Allow specifying undefined for options (#2258)

source/core/options.ts

@@ -1078,7 +1078,13 @@ export default class Options {
 				}
 
 				// @ts-expect-error Type 'unknown' is not assignable to type 'never'.
-				this[key as keyof Options] = options[key as keyof Options];
+				const value = options[key as keyof Options];
+				if (value === undefined) {
+					continue;
+				}
+
+				// @ts-expect-error Type 'unknown' is not assignable to type 'never'.
+				this[key as keyof Options] = value;
 
 				push = true;
 			}

test/agent.ts

@@ -205,3 +205,17 @@ test('no socket hung up regression', withServer, async (t, server, got) => {
 
 	agent.destroy();
 });
+
+test('accept undefined agent', withServer, async (t, server, got) => {
+	server.get('/', (_request, response) => {
+		response.end('ok');
+	});
+
+	const undefinedAgent = undefined;
+	t.truthy((await got({
+		https: {
+			rejectUnauthorized: false,
+		},
+		agent: undefinedAgent,
+	})).body);
+});