fix(compiler): make sure LanguageService updated with test file information before getting diagnostics for test file (#1507)

Author: ahnpnl

e2e/__cases__/diagnostics/main.spec.ts

@@ -1,11 +1,7 @@
-import { Thing } from "./main";
+import { foo, Thing } from './main';
 
 export const thing: Thing = { a: 1 };
 
-function doTheThing() {
-  return 1 + 2;
-}
-
-it("should do the thing", () => {
-  expect(doTheThing()).toEqual(3);
+test('foo is 42', () => {
+  expect(foo).toBe(42);
 });

e2e/__cases__/diagnostics/main.ts

@@ -1 +1,2 @@
+export const foo = 42
 export type Thing = { a: number, b: number }