Modularise scripts

[djgrant]

Following the discussion and for reasons mentioned in #1431, this PR aims to refactor the webpack abstractions found in the start script out into their own utility modules.

I've aimed to maintain the general narrative of the script by keeping the running of methods in the script and using callback to eliminate interweaving.

Summary of changes

/config
  + webpackDevServer.config.js
/scripts
  /utils
     + addWebpackMiddleware.js
     ~ createJestConfig.js
     + createWebpackCompiler.js
  ~ eject.js
  ~ start.js 

• All files found in specified folders get copied to the app directory on eject
• Except files flagged with a // @remove-file-on-eject comment, which will be skipped i.e. scripts/eject.js & scripts/utils/createJestConfig.js

[djgrant]

@gaearon Thinking that the dev server config could just be moved to config/ instead.

[gaearon]

This currently breaks CI after ejecting: https://travis-ci.org/facebookincubator/create-react-app/jobs/194654920

I think you might need to add more files to the copying script in scripts/eject.js.

[djgrant]

I've introduced a convention of adding // @remove-file-on-eject to the top of files that are not to be copied over at ejection. This removes the need for a whitelist of files and allows me to put the utils folder inside of scripts where it can be used in an ejected app.

[gaearon]

This looks pretty good. I'm sorry we missed it.
Can you please rebase this with latest changes?

[djgrant]

@gaearon no worries. Now rebased.

[Timer]

Is this functionally equivalent? If so, this looks great -- I feel like this is something we need to have rebased and just merged immediately to prevent merge issues one after another.

My only concern is if this works with our recently-added support of linking react-scripts; but that's something I'd be willing to test after getting this in. Only reason I asked is because of the new method of getting files to eject.

@gaearon, if this is rebased again can we merge immediately? I don't foresee any more script changes we're making in the 0.9.x branch.

[gaearon]

I'm fine with merging now but let's make sure we don't lose any recent changes accidentally.

That is, the reviewer needs to actually read through those functions and make sure the contents match.

[Timer]

I'll review this.

[Timer]

Should be good, @gaearon -- I believe I captured all the missing changes in 38bc01c.

[gaearon]

It is confusing that we only call it when showInstructions is true.
We should instead pass it as an argument.

[gaearon]

Looks good aside from one nit.

[Timer]

Before:

Copying files into /Users/joe/Desktop/test2
  Adding config/env.js to the project
  Adding config/paths.js to the project
  Adding config/polyfills.js to the project
  Adding config/webpack.config.dev.js to the project
  Adding config/webpack.config.prod.js to the project
  Adding config/jest/cssTransform.js to the project
  Adding config/jest/fileTransform.js to the project
  Adding scripts/build.js to the project
  Adding scripts/start.js to the project
  Adding scripts/test.js to the project

After:

Copying files into /Users/joe/Desktop/test1
  Adding /config/env.js to the project
  Adding /config/paths.js to the project
  Adding /config/polyfills.js to the project
  Adding /config/webpack.config.dev.js to the project
  Adding /config/webpack.config.prod.js to the project
  Adding /config/webpackDevServer.config.js to the project
  Adding /config/jest/babelTransform.js to the project
  Adding /config/jest/cssTransform.js to the project
  Adding /config/jest/fileTransform.js to the project
  Adding /scripts/build.js to the project
  Adding /scripts/start.js to the project
  Adding /scripts/test.js to the project
  Adding /scripts/utils/addWebpackMiddleware.js to the project
  Adding /scripts/utils/createWebpackCompiler.js to the project

Looks like we accidentally included /config/jest/babelTransform.js. Removed in 61e99ee.

[Timer]

Thanks so much for this, @djgrant! Your efforts will help many people who maintain forks of create-react-app. 😄

I hope I didn't upset you by making a few changes, we really wanted to get this in so we stopped breaking it every few days.

Merging once CI is green.

[Timer]

AppVeyor CI green on my repo.

[djgrant]

Smashing, great to see this in master! Thanks @Timer and @gaearon for ironing it out!

[tuchk4]

@Timer btw. Is there is any code convention (besides of eslint)? Use normal function or arrow?
Right now there are both normal and arrow are using. For example - eject.js.

[Timer]

We used to have a lower node requirement than Node 4, iirc. I'm not sure on an official preference.

[gaearon]

Arrows are fine. If it runs on Node 4 then it's good. But only in react-scripts.

Global CLI should stay parseable by Node 0.12 so that we can show a nice error message instead of crashing. (We could also split modern code into a lazy require.)