WebSocket API change to make room for other connection options (SSL pinning)

Summary:
This is a simple groundwork PR to allow options to be passed to the `WebSocket` constructor. It represents a minor change to an undocumented part of the API, moving `headers` to within `options`.

This will be a BC for anyone manually specifying headers other than `origin` but a) that's not a common use case with WebSockets and b) it's not documented even in code and wouldn't currently pass a flow check.

NB: The third argument to the WebSocket constructor isn't part of the W3C spec, so I think this is a good place for RN-specific named parameters, better than adding a fourth argument. `protocols` needs to stay where it is, in line with the spec.

If this goes through I'd like to build on it by adding an additional connection option for SSL certificate pinning, as already supported by the underlying `okhttp` and `RCTSRWebSocket`. It could later be expanded for various other uses.

Currently, there's no way for a `WebSocket` user to specify any connection options other than url, protocol and headers. The fact that `WebSocket` connects in its constructor means any options have to go in there.

Connect to a websocket server using iOS and Android, observe the connection headers:
1. Without specifying `origin`, the default header should be set
2. Specifying it in the old way `new WebSocket(url, protocols, { origin: 'customorigin.com' })`
3. Specifying it in the new way `new WebSocket(url, protocols, { headers: { origin: 'customorigin.com' }})`.

I've tested myself using the test app with iOS and Android.
Closes https://github.com/facebook/react-native/pull/15334

Differential Revision: D5601675

Pulled By: javache

fbshipit-source-id: 5959d03a3e1d269b2c6775f3e0cf071ff08617bf

Libraries/WebSocket/RCTWebSocketModule.m

@@ -61,7 +61,7 @@ RCT_EXPORT_MODULE()
   }
 }
 
-RCT_EXPORT_METHOD(connect:(NSURL *)URL protocols:(NSArray *)protocols headers:(NSDictionary *)headers socketID:(nonnull NSNumber *)socketID)
+RCT_EXPORT_METHOD(connect:(NSURL *)URL protocols:(NSArray *)protocols options:(NSDictionary *)options socketID:(nonnull NSNumber *)socketID)
 {
   NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];
 
@@ -78,7 +78,7 @@ RCT_EXPORT_METHOD(connect:(NSURL *)URL protocols:(NSArray *)protocols headers:(N
   request.allHTTPHeaderFields = [NSHTTPCookie requestHeaderFieldsWithCookies:cookies];
 
   // Load supplied headers
-  [headers enumerateKeysAndObjectsUsingBlock:^(NSString *key, id value, BOOL *stop) {
+  [options[@"headers"] enumerateKeysAndObjectsUsingBlock:^(NSString *key, id value, BOOL *stop) {
     [request addValue:[RCTConvert NSString:value] forHTTPHeaderField:key];
   }];
 

Libraries/WebSocket/WebSocket.js

@@ -93,12 +93,27 @@ class WebSocket extends EventTarget(...WEBSOCKET_EVENTS) {
   // `WebSocket.isAvailable` will return `false`, and WebSocket constructor will throw an error
   static isAvailable: boolean = !!WebSocketModule;
 
-  constructor(url: string, protocols: ?string | ?Array<string>, options: ?{origin?: string}) {
+  constructor(url: string, protocols: ?string | ?Array<string>, options: ?{headers?: {origin?: string}}) {
     super();
     if (typeof protocols === 'string') {
       protocols = [protocols];
     }
 
+    const {headers = {}, ...unrecognized} = options || {};
+
+    // Preserve deprecated backwards compatibility for the 'origin' option
+    if (unrecognized && typeof unrecognized.origin === 'string') {
+      console.warn('Specifying `origin` as a WebSocket connection option is deprecated. Include it under `headers` instead.');
+      headers.origin = unrecognized.origin;
+      delete unrecognized.origin;
+    }
+
+    // Warn about and discard anything else
+    if (Object.keys(unrecognized).length > 0) {
+      console.warn('Unrecognized WebSocket connection option(s) `' + Object.keys(unrecognized).join('`, `') + '`. '
+        + 'Did you mean to put these under `headers`?');
+    }
+
     if (!Array.isArray(protocols)) {
       protocols = null;
     }
@@ -111,7 +126,7 @@ class WebSocket extends EventTarget(...WEBSOCKET_EVENTS) {
     this._eventEmitter = new NativeEventEmitter(WebSocketModule);
     this._socketId = nextWebSocketId++;
     this._registerEvents();
-    WebSocketModule.connect(url, protocols, options, this._socketId);
+    WebSocketModule.connect(url, protocols, { headers }, this._socketId);
   }
 
   get binaryType(): ?BinaryType {

ReactAndroid/src/main/java/com/facebook/react/modules/websocket/WebSocketModule.java

@@ -83,7 +83,7 @@ public final class WebSocketModule extends ReactContextBaseJavaModule {
   public void connect(
     final String url,
     @Nullable final ReadableArray protocols,
-    @Nullable final ReadableMap headers,
+    @Nullable final ReadableMap options,
     final int id) {
     OkHttpClient client = new OkHttpClient.Builder()
       .connectTimeout(10, TimeUnit.SECONDS)
@@ -98,7 +98,9 @@ public final class WebSocketModule extends ReactContextBaseJavaModule {
       builder.addHeader("Cookie", cookie);
     }
 
-    if (headers != null) {
+    if (options != null && options.hasKey("headers") && options.getType("headers").equals(ReadableType.Map)) {
+
+      ReadableMap headers = options.getMap("headers");
       ReadableMapKeySetIterator iterator = headers.keySetIterator();
 
       if (!headers.hasKey("origin")) {