From 1d2eaf852627f5fe152653bae82d1a161d38b5a1 Mon Sep 17 00:00:00 2001
From: Sebastian Law <sebnlaw@gmail.com>
Date: Thu, 19 Aug 2021 16:56:28 -0700
Subject: [PATCH] [commands] reset view  when Optional argument encounters
 parsing error

---
 discord/ext/commands/core.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/discord/ext/commands/core.py b/discord/ext/commands/core.py
index 88e65507d..2d58f95ae 100644
--- a/discord/ext/commands/core.py
+++ b/discord/ext/commands/core.py
@@ -564,7 +564,14 @@ class Command(_BaseCommand, Generic[CogT, P, T]):
         if consume_rest_is_special:
             argument = view.read_rest().strip()
         else:
-            argument = view.get_quoted_word()
+            try:
+                argument = view.get_quoted_word()
+            except ArgumentParsingError as exc:
+                if self._is_typing_optional(param.annotation):
+                    view.index = previous
+                    return None
+                else:
+                    raise exc
         view.previous = previous
 
         # type-checker fails to narrow argument