fix(test): handle nullable Worker.onmessage in type constraints and call sites

Worker.onmessage is typed as `((ev: MessageEvent) => any) | null`, so the
existing MethodKeyOf<T> utility (which only maps non-nullable functions) caused
type errors when used with Worker.

Introduce NullableMethodKeyOf<T> that also matches `T[K] extends AnyFn | null`
and apply it to the unimplemented-method list in mock_test.ts.  Add non-null
assertions at the three call sites in cli_test.ts where onmessage is invoked
directly, since the fake worker always provides a value there.

Author: lambdalisue

denops/@denops-private/cli_test.ts

@@ -288,7 +288,7 @@ Deno.test("main()", async (t) => {
         );
 
         await t.step("and the worker stream is closed", async (t) => {
-          fakeWorker.onmessage(new MessageEvent("message", { data: null }));
+          fakeWorker.onmessage!(new MessageEvent("message", { data: null }));
           await delay(0);
 
           await t.step("calls Worker.terminate()", () => {
@@ -453,7 +453,7 @@ Deno.test("main()", async (t) => {
         assertSpyCalls(globalThis_Worker, 1);
         fakeTcpListener.close();
 
-        fakeWorker.onmessage(new MessageEvent("message", { data: null }));
+        fakeWorker.onmessage!(new MessageEvent("message", { data: null }));
         await delay(0);
 
         await t.step("calls Worker.terminate()", () => {
@@ -557,7 +557,7 @@ Deno.test("main()", async (t) => {
         await delay(0);
 
         await t.step("and the worker stream is closed", async (t) => {
-          fakeWorker.onmessage(new MessageEvent("message", { data: null }));
+          fakeWorker.onmessage!(new MessageEvent("message", { data: null }));
           await delay(0);
 
           await t.step("outputs error logs", () => {

tests/denops/testutil/mock_test.ts

@@ -24,6 +24,10 @@ type MethodKeyOf<T extends AnyRecord> = ({
   [K in keyof T]: T[K] extends AnyFn ? K : never;
 })[keyof T];
 
+type NullableMethodKeyOf<T extends AnyRecord> = ({
+  [K in keyof T]: T[K] extends AnyFn | null ? K : never;
+})[keyof T];
+
 type GetterKeyOf<T extends AnyRecord> = ({
   [K in keyof T]: T[K] extends AnyFn ? never : K;
 })[keyof T];
@@ -337,7 +341,7 @@ Deno.test("createFakeWorker()", async (t) => {
         "removeEventListener",
         "dispatchEvent",
         "terminate",
-      ] as const satisfies readonly MethodKeyOf<Worker>[];
+      ] as const satisfies readonly NullableMethodKeyOf<Worker>[];
       for (const key of unimplementedMethods) {
         await t.step(`.${key}()`, () => {
           assertThrows(() => (worker[key] as AnyFn)(), Error, "Unimplemented");