fuse-box/docs/development/launching.md

Fuse-Box a bundler that does it right

# Launching on server

You can capture an event when a single bundle is completed. You will have access to `FuseProcess` that will help you to launch your application on server.


```js

fuse.bundle("bundle2")
    .instructions(`~ index.ts`);
    .completed(proc => proc.start())

fuse.run()
```

## Executing a bundle


```js
completed(proc => proc.exec())
```

The following code will spawn a separate nodejs process once.

## Start / restart


```js
completed(proc => proc.start())
```

The following code will spawn a separate nodejs process, if a process is already running FuseBox will kill and spawn a  new one.

## Require

```js
completed(proc => proc.require(opts))
```

The following code will require a file in the same process as the fuse process instead of launching a new one.

The differences are :
* A bundle is executed in a `Promise` and its exports are available to the fuse caller : `proc.require().then(exports => void)`.
* A bundle has access to the same loaded libraries than the fuser, they share the same global object.
* A bundle is inspected if fuse is inspected: `node --debug fuse.js` debugs the bundle too.
* To free the allocated resources when a bundle is restarted, there is no clean `process.kill` option; it must therefore export a `close` function, or a default that has such a function.

An `express` bundle would look as follows:

```js
export default app.listen(process.env.PORT);
```

### Options
* `close(bundleExport)=> Promise`: A closing function.

The exports of the main file can be retrieved with `bundleExport.FuseBox.import(bundleExport.FuseBox.mainFile)`

### Closing function

When the module is unloaded, the first of these functions is called :
* A function `close(bundleExport)=> Promise` given as an option to `require`

After, if the bundle has a main file,

* An `export function close(): Promise` in the bundle
* A default export who has a `close()=> Promise` function.

If the close function returns a promise, this one will be awaited before requiring the new version of the bundle. If it returns anything else than a promise, the value is ignored.
The `require` function by itself returns a promise that resolves to the loaded bundle main-file `FuseBox` Object.