Bot: add wait_until_guild_available

This coroutine waits until the configured guild is available and
ensures the cache is present.

The on_ready event is inadequate because it only waits 2 seconds for a
GUILD_CREATE gateway event before giving up and thus not populating the
cache for unavailable guilds.

1 files changed, 39 insertions, 0 deletions

diff --git a/bot/bot.py b/bot/bot.py
index 8f808272f..c0f31911c 100644
--- a/bot/bot.py
+++ b/bot/bot.py
@@ -1,11 +1,14 @@
+import asyncio
 import logging
 import socket
 from typing import Optional
 
 import aiohttp
+import discord
 from discord.ext import commands
 
 from bot import api
+from bot import constants
 
 log = logging.getLogger('bot')
 
@@ -24,6 +27,8 @@ class Bot(commands.Bot):
 
         super().__init__(*args, connector=self.connector, **kwargs)
 
+        self._guild_available = asyncio.Event()
+
         self.http_session: Optional[aiohttp.ClientSession] = None
         self.api_client = api.APIClient(loop=self.loop, connector=self.connector)
 
@@ -51,3 +56,37 @@ class Bot(commands.Bot):
         self.http_session = aiohttp.ClientSession(connector=self.connector)
 
         await super().start(*args, **kwargs)
+
+    async def on_guild_available(self, guild: discord.Guild) -> None:
+        """
+        Set the internal guild available event when constants.Guild.id becomes available.
+
+        If the cache appears to still be empty (no members, no channels, or no roles), the event
+        will not be set.
+        """
+        if guild.id != constants.Guild.id:
+            return
+
+        if not guild.roles or not guild.members or not guild.channels:
+            log.warning(
+                "Guild available event was dispatched but the cache appears to still be empty!"
+            )
+            return
+
+        self._guild_available.set()
+
+    async def on_guild_unavailable(self, guild: discord.Guild) -> None:
+        """Clear the internal guild available event when constants.Guild.id becomes unavailable."""
+        if guild.id != constants.Guild.id:
+            return
+
+        self._guild_available.clear()
+
+    async def wait_until_guild_available(self) -> None:
+        """
+        Wait until the constants.Guild.id guild is available (and the cache is ready).
+
+        The on_ready event is inadequate because it only waits 2 seconds for a GUILD_CREATE
+        gateway event before giving up and thus not populating the cache for unavailable guilds.
+        """
+        await self._guild_available.wait()