Alias solution for craco or rewired create-react-app

This is more than simple alias. This is also a multi-project src
directory. Currently, create-react-app (CRA) does not support more than one
src directory in the project. Monorepo, multi-repo and library projects with
examples require more than one directory like src.

This is merely an alias and multi-source solution for CRA
and this is not a replacement for multi-package management tools like
Lerna.

This requires to modify the CRA webpack configuration in runtime
(without ejecting) and works with one of:
* react-app-rewired
* customize-cra
* craco (see Using craco below)


#### This allows:

* quality and secure exports from outside src
* absolute imports
* any ./directory at root outside of src with Babel and CRA features

#### This is designed for:

* monorepo projects
* multi-repo projects
* library projects with examples

#### Advantages over other solutions:

* provided fully functional aliases and allows the use of Babel, JSX, etc.
outside of src (outside of project root may be enbled with special way
see the section below)

* provided fully secure aliases and uses the same module scope plugin from
the original create-react-app package for modules (instead of removing it),
to minimize the probability of including unwanted code

#### Installation

``sh
yarn add --dev react-app-rewire-alias
`

or

`sh
npm install --save-dev react-app-rewire-alias
`

$3

By default folders for alias may be near to src folder or in it.
Outside of project root is enabled with special way, see below.

Usage steps:

enumerate aliases in jsconfig.paths.json or tsconfig.paths.json*
include it in jsconfig.json or tsconfig.json*
enable your favorite any of react-app-rewired or craco*
apply this package plugin in config of react-app-rewired or craco*

#### Enumerate aliases in jsconfig.paths.json or tsconfig.paths.json

Create a separate file jsconfig.paths.json or tsconfig.paths.json, like this:

`js
// jsconfig.paths.json or tsconfig.paths.json
{
"compilerOptions": {
"baseUrl": ".",
"paths": {
"example/": ["example/src/"],
"@library/": ["library/src/"]
}
}
}
`

#### Add extends section to jsconfig.json or tsconfig.json

The paths section must not be configured directly in jsconfig.json
or tsconfig.json, but in a separate extends file mentioned above.
Now include this file in extends section, like this:

`js
// jsconfig.json or tsconfig.json
{
"extends": "./jsconfig.paths.json", // or "./tsconfig.paths.json"
"compilerOptions": {
// ...
}
}
`

$3

`js
// config-overrides.js
const {alias, configPaths} = require('react-app-rewire-alias')

const aliasMap = configPaths('./tsconfig.paths.json') // or jsconfig.paths.json

module.exports = alias(aliasMap)
module.exports.jest = aliasJest(aliasMap)
`

aliasMap may be filled manually, for non-typescript only, see api

$3

`js
// craco.config.js

const {CracoAliasPlugin, configPaths} = require('react-app-rewire-alias')

const aliasMap = configPaths('./tsconfig.paths.json') // or jsconfig.paths.json

module.exports = {
plugins: [
{
plugin: CracoAliasPlugin,
options: {alias: aliasMap}
}
]
}
`

aliasMap may be filled manually, for non-typescript only, see api


#### Enable react-app-rewired

Integrating react-app-rewired into your project is simple
(see its documentation):
Create config-overrides.js mentioned above, in the project's root directory
(the same including the package.json and src directory).
Install react-app-rewired

`sh
yarn add --dev react-app-rewired
- or -
npm install --save-dev react-app-rewired
`
and rewrite the package.json like this:

`diff
"scripts": {
- "start": "react-scripts start",
+ "start": "react-app-rewired start",
+ ... // same way
}
`

#### Enable craco

According to craco
docs install craco:

`sh
yarn add --dev craco
- or -
npm install --save-dev craco
`

and replace react-scripts in package.json:

`diff
"scripts": {
- "start": "react-scripts start",
+ "start": "craco start",
+ ... // same way
}
`

#### API

* alias(aliasMap)(webpackConfig)

The function alias() accepts aliases declared in form:

`js
const aliasMap = {
example: 'example/src',
'@library': 'library/src',
}

module.exports = alias(aliasMap)
`

To make all things worked, aliases must be declared in jsconfig.json or tsconfig.json.
However, it must be declared in a separate extends file (see section Workaround for
"aliased imports are not supported" below)

The result is a function which will modify Wepack config

* configPaths()

The function configPaths() loads paths from file compatible with jsconfig.json
or tsconfig.json and returns path in form acceptable for alias() function.
The tsconfig.json is prioritized over the jsconfig.json in the loading sequence.

