introduce isPackagerRunningAsync (#56004)

Summary:
Pull Request resolved: #56004

Changelog: [iOS][Added] Introduce "isPackagerRunningAsync" that does not block the ui thread waiting on the request to DevServer ("Packager") validating that it is running

The previous behavior was getting the UI blocked when the network conditions meant that a request was taking some time to result in success / fail / timeout.

Reviewed By: huntie

Differential Revision: D94430009

fbshipit-source-id: 6292ce74c027af7c217153620a03b417f30dff49

Author: vzaidman

packages/react-native/React/Base/RCTBundleURLProvider.h

@@ -57,6 +57,23 @@ NS_ASSUME_NONNULL_BEGIN
  */
 + (BOOL)isPackagerRunning:(NSString *)hostPort scheme:(NSString *__nullable)scheme;
 
+/**
+ * Asynchronously checks if there's a packager running at the given host:port.
+ * The port is optional, if not specified, kRCTBundleURLProviderDefaultPort will be used
+ * The completion handler is called on an arbitrary queue.
+ */
++ (void)isPackagerRunningAsync:(NSString *)hostPort completion:(void (^)(BOOL isRunning))completion;
+
+/**
+ * Asynchronously checks if there's a packager running at the given scheme://host:port.
+ * The port is optional, if not specified, kRCTBundleURLProviderDefaultPort will be used
+ * The scheme is also optional, if not specified, a default http protocol will be used
+ * The completion handler is called on an arbitrary queue.
+ */
++ (void)isPackagerRunningAsync:(NSString *)hostPort
+                        scheme:(NSString *__nullable)scheme
+                    completion:(void (^)(BOOL isRunning))completion;
+
 /**
  * Returns the jsBundleURL for a given bundle entrypoint and
  * the fallback offline JS bundle if the packager is not running.

packages/react-native/React/Base/RCTBundleURLProvider.mm

@@ -94,6 +94,9 @@ + (BOOL)isPackagerRunning:(NSString *)hostPort scheme:(NSString *)scheme
   }
 
   NSURL *url = [serverRootWithHostPort(hostPort, scheme) URLByAppendingPathComponent:@"status"];
+  if (url == nil) {
+    return NO;
+  }
 
   NSURLSession *session = [NSURLSession sharedSession];
   NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
@@ -133,6 +136,73 @@ + (BOOL)isPackagerRunning:(NSString *)hostPort scheme:(NSString *)scheme
   return isRunning;
 }
 
++ (void)isPackagerRunningAsync:(NSString *)hostPort completion:(void (^)(BOOL isRunning))completion
+{
+  [RCTBundleURLProvider isPackagerRunningAsync:hostPort scheme:nil completion:completion];
+}
+
++ (void)isPackagerRunningAsync:(NSString *)hostPort
+                        scheme:(NSString *)scheme
+                    completion:(void (^)(BOOL isRunning))completion
+{
+  if (!kRCTAllowPackagerAccess) {
+    completion(NO);
+    return;
+  }
+
+  NSURL *url = [serverRootWithHostPort(hostPort, scheme) URLByAppendingPathComponent:@"status"];
+  if (url == nil) {
+    completion(NO);
+    return;
+  }
+
+  NSURLSession *session = [NSURLSession sharedSession];
+  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
+                                                         cachePolicy:NSURLRequestUseProtocolCachePolicy
+                                                     timeoutInterval:kRCTPackagerStatusRequestTimeout];
+  [[RCTDevSupportHttpHeaders sharedInstance] applyHeadersToRequest:request];
+
+  __block BOOL hasCompleted = NO;
+  NSObject *lock = [[NSObject alloc] init];
+
+  void (^safeCompletion)(BOOL) = ^(BOOL isRunning) {
+    @synchronized(lock) {
+      if (!hasCompleted) {
+        hasCompleted = YES;
+        completion(isRunning);
+      }
+    }
+  };
+
+  NSURLSessionDataTask *task = [session dataTaskWithRequest:request
+                                          completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
+                                            if (error != nil || data == nil) {
+                                              safeCompletion(NO);
+                                              return;
+                                            }
+                                            NSString *status = [[NSString alloc] initWithData:data
+                                                                                     encoding:NSUTF8StringEncoding];
+                                            BOOL isRunning = [status isEqualToString:@"packager-status:running"];
+                                            safeCompletion(isRunning);
+                                          }];
+  [task resume];
+
+  dispatch_after(
+      dispatch_time(
+          DISPATCH_TIME_NOW,
+          (int64_t)((kRCTPackagerStatusRequestTimeout + kRCTPackagerStatusRequestTimeoutGraceTime) * NSEC_PER_SEC)),
+      dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
+      ^{
+        @synchronized(lock) {
+          if (!hasCompleted) {
+            hasCompleted = YES;
+            [task cancel];
+            completion(NO);
+          }
+        }
+      });
+}
+
 - (NSString *)guessPackagerHost
 {
   static NSString *ipGuess;
@@ -160,6 +230,18 @@ + (BOOL)isPackagerRunning:(NSString *)hostPort scheme:(NSString *)scheme
 {
   return false;
 }
+
++ (void)isPackagerRunningAsync:(NSString *)hostPort completion:(void (^)(BOOL isRunning))completion
+{
+  completion(NO);
+}
+
++ (void)isPackagerRunningAsync:(NSString *)hostPort
+                        scheme:(NSString *)scheme
+                    completion:(void (^)(BOOL isRunning))completion
+{
+  completion(NO);
+}
 #endif
 
 - (NSString *)packagerServerHost