gabrielcsapo / gabrielcsapo/node-git-server

Can not catch error when start listen

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Description

The JSDoc of the `Git.listen()` method states that "the function to call when server is started or error has occured" in the description of the `callback` argument.

https://github.com/gabrielcsapo/node-git-server/blob/5279f64b200b3d8e8f3d537c28c86793033e6285/lib/git.js#L429-L441

However, in reality, if the server fails to start with an error, the callback is not called.
In addition, **this error cannot be catched even with [try...catch statement](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/try...catch)**.

> The Server object is a Node.js EventEmitter. As with all EventEmitter's, _most_ errors are passed to the `'error'` event. If no handler is registered for the `'error'` event, those bubble up to be thrown. `try/catch` does not work because when listen is attempted, any errors that occur are caught and emitted on the `'error'` event using `process.nextTick()` -- that is, by the time the error is actually reported, the `try/catch` block has already exited. As a fallback, you can register an `'uncaughtException'` handler on `process` as a catch all for any unhandled errors that occur on any EventEmitter object, but it's best to simply set the `'error'` callback on the server object.
>
> _Originally posted by @jasnell in https://github.com/expressjs/express/issues/2856#issuecomment-172566787_

The best way to resolve this problem is to register the `error` event on [the `http.Server` object](https://nodejs.org/docs/latest-v6.x/api/http.html#http_class_http_server) to get the error.
Currently (version 0.6.1) we can get the error in the following ways:

```js
const Server = require('node-git-server');

const repos = new Server('path/to/tmp', {
autoCreate: true
});
const port = process.env.PORT || 7005;

// ...

repos.listen(port, () => {
console.log(`Success!`)
});
repos.server.on('error', error => {
console.error(`Error: ${error}`);
});
```

However, this solution requires the use of [the `server` property](https://github.com/gabrielcsapo/node-git-server/blob/5279f64b200b3d8e8f3d537c28c86793033e6285/lib/git.js#L449-L451) that are not in the documentation.
In addition, this method is not intuitive. The user cannot catch the error in the callback, nor in the try...catch statement. This solution requires knowledge of Node.js built-in http/https modules.

The ideal solution is a change that allows the function in the `callback` argument to catch the error.
To do this, this project needs to make the following changes to the `Git.listen()` method:

```diff
listen(port, options, callback) {
const self = this;
if(typeof options == 'function' || !options) {
callback = options;
options = { type: 'http' };
}
const createServer = options.type == 'http' ? http.createServer : https.createServer.bind(this, options);

this.server = createServer(function(req, res) {
self.handle(req, res);
});

+ this.server.on('error', callback);
+
this.server.listen(port, callback);
return this;
}
```

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