From 576ac666d9848ac2a6d86e966d905075c1ff39d1 Mon Sep 17 00:00:00 2001
From: Lonami Exo <totufals@hotmail.com>
Date: Mon, 27 Aug 2018 01:19:37 +0200
Subject: [PATCH] Fix resolving events while disconnected

---
 telethon/client/updates.py    |  5 ++---
 telethon/events/common.py     | 38 +++++++++++++++--------------------
 telethon/events/newmessage.py |  7 +++----
 3 files changed, 21 insertions(+), 29 deletions(-)

diff --git a/telethon/client/updates.py b/telethon/client/updates.py
index 57cd4962..e92f1348 100644
--- a/telethon/client/updates.py
+++ b/telethon/client/updates.py
@@ -89,7 +89,6 @@ class UpdateMethods(UserMethods):
         elif not event:
             event = events.Raw()
 
-        event.ensure_resolve(self)
         self._event_builders.append((event, callback))
 
     def remove_event_handler(self, callback, event=None):
@@ -266,8 +265,8 @@ class UpdateMethods(UserMethods):
             if not event:
                 continue
 
-            if not builder.resolved.is_set():
-                await builder.resolved.wait()
+            if not builder.resolved:
+                await builder.resolve()
 
             if not builder.filter(event):
                 continue
diff --git a/telethon/events/common.py b/telethon/events/common.py
index 7c706e66..8c3d3360 100644
--- a/telethon/events/common.py
+++ b/telethon/events/common.py
@@ -58,37 +58,31 @@ class EventBuilder(abc.ABC):
     def __init__(self, chats=None, blacklist_chats=False):
         self.chats = chats
         self.blacklist_chats = blacklist_chats
-        self.resolved = None
+        self.resolved = False
+        self._resolve_lock = None
 
     @classmethod
     @abc.abstractmethod
     def build(cls, update):
         """Builds an event for the given update if possible, or returns None"""
 
-    def ensure_resolve(self, client):
-        """
-        Sets the event loop so that self.resolved can be used.
-
-        The expected workflow is:
-        1. Creating the event builder.
-        2a. Calling `ensure_resolve`.
-        2b. Awaiting `resolved.wait`.
-        OR
-        2a. Awaiting `resolve`.
-        3. Using `filter`.
-        """
-        if not self.resolved:
-            self.resolved = asyncio.Event(loop=client.loop)
-            client.loop.create_task(self.resolve(client))
-
     async def resolve(self, client):
         """Helper method to allow event builders to be resolved before usage"""
-        if not self.resolved.is_set():
-            self.chats = await _into_id_set(client, self.chats)
-            if not EventBuilder.self_id:
-                EventBuilder.self_id = await client.get_peer_id('me')
+        if self.resolved:
+            return
 
-            self.resolved.set()
+        if not self._resolve_lock:
+            self._resolve_lock = asyncio.Lock(loop=client.loop)
+
+        async with self._resolve_lock:
+            if not self.resolved:
+                await self._resolve(client)
+                self.resolved = True
+
+    async def _resolve(self, client):
+        self.chats = await _into_id_set(client, self.chats)
+        if not EventBuilder.self_id:
+            EventBuilder.self_id = await client.get_peer_id('me')
 
     def filter(self, event):
         """
diff --git a/telethon/events/newmessage.py b/telethon/events/newmessage.py
index b2ee33e1..12d3e7cb 100644
--- a/telethon/events/newmessage.py
+++ b/telethon/events/newmessage.py
@@ -71,10 +71,9 @@ class NewMessage(EventBuilder):
             self.from_users, self.forwards, self.from_users
         ))
 
-    async def resolve(self, client):
-        if not self.resolved.is_set():
-            self.from_users = await _into_id_set(client, self.from_users)
-            await super().resolve(client)
+    async def _resolve(self, client):
+        await super()._resolve(client)
+        self.from_users = await _into_id_set(client, self.from_users)
 
     @classmethod
     def build(cls, update):