The previous signature was not compatible with EventEmitter.emit(). The typescript compilation threw:
```
node_modules/socket.io/dist/namespace.d.ts(89,5): error TS2416: Property 'emit' in type 'Namespace' is not assignable to the same property in base type 'EventEmitter'.
Type '(ev: string, ...args: any[]) => Namespace' is not assignable to type '(event: string | symbol, ...args: any[]) => boolean'.
Type 'Namespace' is not assignable to type 'boolean'.
node_modules/socket.io/dist/socket.d.ts(84,5): error TS2416: Property 'emit' in type 'Socket' is not assignable to the same property in base type 'EventEmitter'.
Type '(ev: string, ...args: any[]) => this' is not assignable to type '(event: string | symbol, ...args: any[]) => boolean'.
Type 'this' is not assignable to type 'boolean'.
Type 'Socket' is not assignable to type 'boolean'.
```
Note: the emit calls cannot be chained anymore:
```js
socket.emit("hello").emit("world"); // will not work anymore
```
This commit restores the ability to send additional data in the
middleware functions, which was removed during the rewrite to
Typescript ([1]).
The only difference with the previous implementation is that the client
will now emit a "connect_error" (previously, "error") event with an
actual Error object, with both the message and an optional "data"
attribute.
```js
// server-side
io.use((socket, next) => {
const err = new Error("not authorized");
err.data = { content: "Please retry later" };
next(err);
});
// client-side
socket.on("connect_error", err => {
console.log(err.message); // not authorized
console.log(err.data.content); // Please retry later
});
```
[1]: a5581a9789
Both the "connected" and the "_sockets" maps were used to track the
Socket instances in the namespace.
Let's merge them into "sockets". It's a breaking change, but:
- the "sockets" object did already exist in Socket.IO v2 (and appears in some examples/tutorials)
- "sockets" makes more sense than "connected" in my opinion
- there was already a breaking change regarding the "connected" property (from object to Map)
Breaking change: the "connected" map is renamed to "sockets"
In previous versions, a client was always connected to the default
namespace, even if it requested access to another namespace.
This meant that the middlewares registered for the default namespace
were triggered in any case, which is a surprising behavior for end
users.
This also meant that the query option of the Socket on the client-side
was not sent in the Socket.IO CONNECT packet for the default namespace:
```js
// default namespace: query sent in the query params
const socket = io({
query: {
abc: "def"
}
});
// another namespace: query sent in the query params + the CONNECT packet
const socket = io("/admin", {
query: {
abc: "def"
}
});
```
The client will now send a CONNECT packet in any case, and the query
option of the Socket is renamed to "auth", in order to make a clear
distinction with the query option of the Manager (included in the query
parameters of the HTTP requests).
```js
// server-side
io.use((socket, next) => {
// not triggered anymore
});
io.of("/admin").use((socket, next => {
// triggered
console.log(socket.handshake.query.abc); // "def"
console.log(socket.handshake.auth.abc); // "123"
});
// client-side
const socket = io("/admin", {
query: {
abc: "def"
},
auth: {
abc: "123"
}
});
```
