(p)npm manages both fine with the dependency directory structure.

This is literally not possible.

If you have local dependency repo and dependency manifest, during the build, you can either:

1. Check if local repo is in sync - correct build, takes more time

2. Skip the check - risky build, but fast

If the dependencies are only in the cache directory, you can have both - correct and fast builds.

I don't follow. In pnpm there's a global cache at ~/.pnpm with versioned packages and node_modules has symlinks to those. Dependencies are defined in package.json transitive dependencies are versioned and SHA512-hashed in pnpm-lock.yaml.

E.g.

  $ ls -l ./node_modules/better-sqlite3
  ... node_modules/better-sqlite3 -> .pnpm/[email protected]/node_modules/better-sqlite3

You still need to have those symlinks checked. For example you switch branch to one with updated package.json, now you need either to check symlinks or you risk to have incorrect build.

Introducing a directory that needs to stay in sync with dependency manifest will always lead to such problems. It is good that Python developers do not want to repeat such mistake.

Just run `pnpm install` after switching the branch. Or add `pnpm install` into the build step. And many build tools will do that automatically. If the deps are in sync with the manifest, that takes typically less than a second.

This is a problem I've never encountered in practice. And it's not like you don't have to update the dependencies in Python if they are different per-branch.

The thing is you don't need to do this in "normal" system where dependencies are stored in local cache and build tool is using them during the tasks.

If JS had a proper build tool then creating such directory inside project would not be needed. Instead in JS world you have only dependency downloader with some crude script runner.