Attempt at fixing #5 (RPCError) and updated README

Now RPC results can be received from the updates thread, as long
as they are errors. This, however, should not happen!
A recursive lock is now used (and released on every method, rather
than only on the `.receive()` one)

README.md

@@ -14,7 +14,6 @@ The project's **core only** is based on TLSharp, a C# Telegram client implementa
   - [Tips for porting Telethon](#tips-for-porting-telethon)
   - [Code generator limitations](#code-generator-limitations)
   - [Updating the `scheme.tl`](#updating-the-schemetl)
-- [Plans for the future](#plans-for-the-future)
 
 ## Why Telethon?
 > Why should I bother with Telethon? There are more mature projects already, such as

telethon/network/mtproto_sender.py

@@ -1,7 +1,7 @@
 import gzip
 from telethon.errors import *
 from time import sleep
-from threading import Thread, Lock
+from threading import Thread, RLock
 
 import telethon.helpers as utils
 from telethon.crypto import AES
@@ -19,8 +19,12 @@ class MtProtoSender:
         self.need_confirmation = []  # Message IDs that need confirmation
         self.on_update_handlers = []
 
-        # Store a Lock instance to make this class safely multi-threaded
+        # Store an RLock instance to make this class safely multi-threaded
-        self.lock = Lock()
+        self.lock = RLock()
+
+        # Flag used to determine whether we've received a sent request yet or not
+        # We need this to avoid using the updates thread if we're waiting to read
+        self.waiting_receive = False
 
         self.updates_thread = Thread(target=self.updates_thread_method, name='Updates thread')
         self.updates_thread_running = False
@@ -68,7 +72,7 @@ class MtProtoSender:
 
     # region Send and receive
 
-    def send(self, request, resend=False):
+    def send(self, request):
         """Sends the specified MTProtoRequest, previously sending any message
            which needed confirmation. This also pauses the updates thread"""
 
@@ -78,9 +82,10 @@ class MtProtoSender:
         if self.updates_thread_receiving:
             self.transport.cancel_receive()
 
-        # Now only us can be using this method if we're not resending
+        # Now only us can be using this method
-        if not resend:
+        with self.lock:
-            self.lock.acquire()
+            # Set the flag to true so the updates thread stops trying to receive
+            self.waiting_receive = True
 
             # If any message needs confirmation send an AckRequest first
             if self.need_confirmation:
@@ -98,14 +103,12 @@ class MtProtoSender:
 
             # And update the saved session
             self.session.save()
-        # Don't resume the updates thread yet,
-        # since every send() is preceded by a receive()
 
     def receive(self, request):
         """Receives the specified MTProtoRequest ("fills in it"
            the received data). This also restores the updates thread"""
 
-        try:
+        with self.lock:
             # Don't stop trying to receive until we get the request we wanted
             while not request.confirm_received:
                 seq, body = self.transport.receive()
@@ -114,10 +117,8 @@ class MtProtoSender:
                 with BinaryReader(message) as reader:
                     self.process_msg(remote_msg_id, remote_sequence, reader, request)
 
-        finally:
+            # We can now set the flag to False thus resuming the updates thread
-            # Once we are done trying to get our request,
+            self.waiting_receive = False
-            # restore the updates thread and release the lock
-            self.lock.release()
 
     # endregion
 
@@ -252,7 +253,7 @@ class MtProtoSender:
             raise ValueError('Tried to handle a bad server salt with no request specified')
 
         # Resend
-        self.send(request, resend=True)
+        self.send(request)
 
         return True
 
@@ -265,19 +266,19 @@ class MtProtoSender:
         raise BadMessageError(error_code)
 
     def handle_rpc_result(self, msg_id, sequence, reader, request):
-        if not request:
-            raise ValueError('RPC results should only happen after a request was sent')
-
         code = reader.read_int(signed=False)
         request_id = reader.read_long(signed=False)
         inner_code = reader.read_int(signed=False)
 
-        if request_id == request.msg_id:
+        if request and request_id == request.msg_id:
             request.confirm_received = True
 
         if inner_code == 0x2144ca19:  # RPC Error
             error = RPCError(code=reader.read_int(), message=reader.tgread_string())
             if error.must_resend:
+                if not request:
+                    raise ValueError('The previously sent request must be resent. '
+                                     'However, no request was previously sent (called from updates thread).')
                 request.confirm_received = False
 
             if error.message.startswith('FLOOD_WAIT_'):
@@ -290,6 +291,9 @@ class MtProtoSender:
             else:
                 raise error
         else:
+            if not request:
+                raise ValueError('Cannot receive a request from inside an RPC result from the updates thread.')
+
             if inner_code == 0x3072cfa1:  # GZip packed
                 unpacked_data = gzip.decompress(reader.tgread_bytes())
                 with BinaryReader(unpacked_data) as compressed_reader:
@@ -323,6 +327,8 @@ class MtProtoSender:
     def updates_thread_method(self):
         """This method will run until specified and listen for incoming updates"""
         while self.updates_thread_running:
+            # Only try to receive updates if we're not waiting to receive a request
+            if not self.waiting_receive:
                 with self.lock:
                     try:
                         self.updates_thread_receiving = True