hashFiles function throwing error.

We are facing issue with node caching today on ubuntu-18.04. Following is the error

 hashFiles('../../**/package-lock.json') failed. Fail to hash files under directory

This has been working for the past 2 years. However starting today morning we are facing this issue

   uses: actions/cache@v1
        with:
          path: ~/.npm
          key: ${{ runner.os }}-node-cache-${{ hashFiles('../../**/package-lock.json')}}
          restore-keys: |
            ${{ runner.os }}-node-cache-

24 hours back it was running as expected

[mbg]

We also started running into this issue today. After enabling step debug logging, it seems that for us the error was caused by a permissions issue. Specifically, during the CI run, a folder was created by Docker within the workspace with permissions that meant that hashFiles could not search that folder for files which matched our search pattern. I assume that this failed silently before, but is now an error due to https://github.com/actions/runner/pull/1678.

We are able to resolve this either by making the pattern more concrete (e.g. instead of using **/*.cabal, we could use **/foo.cabal, but then we need to be careful about adding all package files explicitly now and in the future) or by moving the folder created by Docker outside the workspace.

In any case, I am wondering though if the solution implemented by https://github.com/actions/runner/pull/1678 could be improved. At least, it would be nice to have a better indication of what the error is without having to enable step debug logging. Perhaps the errors should be warnings instead? Or perhaps there should only be an error if hashFiles returns an empty string?

[math0ne]

I resolved this by changing this:

      - uses: actions/cache@v2
        with:
          path: '**/node_modules'
          key: ${{ runner.os }}-modules-${{ hashFiles('**/yarn.lock') }}

to this:

      - uses: actions/cache@v2
        with:
          path: '/node_modules'
          key: ${{ runner.os }}-modules-${{ hashFiles('/yarn.lock') }}