updates to webpack4

[christopher-johnson]

closes #76

• also updates babel and eslint packages to work with new webpack4 api
• babel-preset-react-app includes both preset-env and preset-react (among others) as a bundle.
• mixing import and module.exports is no longer allowed in an ES6 module. (ref changes in index.js)
• includes required linting changes to pass build and tests. Most are react/destructuring-assignment
• adds "no-console": "off" rule to .eslintrc as console log statements are typical with node.
• adds paths.js which includes path resolvers and aliases for scripts.
• adds NODE_ENV to script defs in package.json.

[mejackreed]

Thanks @christopher-johnson ! This looks great to me. I really like how you list out the changes individually in the PR.

One quick question, should the development build (running npm start) get the development environment?

[mejackreed]

How does this work with the .eslintrc file which extends airbnb. Should that just be an array and specified there?

[christopher-johnson]

eslint will read both config from .eslintrc and the package.json. I agree that it would be cleaner to put that in the .eslintrc.

[mejackreed]

Gotcha. Do you mind making that small change here?

[christopher-johnson]

it turns out that eslint does not read the package.json if there is an .eslintrc. if it had, then eslint-config-react-app (as well as eslint-plugin-flowtype) would have been required as a dependencies. this is a useful extension for accessibility checks, so I do not think that there is a downside to adding it here. note, however, that it is entirely optional.

[christopher-johnson]

about the dev mode and dev server in the start script, this still needs some work. It is fairly typical to have a separate webpack config for development and the dev server, and this can be done in another PR.

currently, the start script has an extra NODE_ENV=development that does nothing in the initial build since it is overridden in the build script with a production mode, and this should be removed. But the watch script is set to the development environment. This should disable webpack from compiling production optimizations in concurrency.

[mejackreed]

Thanks for breaking this out @christopher-johnson. We reviewed this today in the POC session and appreciate your work on upgrading to webpack 4. We did see a few things that we would like to update, so will likely tackle that as a team in our pairing session.

Thanks again! 🥂