[commands] Fix ext.commands help page full-width indentation

add _string_width function to util. Changed string width calculate
function from len() to util function _string_width().

discord/ext/commands/formatter.py

@@ -26,6 +26,7 @@ DEALINGS IN THE SOFTWARE.
 
 import itertools
 import inspect
+import discord.utils
 
 from .core import GroupMixin, Command
 from .errors import CommandError
@@ -172,7 +173,7 @@ class HelpFormatter:
         try:
             commands = self.command.all_commands if not self.is_cog() else self.context.bot.all_commands
             if commands:
-                return max(map(lambda c: len(c.name) if self.show_hidden or not c.hidden else 0, commands.values()))
+                return max(map(lambda c: discord.utils._string_width(c.name) if self.show_hidden or not c.hidden else 0, commands.values()))
             return 0
         except AttributeError:
             return len(self.command.name)
@@ -250,8 +251,8 @@ class HelpFormatter:
             if name in command.aliases:
                 # skip aliases
                 continue
-
+            width_gap = discord.utils._string_width(name) - len(name)
-            entry = '  {0:<{width}} {1}'.format(name, command.short_doc, width=max_width)
+            entry = '  {0:<{width}} {1}'.format(name, command.short_doc, width=max_width-width_gap)
             shortened = self.shorten(entry)
             self._paginator.add_line(shortened)
 

discord/utils.py

@@ -26,6 +26,7 @@ DEALINGS IN THE SOFTWARE.
 
 import array
 import asyncio
+import unicodedata
 from base64 import b64encode
 from bisect import bisect_left
 import datetime
@@ -39,6 +40,7 @@ import warnings
 from .errors import InvalidArgument
 
 DISCORD_EPOCH = 1420070400000
+UNICODE_WIDE_CHAR_TYPE = u"WFA"
 
 class cached_property:
     def __init__(self, function):
@@ -324,3 +326,10 @@ class SnowflakeList(array.array):
     def has(self, element):
         i = bisect_left(self, element)
         return i != len(self) and self[i] == element
+
+def _string_width(string):
+    """Returns string's width."""
+    width = 0
+    for char in string:
+        width += 2 if unicodedata.east_asian_width(char) in UNICODE_WIDE_CHAR_TYPE else 1
+    return width