Better support for monorepos

bug report

On a lerna-based monorepo, there are some issues with patch-package.

Suppose I have this folder structure...

.
├── ...
├── packages
│   ├── a
│     └── patches
│     └── package.json
├── node_modules
└── package.json

... and suppose I put patch-package dependency in the package a together with a postinstall script.

Current Behavior

The package a should work in isolation from the top-level folder and other packages.

• When I do a npm i on the top-level folder, it will install dependencies and so do a npm i on a (if things are well configured). But probably it will hoist dependencies of a in the top-level node_modules instead of a local one (ie. instead of a node_modules inside the a folder).
• So patch-package will be executed and tries to patch things in a/node_modules but since dependencies are hoisted in the top-level folder, it will fail (if no symlink are present).

Possible Solution

Add a flag to enable patching of the top-level node_modules. ie:

• it's very easy to find the root folder, just do a find-up for a package.json that contains a workspaces field and/or a lerna.json file.
• From there, if you can't patch the local node_modules folder (ie. for instance it doesn't exist) tries to patch the root node_modules (when flag is enabled)

Context

• I have a monorepo and I really don't want to put the patches in the root folder, but rather in the packages, so patch-package can work for packages individually.
• Also in my setup there are no local node_modules ie. no node_modules in packages/a and I would like patch-package to work out-of-the-box for this kind of situation (with a flag if it's ok).
• I don't want to patch patch-package

Your Environment