Hey! Thanks for tackling this. I think we wouldn't want to apply this as a pre-processing pass, otherwise it opens the door to pretty weird things if the environment variables contain things that could lead to valid YAML.

What do you think of instead doing this replacement within interpretValue, right here:
https://github.com/yarnpkg/berry/blob/master/packages/yarnpkg-core/sources/Configuration.ts#L434

Hmm, didn't see it. Will dig into it.
Btw, is there a way to run yarn with node --inspect flag?

easiest way is YARN_IGNORE_PATH=1 node --inspect-brk ./scripts/run-yarn.js

@arcanis I moved replacement into interpretValue, refactored replacement to .replace method, added tests and documented this.

Not sure about tests: maybe we should separate it and check all cases in packages/yarnpkg-parsers/tests/syml.test.js and in packages/yarnpkg-core/tests/Configuration.test.ts just check that replacement works?

Also there is something strange with the test on win.

Perfect! Thanks @7rulnik! 😃

Could we have some way to simply disable this functionality all together maybe via .yarnrc.yml or via an environment variable?

Please open an issue with a repro. This PR is about the configuration, whereas you're talking about scripts 🙂

@yinzara Not sure what cross-env has to do with the feature introduced in this PR. This PR adds support for environment variables inside the configuration (.yarnrc.yml), so that the following can work:

npmRegistries:
  "//registry.npmjs.org":
    "npmAuthToken": ${MY_AUTH_TOKEN}

I believe you're referring to the environment variables inside our portable shell, which go through a completely different parser that correctly handles nested environment variables and a lot of other things. The portable shell has support for many features that work across all environments (including on Windows), like environment variables, command chains, subshells, some builtins.

For your use case, you can:

• cross-env 'echo $PWD' - quote what needs to be passed to cross-env so that our shell doesn't expand it
• echo $(pwd) - use a subshell and the pwd builtin which works across all environments

Edit: @arcanis responded faster than me. 😄

THANKS! That's good enough! I appreciate it.

I guess we can also add support for the $PWD environment variable for better compliance with bash, even though we'd introduce 2 ways to do the same thing (echo $(pwd) and echo $PWD). @arcanis What do you think?

Edit: I realize that the discussion shouldn't continue here, my bad. 🤦

I'll open another issue specifically to add $PWD resolution so it's bash compatible. I think that's an important thing.