fix maybeBooleanRange

Author: mbostock

src/scales/ordinal.js

@@ -44,7 +44,7 @@ export function ScaleOrdinal(key, channels, {
     range = range === undefined ? inferSymbolRange(hint) : Array.from(range, maybeSymbol);
   } else if (registry.get(key) === color) {
     if (range === undefined && (type === "ordinal" || type === ordinalImplicit)) {
-      range = maybeBooleanRange(domain, scheme === undefined ? "greys" : scheme);
+      range = maybeBooleanRange(domain, scheme);
       if (range !== undefined) scheme = undefined; // Don’t re-apply scheme.
     }
     if (scheme === undefined && range === undefined) {

src/scales/schemes.js

@@ -189,9 +189,9 @@ export function ordinalRange(scheme, length) {
 // If the specified domain contains only booleans (ignoring null and undefined),
 // returns a corresponding range where false is mapped to the low color and true
 // is mapped to the high color of the specified scheme.
-export function maybeBooleanRange(domain, scheme) {
+export function maybeBooleanRange(domain, scheme = "greys") {
   const range = new Set();
-  const [f, t] = ordinalScheme(scheme)({length: 2});
+  const [f, t] = ordinalRange(scheme, 2);
   for (const value of domain) {
     if (value == null) continue;
     if (value === true) range.add(t);