Add support for clearing a specific reaction.

Closes #2440

5 files changed, 117 insertions, 1 deletions

diff --git a/discord/http.py b/discord/http.py
index 0c0a5497..3789b3c8 100644
--- a/discord/http.py
+++ b/discord/http.py
@@ -402,6 +402,11 @@ class HTTPClient:
 
         return self.request(r)
 
+    def clear_single_reaction(self, channel_id, message_id, emoji):
+        r = Route('DELETE', '/channels/{channel_id}/messages/{message_id}/reactions/{emoji}',
+                   channel_id=channel_id, message_id=message_id, emoji=emoji)
+        return self.request(r)
+
     def get_message(self, channel_id, message_id):
         r = Route('GET', '/channels/{channel_id}/messages/{message_id}', channel_id=channel_id, message_id=message_id)
         return self.request(r)
@@ -425,7 +430,7 @@ class HTTPClient:
         return self.request(Route('GET', '/channels/{channel_id}/messages', channel_id=channel_id), params=params)
 
     def publish_message(self, channel_id, message_id):
-        return self.request(Route('POST', '/channels/{channel_id}/messages/{message_id}/crosspost', 
+        return self.request(Route('POST', '/channels/{channel_id}/messages/{message_id}/crosspost',
                                   channel_id=channel_id, message_id=message_id))
 
     def pin_message(self, channel_id, message_id):
diff --git a/discord/message.py b/discord/message.py
index e2ae7193..4010a2c3 100644
--- a/discord/message.py
+++ b/discord/message.py
@@ -371,6 +371,18 @@ class Message:
 
         return reaction
 
+    def _clear_emoji(self, emoji):
+        to_check = str(emoji)
+        for index, reaction in enumerate(self.reactions):
+            if str(reaction.emoji) == to_check:
+                break
+        else:
+            # didn't find anything so just return
+            return
+
+        del self.reactions[index]
+        return reaction
+
     def _update(self, data):
         handlers = self._HANDLERS
         for key, value in data.items():
@@ -945,6 +957,37 @@ class Message:
         else:
             await self._state.http.remove_reaction(self.channel.id, self.id, emoji, member.id)
 
+    async def clear_reaction(self, emoji):
+        """|coro|
+
+        Clears a specific reaction from the message.
+
+        The emoji may be a unicode emoji or a custom guild :class:`Emoji`.
+
+        You need the :attr:`~Permissions.manage_messages` permission to use this.
+
+        .. versionadded:: 1.3
+
+        Parameters
+        -----------
+        emoji: Union[:class:`Emoji`, :class:`Reaction`, :class:`PartialEmoji`, :class:`str`]
+            The emoji to clear.
+
+        Raises
+        --------
+        HTTPException
+            Clearing the reaction failed.
+        Forbidden
+            You do not have the proper permissions to clear the reaction.
+        NotFound
+            The emoji you specified was not found.
+        InvalidArgument
+            The emoji parameter is invalid.
+        """
+
+        emoji = self._emoji_reaction(emoji)
+        await self._state.http.clear_single_reaction(self.channel.id, self.id, emoji)
+
     @staticmethod
     def _emoji_reaction(emoji):
         if isinstance(emoji, Reaction):
diff --git a/discord/raw_models.py b/discord/raw_models.py
index 1f318564..dc094e34 100644
--- a/discord/raw_models.py
+++ b/discord/raw_models.py
@@ -177,3 +177,32 @@ class RawReactionClearEvent(_RawReprMixin):
             self.guild_id = int(data['guild_id'])
         except KeyError:
             self.guild_id = None
+
+class RawReactionClearEmojiEvent(_RawReprMixin):
+    """Represents the payload for a :func:`on_raw_reaction_clear_emoji` event.
+
+    .. versionadded:: 1.3.0
+
+    Attributes
+    -----------
+    message_id: :class:`int`
+        The message ID that got its reactions cleared.
+    channel_id: :class:`int`
+        The channel ID where the reactions got cleared.
+    guild_id: Optional[:class:`int`]
+        The guild ID where the reactions got cleared.
+    emoji: :class:`PartialEmoji`
+        The custom or unicode emoji being removed.
+    """
+
+    __slots__ = ('message_id', 'channel_id', 'guild_id', 'emoji')
+
+    def __init__(self, data, emoji):
+        self.emoji = emoji
+        self.message_id = int(data['message_id'])
+        self.channel_id = int(data['channel_id'])
+
+        try:
+            self.guild_id = int(data['guild_id'])
+        except KeyError:
+            self.guild_id = None
diff --git a/discord/reaction.py b/discord/reaction.py
index c7f2ef77..79c8efe2 100644
--- a/discord/reaction.py
+++ b/discord/reaction.py
@@ -121,6 +121,28 @@ class Reaction:
 
         await self.message.remove_reaction(self.emoji, user)
 
+    async def clear(self):
+        """|coro|
+
+        Clears this reaction from the message.
+
+        You need the :attr:`~Permissions.manage_messages` permission to use this.
+
+        .. versionadded:: 1.3
+
+        Raises
+        --------
+        HTTPException
+            Clearing the reaction failed.
+        Forbidden
+            You do not have the proper permissions to clear the reaction.
+        NotFound
+            The emoji you specified was not found.
+        InvalidArgument
+            The emoji parameter is invalid.
+        """
+        await self.message.clear_reaction(self.emoji)
+
     def users(self, limit=None, after=None):
         """Returns an :class:`AsyncIterator` representing the users that have reacted to the message.
 
diff --git a/discord/state.py b/discord/state.py
index aea0984d..a3a8e243 100644
--- a/discord/state.py
+++ b/discord/state.py
@@ -509,6 +509,23 @@ class ConnectionState:
                 if user:
                     self.dispatch('reaction_remove', reaction, user)
 
+    def parse_message_reaction_remove_emoji(self, data):
+        emoji = data['emoji']
+        emoji_id = utils._get_as_snowflake(emoji, 'id')
+        emoji = PartialEmoji.with_state(self, animated=emoji.get('animated', False), id=emoji_id, name=emoji['name'])
+        raw = RawReactionClearEmojiEvent(data, emoji)
+        self.dispatch('raw_reaction_clear_emoji', raw)
+
+        message = self._get_message(raw.message_id)
+        if message is not None:
+            try:
+                reaction = message._clear_emoji(emoji)
+            except (AttributeError, ValueError): # eventual consistency lol
+                pass
+            else:
+                if reaction:
+                    self.dispatch('reaction_clear_emoji', reaction)
+
     def parse_presence_update(self, data):
         guild_id = utils._get_as_snowflake(data, 'guild_id')
         guild = self._get_guild(guild_id)