Refactor error handling for system commands

src/pluralkit/bot/commands/system_commands.py

@@ -5,8 +5,7 @@ from datetime import datetime
 import pluralkit.utils
 from pluralkit.bot import help
 from pluralkit.bot.commands import *
-from pluralkit.errors import ExistingSystemError, DescriptionTooLongError, TagTooLongError, TagTooLongWithMembersError, \
-    InvalidAvatarURLError, UnlinkingLastAccountError
+from pluralkit.errors import ExistingSystemError, UnlinkingLastAccountError, PluralKitError, AccountAlreadyLinkedError
 
 logger = logging.getLogger("pluralkit.commands")
 
@@ -25,9 +24,8 @@ async def new_system(ctx: CommandContext):
 
     try:
         await System.create_system(ctx.conn, ctx.message.author.id, system_name)
-    except ExistingSystemError:
-        return CommandError(
-            "You already have a system registered. To delete your system, use `pk;system delete`, or to unlink your system from this account, use `pk;system unlink`.")
+    except ExistingSystemError as e:
+        return CommandError(e.message)
 
     return CommandSuccess("System registered! To begin adding members, use `pk;member new <name>`.")
 
@@ -55,21 +53,15 @@ async def system_set(ctx: CommandContext):
 
     if property_name not in properties:
         return CommandError(
-            "Unknown property {}. Allowed properties are {}.".format(property_name, ", ".join(allowed_properties)),
+            "Unknown property {}. Allowed properties are {}.".format(property_name, ", ".join(properties.keys())),
             help=help.edit_system)
 
     value = ctx.remaining() or None
 
     try:
         await properties[property_name](ctx.conn, value)
-    except DescriptionTooLongError:
-        return CommandError("You can't have a description longer than 1024 characters.")
-    except TagTooLongError:
-        return CommandError("You can't have a system tag longer than 32 characters.")
-    except TagTooLongWithMembersError as e:
-        return CommandError("The maximum length of a name plus the system tag is 32 characters. The following members would exceed the limit: {}. Please reduce the length of the tag, or rename the members.".format(", ".join(e.member_names)))
-    except InvalidAvatarURLError:
-        return CommandError("Invalid image URL.")
+    except PluralKitError as e:
+        return CommandError(e.message)
 
     response = CommandSuccess("{} system {}.".format("Updated" if value else "Cleared", property_name))
     # if prop == "avatar" and value:
@@ -89,7 +81,7 @@ async def system_link(ctx: CommandContext):
     # Make sure account doesn't already have a system
     account_system = await System.get_by_account(ctx.conn, linkee.id)
     if account_system:
-        return CommandError("The mentioned account is already linked to a system (`{}`)".format(account_system.hid))
+        return CommandError(AccountAlreadyLinkedError(account_system).message)
 
     if not await ctx.confirm_react(linkee, "{}, please confirm the link by clicking the ✅ reaction on this message.".format(linkee.mention)):
         return CommandError("Account link cancelled.")
@@ -103,8 +95,8 @@ async def system_unlink(ctx: CommandContext):
 
     try:
         await system.unlink_account(ctx.conn, ctx.message.author.id)
-    except UnlinkingLastAccountError:
-        return CommandError("This is the only account on your system, so you can't unlink it.")
+    except UnlinkingLastAccountError as e:
+        return CommandError(e.message)
 
     return CommandSuccess("Account unlinked.")
 

src/pluralkit/errors.py

@@ -1,36 +1,57 @@
+from typing import Tuple
+
+
 class PluralKitError(Exception):
-    pass
+    def __init__(self, message):
+        self.message = message
+        self.help_page = None
+
+    def with_help(self, help_page: Tuple[str, str]):
+        self.help_page = help_page
 
 
 class ExistingSystemError(PluralKitError):
-    pass
+    def __init__(self):
+        super().__init__("You already have a system registered. To delete your system, use `pk;system delete`, or to unlink your system from this account, use `pk;system unlink`.")
 
 
 class DescriptionTooLongError(PluralKitError):
-    pass
+    def __init__(self):
+        super().__init__("You can't have a description longer than 1024 characters.")
 
 
 class TagTooLongError(PluralKitError):
-    pass
+    def __init__(self):
+        super().__init__("You can't have a system tag longer than 32 characters.")
 
 
 class TagTooLongWithMembersError(PluralKitError):
     def __init__(self, member_names):
+        super().__init__("The maximum length of a name plus the system tag is 32 characters. The following members would exceed the limit: {}. Please reduce the length of the tag, or rename the members.".format(", ".join(member_names)))
         self.member_names = member_names
 
 
 class CustomEmojiError(PluralKitError):
-    pass
+    def __init__(self):
+        super().__init__("Due to a Discord limitation, custom emojis aren't supported. Please use a standard emoji instead.")
 
 
 class InvalidAvatarURLError(PluralKitError):
-    pass
+    def __init__(self):
+        super().__init__("Invalid image URL.")
+
+
+class AccountInOwnSystemError(PluralKitError):
+    def __init__(self):
+        super().__init__("That account is already linked to your own system.")
 
 
 class AccountAlreadyLinkedError(PluralKitError):
     def __init__(self, existing_system):
+        super().__init__("The mentioned account is already linked to a system (`{}`)".format(existing_system.hid))
         self.existing_system = existing_system
 
 
 class UnlinkingLastAccountError(PluralKitError):
-    pass
+    def __init__(self):
+        super().__init__("This is the only account on your system, so you can't unlink it.")

src/pluralkit/system.py

@@ -65,7 +65,11 @@ class System(namedtuple("System", ["id", "hid", "name", "description", "tag", "a
 
     async def link_account(self, conn, new_account_id: str):
         existing_system = await System.get_by_account(conn, new_account_id)
+
         if existing_system:
+            if existing_system.id == self.id:
+                raise errors.AccountInOwnSystemError()
+
             raise errors.AccountAlreadyLinkedError(existing_system)
 
         await db.link_account(conn, self.id, new_account_id)