Probably an oversight but currently env preset's `modules` option always evaluates to 'auto'. We probably want it to be set to false, especially in prod, to have Webpack handle modules natively.
## Minor changes
When `NODE_ENV=test` is used we'll now apply the `'auto'` configuration for modules transformation. Which causes Babel to check if the current environment needs to be transformed or not. In practice this means that the following `.babelrc` is not needed anymore:
**OLD**:
```json
{
"env": {
"development": {
"presets": ["next/babel"]
},
"production": {
"presets": ["next/babel"]
},
"test": {
"presets": [["next/babel", { "preset-env": { "modules": "commonjs" } }]]
}
}
}
```
**NEW**:
```
{
"presets": ["next/babel"]
}
```
## Patches
`@babel/preset-react` has a `development` option that automatically applies a development-time plugin we manually applied before (`@babel/plugin-transform-react-jsx-source`). It also adds another development-time plugin that is said to make debugging/errors clearer: `@babel/plugin-transform-react-jsx-self` which we didn't apply before. Overall this means we can take advantage of preset-react to provide these plugins.
Fixes#4691Fixes#4614
This PR gives path to https://github.com/zeit/next-plugins/pull/242
I did not add or remove `^` near dependency versions in package.json files. However, I don't exclude that some changes can be made given that rc is more stable than beta.
The prepares for next-server.
I also took this as an opportunity to get all build directory paths from a single location, as they were previously scattered across webpack/babel plugins and loaders.
