set();
 
-  if (encoding[dimensionChannel]) {
-    const dimensionDef = encoding[dimensionChannel];
-    const dimensionField = isFieldDef(dimensionDef) ? vgField(dimensionDef, {}) : undefined;
-    const hasSameDimensionAndStackedField = dimensionField && dimensionField === stackedField;
+  const dimensionDef = encoding[dimensionChannel];
+  const dimensionField = isFieldDef(dimensionDef) ? vgField(dimensionDef, {}) : undefined;
+  const hasSameDimensionAndStackedField = dimensionField && dimensionField === stackedField;
 
-    // For polar coordinates, do not set a groupBy when working with quantitative fields.
-    const isPolar = isPolarPositionChannel(fieldChannel) || isPolarPositionChannel(dimensionChannel);
-    const shouldAddPolarGroupBy = !isUnbinnedQuantitative(dimensionDef);
+  // Do not set a groupBy when working with unbinned quantitative fields
+  // This applies to both polar and cartesian coordinates
+  const shouldAddGroupBy = !isUnbinnedQuantitative(dimensionDef);
 
-    if (isPolar ? shouldAddPolarGroupBy : !hasSameDimensionAndStackedField) {
-      // avoid grouping by the stacked field
-      groupbyChannels.push(dimensionChannel);
-      groupbyFields.add(dimensionField);
-    }
+  // If it's binned, we don't need to group by the dimension field, because we will filter out the offset in the end anyway
+  if (shouldAddGroupBy && !hasSameDimensionAndStackedField) {
+    // avoid grouping by the stacked field
+    groupbyChannels.push(dimensionChannel);
+    groupbyFields.add(dimensionField);
   }
 
   const dimensionOffsetChannel = dimensionChannel === 'x' ? 'xOffset' : 'yOffset';