channel label override (observablehq#1838)

Author: mbostock

src/mark.js

@@ -46,9 +46,9 @@ export class Mark {
       Object.entries(channels)
         .map(([name, channel]) => {
           if (isOptions(channel.value)) {
-            // apply scale overrides
-            const {value, scale = channel.scale} = channel.value;
-            channel = {...channel, scale, value};
+            // apply scale and label overrides
+            const {value, label = channel.label, scale = channel.scale} = channel.value;
+            channel = {...channel, label, scale, value};
           }
           if (data === singleton && typeof channel.value === "string") {
             // convert field names to singleton values for decoration marks (e.g., frame)

test/plots/tip-format.ts

@@ -61,7 +61,7 @@ export async function tipFormatPairedLabel() {
 }
 
 export async function tipFormatPairedLabelChannel() {
-  return tip({length: 1}, {x1: Object.assign([0], {label: "Low"}), x2: Object.assign([1], {label: "High"})});
+  return tip({length: 1}, {x1: {value: [0], label: "Low"}, x2: {value: [1], label: "High"}});
 }
 
 export async function tipFormatPairedLabelScale() {