Add template support

[mrmckeb]

This is a work in progress. Do not merge.

This has become a little more complicated than I first envisioned. Right now, I'm still working through the init part of this. The plan is as follows:

• react-scripts and create-react-app-template-* are installed as dependencies. Either or both of those can be defined via CLI.
  • Default is current default template.
  • Although the supported scripts version (range) is included in the template's peerDependencies, this is not used during install.
• Upon react-scripts init, the template is copied from template package, and peerDependencies are installed from that package (excluding the scripts-version). That package is then removed, as it no longer has any value.
  • When using non-standard scripts, or a scripts version that is below the peerDependencies of the template, appropriate warnings will be shown - but the user can still continue. This, importantly, allows custom scripts versions to work with the template.
  • Optionally, the scripts version range could be in engines... but that doesn't feel clean.

The typescript flag is deprecated under this process.

[mrmckeb]

OK, so I need to work on tests for this - and make sure it all works correctly - but the idea is in place.

The biggest issue I see with this implementation is that a) the template may require a different scripts version than the one the user set, and b) as the template is handled by react-scripts, we can only warn a user when scripts versions don't match - when perhaps we should just install the scripts package requested by the template.

[Ugzuzg]

Would be awesome to have the ability to add custom scripts to the package.json. Say, my template has internationalisation, and I want to add extraction script to the project.

[mrmckeb]

This can be tested with:

node ./create-react-app/packages/create-react-app test-project \
  --template file:./create-react-app/packages/create-react-app-template/ \
  --scripts-version file:./create-react-app/packages/react-scripts/

[nartoland]

Ok

[gc]

After cloning your branch, and running your exact command, I get this error:

error An unexpected error occurred: "https://registry.yarnpkg.com/create-react-app-template-file;./create-react-app/packages/create-react-app-template/: Reques
t \"https://registry.yarnpkg.com/create-react-app-template-file;./create-react-app/packages/create-react-app-template/\" returned a 405".
info If you think this is a bug, please open a bug report with the information provided in "C:\\Dev\\test-project\\yarn-error.log".

Aborting installation.
  yarnpkg add --exact react react-dom create-react-app-template-file;.\create-react-app\packages\create-react-app-template\ file;.\create-react-app\packages\re
act-scripts\ --cwd C:\Dev\test-project has failed.

Yarn v1.12.3
Node v11.6.0
OS win32 x64

EDIT: I tried debugging this but I'm not really sure whats wrong or causing it, a couple observations I made are:

• : is being changed into ; for some reason, I can manually .replace this to get past that issue
• it attempts to install file:./... for the template and scripts, if i remove the file: in this, it seems to get further without crashing.
• if that test cmd works fine for you, then perhaps its an issue with windows? assuming you're using linux/macOS

[mrmckeb]

I'm working on Ubuntu (WSL actually), but it may be an issue we need to look into.

That being said, the file:.. resolution` if for testing this PR and is actually passing through to npm/Yarn.

[Ugzuzg]

Any further work on this?

[mrmckeb]

Hi @Ugzuzg, this is a 3.2 goal now - I'll be restarting work on this next week.

We had some more urgent matters and wanted to think about this a little more.

Perhaps you can share a little more about what you'd like to see from templates?

[Ugzuzg]

Custom scripts, as mentioned above.

Also would be great to install additional dependencies. This PR achieves custom dependencies installing peerDependencies of a template, I believe? So this case is covered.
The ability to distinguish deps between dependencies and devDependencies isn't necessary, but is welcomed.

Thank you!