`js
const aliasMap = configPaths('./tsconfig.paths.json')

module.exports = alias(aliasMap)
`

* extendability

As any react-app-rewire or customize-cra rewire extension this can be integrated
with another:

`js
module.exports = function override(config) {
const modifiedConfig = alias(...)(config)
...
return someElse(modifiedConfig)
}
module.exports.jest = function override(config) {
const modifiedConfig = aliasJest(...)(config)
...
return modifiedConfig
}
`

#### Workaround for "aliased imports are not supported"

CRA overwrites
your tsconfig.json at runtime and removes paths from the tsconfig.json,
which is not officially supported, with this message:

> `
> The following changes are being made to your tsconfig.json file:
> - compilerOptions.paths must not be set (aliased imports are not supported)
> `

The suggested workaround
is to move the paths to a different .json file, e.g. tsconfig.paths.json, like this:

`json
/ tsconfig.paths.json /
{
"compilerOptions": {
"baseUrl": ".",
"paths": {
"example/": ["example/src/"],
"@library/": ["library/src/"]
}
}
}
`

with that file's subsequent inclusion in the tsconfig.json using extends:

`json
/ tsconfig.json /
{
"extends": "./tsconfig.paths.json"
}
`

Outside of root

Alias folders outside of the root of the project currently fully functional and
works fine but are not recommended. It has more complicated implementation which
currently named dangerous and exported from package separately. Due to complicity
it has a higher probability of being incompatible with the next release of
create-react-app until an update is released, since these are different systems.
However same is for the base implementation but with less probability of being
incompatibe with next cra release.

It provides aliases with the same feature set as the original create-react-app.
create-react-app does not support aliases and additional src-like directories as
it does not supports aliases outside of the root project directory.

Aliases outside or project root directory may be implemented with some
limitation
of feature set. That is solved by disabling ESLint checking.

This implementation is moved to separated code set named aliasDangerous to be not confused
with alias. To use it just replace import like this:

`diff
- const {alias, configPaths, CracoAliasPlugin} = require('react-app-rewire-alias')
+ const {aliasDangerous, configPaths, CracoAliasPlugin} = require('react-app-rewire-alias/lib/aliasDangerous')
`

And replace alias with aliasDangerous:

`js
module.exports = function override(config) {
aliasDangerous({
...configPaths('tsconfig.paths.json')
})(config)

return config
}
`

Tips

* keep only one node_modules directory

Confusions in deps versions may bring unclear errors or problems. For example, an application
is not working without any error. Or another example is error in react-router -
component do not see when actually code is correct and it falls with:

> should not use Route or withRouter() outside a Router

This may be a result of some confusion in node_modules folders for multi-repo projects.
Same take place in plain create-react-app if somehow one or more additional
node_modulest directories appear in src.

To avoid this problem use only one main project node_modules directory.

* keep away from working with nested project

Default bundler configuration doesn't assume your configuration and may mix deps from
node_modules from different projects (top project and nested project) so this may
bring mentioned above confusions with deps versions. To avoid problems:
**do not install and run within nested project directly when it is nested or integrated
in another one - but only independent top level configuration** Or consider to eject
or configure Webpack manually.

* do not relay to deps versions synchronization

Some libraries use instanceof and other type comparisions. For example , two objects
created with the same params in the same code of the same library version but installed in
different node_modules and bundled separately - will mostly have the same data and same
behaviour but different instance type. Such libraries will be unable to recognize their own
objects and will lead to unpredictable behaviour. So **use only one main project
node_modules` directory**.