Refactor human_join into its own private helper function

discord/app_commands/errors.py

@@ -28,6 +28,7 @@
 
 from ..enums import AppCommandOptionType, AppCommandType, Locale
 from ..errors import DiscordException, HTTPException, _flatten_error_dict
+from ..utils import _human_join
 
 __all__ = (
     'AppCommandError',
@@ -242,13 +243,7 @@ class MissingAnyRole(CheckFailure):
     def __init__(self, missing_roles: SnowflakeList) -> None:
         self.missing_roles: SnowflakeList = missing_roles
 
-        missing = [f"'{role}'" for role in missing_roles]
-
-        if len(missing) > 2:
-            fmt = '{}, or {}'.format(', '.join(missing[:-1]), missing[-1])
-        else:
-            fmt = ' or '.join(missing)
-
+        fmt = _human_join([f"'{role}'" for role in missing_roles])
         message = f'You are missing at least one of the required roles: {fmt}'
         super().__init__(message)
 
@@ -271,11 +266,7 @@ def __init__(self, missing_permissions: List[str], *args: Any) -> None:
         self.missing_permissions: List[str] = missing_permissions
 
         missing = [perm.replace('_', ' ').replace('guild', 'server').title() for perm in missing_permissions]
-
-        if len(missing) > 2:
-            fmt = '{}, and {}'.format(", ".join(missing[:-1]), missing[-1])
-        else:
-            fmt = ' and '.join(missing)
+        fmt = _human_join(missing, final='and')
         message = f'You are missing {fmt} permission(s) to run this command.'
         super().__init__(message, *args)
 
@@ -298,11 +289,7 @@ def __init__(self, missing_permissions: List[str], *args: Any) -> None:
         self.missing_permissions: List[str] = missing_permissions
 
         missing = [perm.replace('_', ' ').replace('guild', 'server').title() for perm in missing_permissions]
-
-        if len(missing) > 2:
-            fmt = '{}, and {}'.format(", ".join(missing[:-1]), missing[-1])
-        else:
-            fmt = ' and '.join(missing)
+        fmt = _human_join(missing, final='and')
         message = f'Bot requires {fmt} permission(s) to run this command.'
         super().__init__(message, *args)
 

discord/ext/commands/errors.py

@@ -27,6 +27,7 @@
 from typing import TYPE_CHECKING, Any, Callable, List, Optional, Tuple, Union
 
 from discord.errors import ClientException, DiscordException
+from discord.utils import _human_join
 
 if TYPE_CHECKING:
     from discord.abc import GuildChannel
@@ -758,12 +759,7 @@ def __init__(self, missing_roles: SnowflakeList) -> None:
         self.missing_roles: SnowflakeList = missing_roles
 
         missing = [f"'{role}'" for role in missing_roles]
-
-        if len(missing) > 2:
-            fmt = '{}, or {}'.format(', '.join(missing[:-1]), missing[-1])
-        else:
-            fmt = ' or '.join(missing)
-
+        fmt = _human_join(missing)
         message = f'You are missing at least one of the required roles: {fmt}'
         super().__init__(message)
 
@@ -788,12 +784,7 @@ def __init__(self, missing_roles: SnowflakeList) -> None:
         self.missing_roles: SnowflakeList = missing_roles
 
         missing = [f"'{role}'" for role in missing_roles]
-
-        if len(missing) > 2:
-            fmt = '{}, or {}'.format(', '.join(missing[:-1]), missing[-1])
-        else:
-            fmt = ' or '.join(missing)
-
+        fmt = _human_join(missing)
         message = f'Bot is missing at least one of the required roles: {fmt}'
         super().__init__(message)
 
@@ -832,11 +823,7 @@ def __init__(self, missing_permissions: List[str], *args: Any) -> None:
         self.missing_permissions: List[str] = missing_permissions
 
         missing = [perm.replace('_', ' ').replace('guild', 'server').title() for perm in missing_permissions]
-
-        if len(missing) > 2:
-            fmt = '{}, and {}'.format(', '.join(missing[:-1]), missing[-1])
-        else:
-            fmt = ' and '.join(missing)
+        fmt = _human_join(missing, final='and')
         message = f'You are missing {fmt} permission(s) to run this command.'
         super().__init__(message, *args)
 
