Custom cache directory should be resolved to an absolute path

[mojavelinux]

Expected Behavior

I expect nyc to consistently use the same cache directory throughout the process. When a custom cache directory is specified as a relative path, and the working directory of the process changes, this assumption is violated.

The custom cache path needs to be resolved to an absolute path (using path.resolve()) before it's used.

Observed Behavior

If a custom cache directory is specified as a relative path (such as in package.json), and the working directory of the process is changed by one of the tests, then the cache directory will be recreated in a new location for that portion of the test suite. This puts cache files in an unexpected location and defeats the purpose of having a cache.

If the cache directory is left unspecified, then nyc correctly resolves the value to an absolute path. It's the custom path that isn't being resolved.

See: https://github.com/istanbuljs/nyc/blob/master/index.js#L52

This line needs to be:

this.cacheDirectory = path.resolve(config.cacheDir) || findCacheDir({name: 'nyc', cwd: this.cwd})

Forensic Information

Operating System: Fedora 26 (Linux)
Environment Information:

Node: v8.9.3
npm: 5.5.1
yarn: 1.3.2
nyc: 11.4.1

[mojavelinux]

This is easily reproducible by simply changing the working directory of the process in a test:

describe('cache directory problem', () => {
  it('should put .nyc_cache in different folder', () => {
    process.chdir('another_folder')
    // require some code that nyc is going to cache
  })
})

Naturally, this only happens if the cache operation is triggered after the working directory change...so we're talking code which is loaded dynamically.

[bcoe]

@mojavelinux agreed, this sounds like a bug; any interest in submitting a failing test?

[mojavelinux]

Already did. Check the PR. #766.

[mojavelinux]

As a bonus, I added a test for both cases.

[mojavelinux]

I discovered this bug when my test suite started throwing errors trying to write the nyc cache files. Since the cache folder was moving, it was getting caught up in the clean up script that runs in the beforeEach of my suite. When nyc tried to write to the cache folder, it was gone.

[coreyfarrell]

Thanks for the fix, looks like this released in nyc@11.5.0. If I'm mistaken please let me know and I can reopen this issue.