Enable offline Yarn support

[gaearon]

It appears that it doesn't work. Shall we opt in?

[sylvainbannier]

I have issues with offline support in yarn v0.17.10 yarnpkg/yarn#2162. Waiting, for triage. If this is confirmed, then I guess CRA should wait for a fix in Yarn.

[gaearon]

Note that I also tried --offline and it didn't work because it requested latest whereas we only have a specific version in cache (for example 0.8.4). I wish there was a way to "agree" to use whatever local version we have if there is no network connection.

Related: yarnpkg/yarn#1277 (comment)

Possible improvement is to give user option [y/n]-prompt to use latest local version. (out of scope for this PR, should be feature request?)

[gaearon]

Filed as yarnpkg/yarn#2225.

[voxsim]

@gaearon please let me know if this works right now ;)

[gaearon]

Does it require any flags?

[voxsim]

@gaearon sorry for the late answer, but I lose some time to understand where I have to change the yarnpkg, to use what I build instead of the global package :)

Btw if you add --offline after --dev and --exact it should work from the next version!

[gaearon]

Want to send a PR?

[voxsim]

Sure

[gaearon]

Thx

[voxsim]

@gaearon I prefer to wait for the PR, because if you add --prefer-offline still don't work properly. I mean when you are online it does not switch from offline to online and other stuff, the road seems long I think you should reopen #2225. I will work on that because It could be useful for me creating react app offline ;)

Apart from this, do you think some end-to-end tests for create-react-app could be useful? Test manually the scripts every time is challenging :P