How do I debug a failing vi.mock() resolution? It silently can't find __mocks__

[fregante]

I'm calling this in my X.test.ts file:

vi.mock('@org/local-util/file.js');

import injectIframe from "./injectIframe";
...etc

The path matches the imported file (imported in injectIframe.ts) and the mocking "works" (i.e. the source file.js is not executed, as expected) but Vitest is not picking up the manual mock under src/__mocks__/@org/local-util/file.ts

I tried moving that __mocks__ folder higher and lower in the tree, but it still can't find it. I tried changing the extension to .js, I moved it the dist folder, nothing.

I can't find any way to debug this, there's no log of "attempted paths" that I can look at, it just fails to load and proceeds as if the __mocks__ file didn't exist.

How do I debug this?

[fregante]

The solution was to start a node debugger in VS Code and wade my way through the code. There's no debugging/logging anywhere in that function. I ended up on the chunk:

  const dir = dirname(path);
  const baseId = basename(path);
  const fullPath = resolve(dir, "__mocks__", baseId);
  return existsSync(fullPath) ? fullPath : null;

Where I was able to determine that the expected path was not:

dist/__mocks__/@org/local-util/file.js

but

dist/@org/local-util/__mocks__/file.js

because the module was reported as not "external"