Keep current options when a provider passes undefined

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@switchify/scanning",
-  "version": "0.3.0",
+  "version": "0.3.1",
   "description": "Switch scanning for React and React Native, ported from Switchify PC.",
   "license": "AGPL-3.0-only",
   "type": "module",

src/core/controller.ts

@@ -174,7 +174,9 @@ export class ScanController {
   }
 
   setOptions(options: Partial<ScanOptions>): void {
-    const next = resolveOptions({ ...this.scanner.options, ...options });
+    // An option left undefined keeps its current value rather than resetting to the default.
+    const given = Object.fromEntries(Object.entries(options).filter(([, value]) => value !== undefined)) as Partial<ScanOptions>;
+    const next = resolveOptions({ ...this.scanner.options, ...given });
     const current = this.scanner.options;
     if ((Object.keys(next) as (keyof ScanOptions)[]).every((key) => next[key] === current[key])) {
       return;

test/controller.test.ts

@@ -289,3 +289,13 @@ test("an exclusive group confines scanning until it is removed", async () => {
   await Promise.resolve();
   expect(highlight(controller)).toEqual({ kind: "item", id: "page-a" });
 });
+
+test("options left undefined keep their current values", () => {
+  const { controller, clock } = setup({ options: { automatic: false, intervalMs: 700 } });
+  controller.setOptions({ automatic: undefined, intervalMs: undefined, pattern: "linear" });
+  expect(controller.options).toMatchObject({ automatic: false, intervalMs: 700, pattern: "linear" });
+  controller.registerItem("a");
+  controller.flush();
+  controller.start();
+  expect(clock.running()).toBe(false);
+});