[Bug] patch-commit does not return any output/error

• I’d be willing to implement a fix

Describe the bug

Running yarn patch-commit /path/to/generated/dir returns without output nor does it generate any file.

To Reproduce

yarn init --yes
yarn add slate-react
yarn patch slate-react
# make some changes to the package in the output directory
yarn patch-commit $dir

This returns no output. For some reason, it does not reproduce in sherlock (Sherlock gives output), but I can consistently reproduce locally.

Tried latest version and built from master. Tried Node 12, 14 and 15.

Reproduction

const {writeFile} = require('fs').promises
await writeFile(`./.yarnrc.yml`, 'nodeLinker: node-modules')

await yarn(`init`, `--yes`);

await yarn(`add`, `slate-react`);

const output1 = await yarn(`patch`, `slate-react`);
const [, line] = output1.split('\n')
const [, dir] = line.split('folder: ')

await writeFile(`${dir}/dist/index.es.js`, '// some changes')

const output2 = await yarn(`patch-commit`, dir);
expect(output2).not.toBe('')

Screenshots

Environment if relevant (please complete the following information):

• OS: OSX 10.15.7 [e.g. OSX, Linux, Windows, …]
• Node version: Tried Node 12, 14 and 15. [e.g. 8.15.0, 10.15.1, …]
• Yarn version: Tried latest and from master [e.g. 2.4.0, …]

Additional context

As an aside, the output from the command that sherlock gives is not consistent with the documentation, which states:

This will turn the folder passed in parameter into a patchfile

It actually doesn’t generate a patchfile, but outputs it into stdout.

[arcanis]

Perhaps it would be better to generate the diff in JS or not depend on git to do it since it may vary from OS to OS?

Oh interesting - I think it’s better to keep using git (generating patchfiles is very tricky, especially if it needs to be done fast), but we certainly can return a proper error message (we can even detect the flag support using stderr and explain how to fix it, for example via Please install git via brew etc).

Regarding your initial issue, the documentation is indeed unclear, but the current behavior is intended: Yarn is expected to generate the output but not the file. You can then redirect it to wherever you want. We purposefully don’t make assumptions regarding the filesystem at the moment. It’s often mentioned as something we can improve though, so I’d be open to hear about what we could do better.

[niieani]

Funny thing is, I had git installed via brew, it’s just that it wasn’t set as the first one in PATH. Running brew link --overwrite git fixed it. I’ve clarified the message and force-pushed the update to the linked PR. It doesn’t specify brew, but should be enough to understand what is the culprit.