bumpRadial could be used with multiple points

fixes #191

since bumpRadial is not exported, a visual test is available at https://observablehq.com/@d3/bumpradial-191

Author: Fil

src/curve/bump.js

@@ -48,16 +48,16 @@ class BumpRadial {
   lineEnd() {}
   point(x, y) {
     x = +x, y = +y;
-    if (this._point++ === 0) {
-      this._x0 = x, this._y0 = y;
-    } else {
+    if (this._point++ > 0) {
       const p0 = pointRadial(this._x0, this._y0);
       const p1 = pointRadial(this._x0, this._y0 = (this._y0 + y) / 2);
       const p2 = pointRadial(x, this._y0);
       const p3 = pointRadial(x, y);
       this._context.moveTo(...p0);
       this._context.bezierCurveTo(...p1, ...p2, ...p3);
     }
+    this._x0 = x;
+    this._y0 = y;
   }
 }
 

test/link-test.js

@@ -1,6 +1,6 @@
 import assert from "assert";
 import {path} from "d3-path";
-import {link, linkHorizontal, linkVertical} from "../src/index.js";
+import {link, linkHorizontal, linkVertical, linkRadial} from "../src/index.js";
 import {curveLinear, curveBumpX, curveBumpY} from "../src/index.js";
 import {assertPathEqual} from "./asserts.js";
 
@@ -112,3 +112,13 @@ it("link.context(context) sets the context", () => {
   assert.strictEqual(l({source: [0, 1], target: [2, 3]}), undefined);
   assertPathEqual(p, "M0,1L2,3");
 });
+
+it("linkRadial() works as expected", () => {
+  const l = linkRadial(), l2 = link();
+  assert.strictEqual(l.source(), l2.source());
+  assert.strictEqual(l.target(), l2.target());
+  assert.strictEqual(l.angle(), l2.x());
+  assert.strictEqual(l.radius(), l2.y());
+  assert.strictEqual(l.context(), l2.context());
+  assertPathEqual(l({source: [0, 1], target: [Math.PI/2, 3]}), "M0,-1C0,-2,2,0,3,0");
+});