don’t subgroup if output

Author: mbostock

src/transforms/bin.js

@@ -1,8 +1,7 @@
 import {bin as binner} from "d3";
-import {firstof} from "../defined.js";
 import {valueof, range, identity, maybeLazyChannel, maybeTransform, maybeTuple, maybeColor, maybeValue, mid, labelof} from "../mark.js";
 import {offset} from "../style.js";
-import {maybeGroup, maybeGroupOutputs, maybeReduce, reduceIdentity} from "./group.js";
+import {maybeGroup, maybeOutputs, maybeReduce, maybeSubgroup, reduceIdentity} from "./group.js";
 
 // Group on {z, fill, stroke}, then optionally on y, then bin x.
 export function binX(outputs, {inset, insetLeft, insetRight, ...options} = {}) {
@@ -62,7 +61,7 @@ function binn(
   bx = maybeBin(bx);
   by = maybeBin(by);
   reduceData = maybeReduce(reduceData, identity);
-  outputs = maybeGroupOutputs(outputs, inputs);
+  outputs = maybeOutputs(outputs, inputs);
 
   // Produce x1, x2, y1, and y2 output channels as appropriate (when binning).
   const [BX1, setBX1] = maybeLazyChannel(bx);
@@ -98,7 +97,7 @@ function binn(
       const Z = valueof(data, z);
       const F = valueof(data, vfill);
       const S = valueof(data, vstroke);
-      const G = firstof(Z, F, S);
+      const G = maybeSubgroup(outputs, Z, F, S);
       const groupFacets = [];
       const groupData = [];
       const GK = K && setGK([]);

src/transforms/group.js

@@ -37,7 +37,7 @@ function groupn(
   inputs = {} // input channels and options
 ) {
   reduceData = maybeReduce(reduceData, identity);
-  outputs = maybeGroupOutputs(outputs, inputs);
+  outputs = maybeOutputs(outputs, inputs);
 
   // Produce x and y output channels as appropriate.
   const [GX, setGX] = maybeLazyChannel(x);
@@ -67,7 +67,7 @@ function groupn(
       const Z = valueof(data, z);
       const F = valueof(data, vfill);
       const S = valueof(data, vstroke);
-      const G = firstof(Z, F, S);
+      const G = maybeSubgroup(outputs, Z, F, S);
       const groupFacets = [];
       const groupData = [];
       const GX = X && setGX([]);
@@ -102,7 +102,7 @@ function groupn(
   };
 }
 
-export function maybeGroupOutputs(outputs, inputs) {
+export function maybeOutputs(outputs, inputs) {
   return Object.entries(outputs).map(([name, reduce]) => {
     const value = maybeInput(name, inputs);
     const reducer = maybeReduce(reduce, value);
@@ -155,6 +155,14 @@ export function maybeReduce(reduce, value) {
   throw new Error("invalid reduce");
 }
 
+export function maybeSubgroup(outputs, Z, F, S) {
+  return firstof(
+    outputs.some(o => o.name === "z") ? undefined : Z,
+    outputs.some(o => o.name === "fill") ? undefined : F,
+    outputs.some(o => o.name === "stroke") ? undefined : S
+  );
+}
+
 function reduceFunction(f) {
   return {
     reduce(I, X) {