@@ -857,11 +844,7 @@ def __init__(self, missing_permissions: List[str], *args: Any) -> None:
         self.missing_permissions: List[str] = missing_permissions
 
         missing = [perm.replace('_', ' ').replace('guild', 'server').title() for perm in missing_permissions]
-
-        if len(missing) > 2:
-            fmt = '{}, and {}'.format(', '.join(missing[:-1]), missing[-1])
-        else:
-            fmt = ' and '.join(missing)
+        fmt = _human_join(missing, final='and')
         message = f'Bot requires {fmt} permission(s) to run this command.'
         super().__init__(message, *args)
 
@@ -896,11 +879,7 @@ def _get_name(x):
                 return x.__class__.__name__
 
         to_string = [_get_name(x) for x in converters]
-        if len(to_string) > 2:
-            fmt = '{}, or {}'.format(', '.join(to_string[:-1]), to_string[-1])
-        else:
-            fmt = ' or '.join(to_string)
-
+        fmt = _human_join(to_string)
         super().__init__(f'Could not convert "{param.displayed_name or param.name}" into {fmt}.')
 
 
@@ -933,11 +912,7 @@ def __init__(self, param: Parameter, literals: Tuple[Any, ...], errors: List[Com
         self.argument: str = argument
 
         to_string = [repr(l) for l in literals]
-        if len(to_string) > 2:
-            fmt = '{}, or {}'.format(', '.join(to_string[:-1]), to_string[-1])
-        else:
-            fmt = ' or '.join(to_string)
-
+        fmt = _human_join(to_string)
         super().__init__(f'Could not convert "{param.displayed_name or param.name}" into the literal {fmt}.')
 
 

discord/ui/select.py

@@ -45,7 +45,7 @@
 from ..enums import ChannelType, ComponentType, SelectDefaultValueType
 from ..partial_emoji import PartialEmoji
 from ..emoji import Emoji
-from ..utils import MISSING
+from ..utils import MISSING, _human_join
 from ..components import (
     SelectOption,
     SelectMenu,
@@ -160,15 +160,7 @@ def _handle_select_defaults(
         object_type = obj.__class__ if not isinstance(obj, Object) else obj.type
 
         if not _is_valid_object_type(object_type, component_type, type_to_supported_classes):
-            # TODO: split this into a util function
-            supported_classes = [c.__name__ for c in type_to_supported_classes[component_type]]
-            if len(supported_classes) > 2:
-                supported_classes = ', '.join(supported_classes[:-1]) + f', or {supported_classes[-1]}'
-            elif len(supported_classes) == 2:
-                supported_classes = f'{supported_classes[0]} or {supported_classes[1]}'
-            else:
-                supported_classes = supported_classes[0]
-
+            supported_classes = _human_join([c.__name__ for c in type_to_supported_classes[component_type]])
             raise TypeError(f'Expected an instance of {supported_classes} not {object_type.__name__}')
 
         if object_type is Object:
@@ -1042,8 +1034,8 @@ def decorator(func: ItemCallbackType[V, BaseSelectT]) -> ItemCallbackType[V, Bas
             raise TypeError('select function must be a coroutine function')
         callback_cls = getattr(cls, '__origin__', cls)
         if not issubclass(callback_cls, BaseSelect):
-            supported_classes = ", ".join(["ChannelSelect", "MentionableSelect", "RoleSelect", "Select", "UserSelect"])
-            raise TypeError(f'cls must be one of {supported_classes} or a subclass of one of them, not {cls!r}.')
+            supported_classes = ', '.join(['ChannelSelect', 'MentionableSelect', 'RoleSelect', 'Select', 'UserSelect'])
+            raise TypeError(f'cls must be one of {supported_classes} or a subclass of one of them, not {cls.__name__}.')
 
         func.__discord_ui_model_type__ = callback_cls
         func.__discord_ui_model_kwargs__ = {

discord/utils.py

@@ -1380,3 +1380,17 @@ def _shorten(
 
 def _to_kebab_case(text: str) -> str:
     return CAMEL_CASE_REGEX.sub('-', text).lower()
+
+
+def _human_join(seq: Sequence[str], /, *, delimiter: str = ', ', final: str = 'or') -> str:
+    size = len(seq)
+    if size == 0:
+        return ''
+
+    if size == 1:
+        return seq[0]
+
+    if size == 2:
+        return f'{seq[0]} {final} {seq[1]}'
+
+    return delimiter.join(seq[:-1]) + f' {final} {seq[-1]}'