fix: don't set default x/y channels when brush has no data

Plot.brush() without data should not call maybeTuple, which would set
default channel accessors and require scales to exist.

Author: Fil

src/interactions/brush.js

@@ -313,7 +313,7 @@ export class Brush extends Mark {
 export function brush(data, options = {}) {
   if (arguments.length === 1 && !isIterable(data)) (options = data), (data = undefined);
   let {x, y, ...rest} = options;
-  [x, y] = maybeTuple(x, y);
+  if (data != null) [x, y] = maybeTuple(x, y);
   return new Brush(data, {...rest, x, y});
 }
 

test/brush-test.ts

@@ -395,9 +395,8 @@ it("brushX reused across two plots syncs in data space", () => {
 
 it("two brush marks in the same plot throws", () => {
   assert.throws(() => {
-    const data = [{x: 1, y: 1}];
     Plot.plot({
-      marks: [Plot.dot(data, {x: "x", y: "y"}), Plot.brush(), Plot.brush()]
+      marks: [Plot.brush(), Plot.brush()]
     });
   }, /only one brush per plot/);
 });