Add PartialEmoji.from_str helper

2 files changed, 46 insertions, 22 deletions

diff --git a/discord/partial_emoji.py b/discord/partial_emoji.py
index c9ddd650..fc40ff55 100644
--- a/discord/partial_emoji.py
+++ b/discord/partial_emoji.py
@@ -25,6 +25,7 @@ DEALINGS IN THE SOFTWARE.
 from __future__ import annotations
 
 from typing import Any, Dict, Optional, TYPE_CHECKING, Type, TypeVar
+import re
 
 from .asset import Asset, AssetMixin
 from .errors import InvalidArgument
@@ -88,6 +89,8 @@ class PartialEmoji(_EmojiTag, AssetMixin):
 
     __slots__ = ('animated', 'name', 'id', '_state')
 
+    _CUSTOM_EMOJI_RE = re.compile(r'<?(?P<animated>a)?:?(?P<name>[A-Za-z0-9\_]+):(?P<id>[0-9]{13,20})>?')
+
     if TYPE_CHECKING:
         id: Optional[int]
 
@@ -105,6 +108,41 @@ class PartialEmoji(_EmojiTag, AssetMixin):
             name=data.get('name', ''),
         )
 
+    @classmethod
+    def from_str(cls: Type[PE], value: str) -> PE:
+        """Converts a Discord string representation of an emoji to a :class:`PartialEmoji`.
+
+        The formats accepted are:
+
+        - ``a:name:id``
+        - ``<a:name:id>``
+        - ``name:id``
+        - ``<:name:id>``
+
+        If the format does not match then it is assumed to be a unicode emoji.
+
+        .. versionadded:: 2.0
+
+        Parameters
+        ------------
+        value: :class:`str`
+            The string representation of an emoji.
+
+        Returns
+        --------
+        :class:`PartialEmoji`
+            The partial emoji from this string.
+        """
+        match = cls._CUSTOM_EMOJI_RE.match(value)
+        if match is not None:
+            groups = match.groupdict()
+            animated = bool(groups['animated'])
+            emoji_id = int(groups['id'])
+            name = groups['name']
+            return cls(name=name, animated=animated, id=emoji_id)
+
+        return cls(name=value, id=None, animated=False)
+
     def to_dict(self) -> Dict[str, Any]:
         o: Dict[str, Any] = {'name': self.name}
         if self.id:
diff --git a/discord/ui/button.py b/discord/ui/button.py
index 72956562..ca32098d 100644
--- a/discord/ui/button.py
+++ b/discord/ui/button.py
@@ -26,7 +26,6 @@ from __future__ import annotations
 
 from typing import Callable, Optional, TYPE_CHECKING, Tuple, Type, TypeVar, Union
 import inspect
-import re
 import os
 
 
@@ -43,25 +42,6 @@ __all__ = (
 if TYPE_CHECKING:
     from .view import View
 
-_custom_emoji = re.compile(r'<?(?P<animated>a)?:?(?P<name>[A-Za-z0-9\_]+):(?P<id>[0-9]{13,20})>?')
-
-
-def _to_partial_emoji(obj: Union[str, PartialEmoji], *, _custom_emoji=_custom_emoji) -> PartialEmoji:
-    if isinstance(obj, PartialEmoji):
-        return obj
-
-    obj = str(obj)
-    match = _custom_emoji.match(obj)
-    if match is not None:
-        groups = match.groupdict()
-        animated = bool(groups['animated'])
-        emoji_id = int(groups['id'])
-        name = groups['name']
-        return PartialEmoji(name=name, animated=animated, id=emoji_id)
-
-    return PartialEmoji(name=obj, id=None, animated=False)
-
-
 B = TypeVar('B', bound='Button')
 V = TypeVar('V', bound='View', covariant=True)
 
@@ -118,6 +98,9 @@ class Button(Item[V]):
         if url is not None:
             style = ButtonStyle.link
 
+        if isinstance(emoji, str):
+            emoji = PartialEmoji.from_str(emoji)
+
         self._underlying = ButtonComponent._raw_construct(
             type=ComponentType.button,
             custom_id=custom_id,
@@ -125,7 +108,7 @@ class Button(Item[V]):
             disabled=disabled,
             label=label,
             style=style,
-            emoji=None if emoji is None else _to_partial_emoji(emoji),
+            emoji=emoji,
         )
         self.group_id = group
 
@@ -190,7 +173,10 @@ class Button(Item[V]):
     @emoji.setter
     def emoji(self, value: Optional[Union[str, PartialEmoji]]):  # type: ignore
         if value is not None:
-            self._underlying.emoji = _to_partial_emoji(value)
+            if isinstance(value, str):
+                self._underlying.emoji = PartialEmoji.from_str(value)
+            else:
+                self._underlying.emoji = value
         else:
             self._underlying.emoji = None