feat: support async createTransformer

[lachrist]

Simply wrap the only invocation of createTransformer inside an await expression to support async createTransformer.

Summary

fixes #13759

Test plan

• Build passes.
• Add a test case which passes.
• A bunch of e2e tests fails but it is because of my setup.

[SimenB]

thanks!

[SimenB]

We don't have TLA. This is synchronous anyways, just cast it or something

[lachrist]

@SimenB Right, I forgot to typecheck tests. There was also a failure with windows but I'm not sure what it was. Thanks for your help on this!

[SimenB]

Windows is a bit flaky

[SimenB]

Still an eslint error - run yarn lint-ts-files to see it

[SimenB]

You can apply this diff to fix it:

diff --git c/packages/jest-transform/src/__tests__/ScriptTransformer.test.ts w/packages/jest-transform/src/__tests__/ScriptTransformer.test.ts
index cd8e72c335..5dcbafa28d 100644
--- c/packages/jest-transform/src/__tests__/ScriptTransformer.test.ts
+++ w/packages/jest-transform/src/__tests__/ScriptTransformer.test.ts
@@ -237,8 +237,10 @@ jest.mock(
 jest.mock(
   'async-factory',
   () => ({
-    async createTransformer() {
-      return {process: jest.fn().mockReturnValue({code: 'code'})};
+    createTransformer() {
+      return Promise.resolve({
+        process: jest.fn().mockReturnValue({code: 'code'}),
+      });
     },
   }),
   {virtual: true},

I'm not allowed to push to your branch, otherwise I'd do it myself 🙂

[lachrist]

@SimenB done, sorry for the delay.

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