HelpChannels: fix incomplete init of available channel set

If the cog is reloaded while there are less than the maximum amount of
available channels, it makes some channels available until the limit is
reached. When a channel is made available, it updates the
`available_help_channels` set. The `update_available_help_channels()`
function would not update this set if it saw that the set already
contains elements. This resulted in only the channels that were just
made available being in the set; the set would not contain the channels
that were already available when the bot started.

Fix this by unconditionally populating the set, but moving it to
`init_available()` so it only happens once.

Fix BOT-Z1
Fix #1715

1 files changed, 4 insertions, 5 deletions

diff --git a/bot/exts/help_channels/_cog.py b/bot/exts/help_channels/_cog.py
index afaf9b0bd..34fae7248 100644
--- a/bot/exts/help_channels/_cog.py
+++ b/bot/exts/help_channels/_cog.py
@@ -267,6 +267,10 @@ class HelpChannels(commands.Cog):
             for channel in channels[:abs(missing)]:
                 await self.unclaim_channel(channel, closed_on=_channel.ClosingReason.CLEANUP)
 
+        self.available_help_channels = {
+            c for c in self.available_category.channels if not _channel.is_excluded_channel(c)
+        }
+
         # Getting channels that need to be included in the dynamic message.
         await self.update_available_help_channels()
         log.trace("Dynamic available help message updated.")
@@ -519,11 +523,6 @@ class HelpChannels(commands.Cog):
 
     async def update_available_help_channels(self) -> None:
         """Updates the dynamic message within #how-to-get-help for available help channels."""
-        if not self.available_help_channels:
-            self.available_help_channels = set(
-                c for c in self.available_category.channels if not _channel.is_excluded_channel(c)
-            )
-
         available_channels = AVAILABLE_HELP_CHANNELS.format(
             available=", ".join(
                 c.mention for c in sorted(self.available_help_channels, key=attrgetter("position"))