yarnrc: respect XDG_CONFIG_HOME setting

[kevinburke]

If a user has a XDG_CONFIG_HOME environment variable, read and write
the yarnrc file from XDG_CONFIG_HOME/.yarnrc, not from $HOME/.yarnrc.

The specification can be found here:
https://wiki.archlinux.org/index.php/XDG_Base_Directory_support

Fixes #2334.

[kevinburke]

One test failed when I ran them locally but it seems unrelated; I can add a separate issue for that if you like.

 FAIL  __tests__/commands/install/integration.js (224.941s)
  ● install should respect --no-bin-links flag

    Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL.

      at ontimeout (timers.js:380:14)
      at tryOnTimeout (timers.js:244:5)
      at Timer.listOnTimeout (timers.js:214:5)

[kevinburke]

Another option would be to remove the leading period if a user explicitly specifies a directory; the "hidden" nature of dotfiles was apparently an accident, see https://plus.google.com/101960720994009339267/posts/R58WgWwN9jp for more information.

[kevinburke]

I just rebased against master and I believe this is failing now because of an unrelated third-party dependency problem.

[arcanis]

Thanks! Two things:

• Could you also update the rc.js file (it's a new file, so you might need to pull)?
• You probably also want to update getPossibleConfigLocations (otherwise, unless I'm mistaken, you will write to XDG_CONFIG_HOME, but not read from it)

Don't forget than in both case we want to read both ~/.yarnrc and ~/$XDG_CONFIG_HOME/.yarnrc (possibly with ~/.yarnrc being the most trustable authority and overriding any config inside the xdg folder).

[jasonkarns]

This PR, while an improvement, does not bring yarn into compliance with XDG. The XDG spec defines a default value for XDG_CONFIG_HOME as ~/.config. This means XDG compliance would require ~/.config/yarn be used when XDG_CONFIG_HOME is not set.

Also, I would recommend not using a hidden file within the XDG location. Part of the reason for leveraging XDG is to not require the files be hidden individually. I would suggest:

$XDG_CONFIG_HOME/yarn or more conventionally: $XDG_CONFIG_HOME/yarn/config

It is obvious by the xdg-config location that the files contained therein are configuration files. Thus the "rc" suffix is redundant. And it seems to be conventional for xdg-compliant tools to create a self-named directory under the config directory in which to place all their files, thus allowing for additional files in the future.

[jasonkarns]

@kevinburke why closed? I very much want to see xdg support in yarn (raised my concerns above not to dissuade this PR but hopefully just tweak it a bit to be more spec compliant)

[felixsanz]

@kevinburke friendly ping!

[riri]

I'm a new yarn user, and I was happy to see the cache goes in $XDG_CACHE_HOME, but smiled when seeing the .yarnrc. @jasonkarns is right in his analysis, and the way it should go is rather simple finally:

• if $XDG_CONFIG_HOME is set, use (and write to) $XDG_CONFIG_HOME/yarn/config
• else if $HOME/.config exists, use $HOME/.config/yarn/config
• else as a fallback, use $HOME/.yarnrc

[kevinburke]

I don't have time to work on this, and there are enough different ideas about how this should be implemented, feel free to add your own patch