Add CommandTree.get_hash

discord/app_commands/tree.py

@@ -25,6 +25,8 @@
 from __future__ import annotations
 import logging
 import inspect
+import sys
+from hashlib import blake2b
 
 from typing import (
     Any,
@@ -62,7 +64,7 @@
 from .translator import Translator, locale_str
 from ..errors import ClientException, HTTPException
 from ..enums import AppCommandType, InteractionType
-from ..utils import MISSING, _get_as_snowflake, _is_submodule, _shorten
+from ..utils import MISSING, _get_as_snowflake, _is_submodule, _shorten, _to_json
 from .._types import ClientT
 
 
@@ -82,6 +84,25 @@
 _log = logging.getLogger(__name__)
 
 
+if sys.version_info < (3, 9):
+    _blake_kwargs = {}
+else:
+    # This prevents blake from raising an error
+    # with some configurations in python 3.9
+    _blake_kwargs = {'usedforsecurity': False}
+
+
+def _hash_payload(payload: list[Dict[str, Any]]) -> bytes:
+    tree_hash = blake2b(digest_size=32, person=b"tree", last_node=True, **_blake_kwargs)
+    command_hashes = [
+        blake2b(_to_json(c).encode(), person=b"command", last_node=False, **_blake_kwargs).digest() for c in payload
+    ]
+    for h in sorted(command_hashes):
+        tree_hash.update(h)
+
+    return b"v1:" + tree_hash.digest()
+
+
 def _retrieve_guild_ids(
     command: Any, guild: Optional[Snowflake] = MISSING, guilds: Sequence[Snowflake] = MISSING
 ) -> Optional[Set[int]]:
@@ -1076,6 +1097,17 @@ async def set_translator(self, translator: Optional[Translator]) -> None:
             await translator.load()
             self._state._translator = translator
 
+    async def _get_payload(self, *, guild: Optional[Snowflake] = None) -> List[Dict[str, Any]]:
+        commands = self._get_all_commands(guild=guild)
+
+        translator = self.translator
+        if translator:
+            payload = [await command.get_translated_payload(self, translator) for command in commands]
+        else:
+            payload = [command.to_dict(self) for command in commands]
+
+        return payload
+
     async def sync(self, *, guild: Optional[Snowflake] = None) -> List[AppCommand]:
         """|coro|
 
@@ -1116,13 +1148,7 @@ async def sync(self, *, guild: Optional[Snowflake] = None) -> List[AppCommand]:
         if self.client.application_id is None:
             raise MissingApplicationID
 
-        commands = self._get_all_commands(guild=guild)
-
-        translator = self.translator
-        if translator:
-            payload = [await command.get_translated_payload(self, translator) for command in commands]
-        else:
-            payload = [command.to_dict(self) for command in commands]
+        payload = await self._get_payload(guild=guild)
 
         try:
             if guild is None:
@@ -1131,7 +1157,7 @@ async def sync(self, *, guild: Optional[Snowflake] = None) -> List[AppCommand]:
                 data = await self._http.bulk_upsert_guild_commands(self.client.application_id, guild.id, payload=payload)
         except HTTPException as e:
             if e.status == 400 and e.code == 50035:
-                raise CommandSyncFailure(e, commands) from None
+                raise CommandSyncFailure(e, self._get_all_commands(guild=guild)) from None
             raise
 
         return [AppCommand(data=d, state=self._state) for d in data]
@@ -1315,3 +1341,30 @@ async def _call(self, interaction: Interaction[ClientT]) -> None:
         else:
             if not interaction.command_failed:
                 self.client.dispatch('app_command_completion', interaction, command)
+
+    async def get_hash(self, *, guild: Optional[Snowflake] = None) -> bytes:
+        """|coro|
+
+        Returns a hash for tree's state, either for the global tree
+        if no guild is provided, or the guild specific portions of
+        the tree if a guild is provided.
+
+        This can be used to avoid uneccessary syncing.
+
+        .. versionadded:: 2.5
+
+        Parameters
+        -----------
+        guild: Optional[:class:`~discord.abc.Snowflake`]
+            The guild to get the tree hash for. If ``None`` then then
+            the hash for all global commands instead.
+
+            This corresponds to the guild parameter used when syncing.
+
+        Returns
+        -------
+        bytes
+            A hash of the tree's state as it would be synced.
+        """
+        payload = await self._get_payload(guild=guild)
+        return _hash_payload(payload)