How symlinked node_modules structure helps to avoid circular symlinks?

[Peccansy]

I want to clarify for myself this statement from the FAQ:

Although pnpm uses linking to put dependencies into node_modules folders, circular symlinks are avoided because parent packages are placed into the same node_modules folder in which their dependencies are. So foo's dependencies are not in foo/node_modules, but foo is in node_modules together with its own dependencies."

Please, can somebody give an example of a problem? I think that I don't understand in which case a cycle might appear when we work with different structure :(

[zkochan]

A simple example would be: foo has bar in the dependencies and bar has foo in the dependencies. foo -> bar -> foo -> bar...

[zkochan]

if pnpm would write the node_modules of foo to foo/node_modules, we would get a circular symlink

foo/node_modules/bar -> ../../bar
bar/node_modules/foo -> ../../foo

but pnpm writes node_modules one level up

[email protected]/node_modules/bar -> ../../[email protected]/node_modules/bar
[email protected]/node_modules/foo -> ../../[email protected]/node_modules/foo

[zkochan]

related pages:

• https://pnpm.io/symlinked-node-modules-structure
• https://pnpm.io/blog/2020/05/27/flat-node-modules-is-not-the-only-way