I have a project that uses Yarn 2 and I wanted to install a dependency directly from a GitLab (Lab not Hub) repo.

The doco lists all the supported protocols. There is GitHub specific support but also a general one for any git repo:

[email protected]:foo/bar.git

Trying this format gives me an error:

$ yarn add "[email protected]:ternandsparrow/strapi-initial-data.git"
➤ YN0000: ┌ Resolution step
➤ YN0001: │ Error: [email protected]:ternandsparrow/strapi-initial-data.git isn't supported by any available resolver
...

The HTTPS protocol isn’t listed on that page but it used to work with Yarn 1 so let’s try that:

$ yarn add https://gitlab.com/ternandsparrow/strapi-initial-data.git\#main
Internal Error: Invalid descriptor (https://gitlab.com/ternandsparrow/strapi-initial-data.git#main)
...

That’s a big fail.

Looking at the yarn add -h help page shows that you need a leading name fragment that seems to give the package a name:

...
Add a package from a GitHub repository (the master branch) to the current workspace using a URL
  $ yarn add lodash@https://github.com/lodash/lodash
...

The solution

Following that advice and redundantly adding that <name>@ prefix turns out to work, yay. This is the command that worked for me:

yarn add "strapi-initial-data@https://gitlab.com/ternandsparrow/strapi-initial-data.git#main"

Note: the default branch in this repo is main so I had to specify it as yarn still expected master.