[Working as intended] relative paths inside protocols inside packageExtensions are resolved relative to the parent package's location

[goszczynskip]

Describe the bug

Patching fails with: ENOENT: no such file or directory, open './foo.patch' when trying to install with nodeLinker: "node-modules" set.

To Reproduce

Repo with example: https://github.com/goszczynskip/yarn-berry-bug-patch

Steps that I made:

• created yarn repo
• set nodeLinker to node-modules EDIT: with pnp it fails too
• patched watchpack from webpack
• add webpack to dependencies
• run yarn

Environment if relevant (please complete the following information):

• OS: Windows 10
• Node version v13.2.0
• Yarn version 2.0.0-rc.31 and sources

[paul-soporan]

(Thanks to @arcanis for explaining this to me first. 😄)

The current behavior is intended. This is kind of an edge case that affects all of the protocols that accept paths (patch:, file:, portal: etc.).

Dependencies declared through the packageExtensions field simply replace a package's dependencies, so relative paths are resolved relative to the path of the original package (in this case the root of the zip archive containing the package).
On the other hand, if the resolutions field contains dependencies with protocols with relative paths, they will be resolved relative to the project (your project's) root.

In short:

• The resolutions field should be used to override dependencies already declared (i.e. to apply your custom fixes).
• The packageExtensions field should be used to add undeclared dependencies.

I'll add a note about this in the description of the resolutions field.