Combined coverage CI issue: nyc merge reports yields an empty coverage.json file in CI

[muratkeremozcan]

3-way combined coverage is working really well locally (CyE2e + CyCT + Jest)

Local reproduction:

git clone https://github.com/muratkeremozcan/react-hooks-in-action-with-cypress.git
cd  react-hooks-in-action-with-cypress
yarn install

I shared the .env file env vars in the Discord DX chat, you can use that or for now disable the Percy, Applitools, and FeatureFlag tests. The only variance here will be lower coverage for e2e tests.

Run the component & e2e tests in any order, the coverage combines out of the box in coverage-cy folder:

yarn cy:run-ct
yarn cy:run-e2e

Run the Jest test:

yarn test

Combine the coverage into combined-coverage folder:

yarn cov:combined

Problem: nyc merge creates an empty coverage.json file when merging Cypress coverage results in CI.

The CI repeats the local workflow, in a more imperative way, and outputs it step by step.

Downloading the artifacts to a local folder and running the nyc merge command works perfectly fine. The issue is doing the same in CI.

Step by step CI output

video demo and issue reproduction

Are you aware of any workarounds? Can you spot any mistakes? Please let me know.
If this does not work, the only way forward with combined coverage in CI is by using the the codeCov service, which is the next item in this PR.