[Feature]: support for interop default

[tmkx]

What problem does this feature solve?

Rstest enabled the esm format by default in #763 from v0.7.9, causing some test cases that rely on cjs interop to fail.

Is there a plan to support interpreting cjs module's default as named exports?

https://vitest.dev/config/deps.html#deps-interopdefault

What does the proposed API look like?

https://vitest.dev/config/#deps-interopdefault

[9aoy]

We will think about ways to support or avoid it in the future.

For now, the recommended approach is to explicitly configure the loading mode of the affected packages as CommonJS. This avoids relying on CJS default-to-named interop behavior, which is inherently ambiguous and can lead to inconsistent results.

import { defineConfig } from '@rstest/core';

export default defineConfig({
  output: {
    externals: {
      lodash: 'commonjs lodash', // externalize lodash as a CommonJS module
    },
  },
});

[tmkx]

library authors should be aware of this behavioral difference, but for application developers, this might lead to confusion imho.