Why yarn don't use symlink?

[jefer94]

Do you want to request a feature or report a bug?

I request a feature.

What is the current behavior?

Yarn is good as package manager, but when I'd use yarn add something, it do a integrity test, check the checksums, check package.json and yarn.lock, and resolve de dependencies, for finally do a copy of the cache in node_packages, it's in development environment is unnecesary because only want add a dependencie for my project, this features are great for production environment.

Also in a Celeron with Google Chrome, with Yarn instaling dependencies, my machine is lag, ins't because of Google Chrome, the integrity check with the copy folder instead of used symlinks harms performance, I only want that if I forgot instaled a little dependency like express, do not have to wait for yarn to do all this again, if I forgot other little dependecy the time that i wait multiply by three, it's worrying.

If the current behavior is a bug, please provide the steps to reproduce.

Choco Algorithm

What is the expected behavior?

That yarn will have a development mode with symlinks, and a production mode.

Please mention your node.js, yarn and operating system version.

software	version(s)
Node	9.2.0
Yarn	1.3.2-20180102.1415
Operating System	Arch Linux x86_64

[jefer94]

If you're reproduce the error, create a .env file with

NODE_ENV=development

[swrobel]

See here: #499

[BYK]

To be able to install a deterministic tree, Yarn needs to calculate the whole tree even if you change a single dependency. This would be the same even if we used symlinks everywhere.

If you have a more concrete implementation in mind that wouldn't break our strong guarantees, feel free to submit an RFC here: https://github.com/yarnpkg/rfcs