Make checks.py manageable from a permissions cog (#1547)

* This starts setting up checks.py to handle managed permission overrides

* missing else fix

* don't bypass is_owner, ever

* Modifies the predicates so that their inner functions are accesible from cogs without
being a check

* Update checks.py

Safety for existing permissions.py cogs

* block permissions cog from being unblocked by the permissions cog as a safety feature (really, co-owner exists at this point)

* un mix the 2 PRs (*sigh*)

* Update checks.py

remove debug prints that got lost inshuffle

redbot/core/checks.py

@@ -2,9 +2,26 @@ import discord
 from discord.ext import commands
 
 
+async def check_overrides(ctx, *, level):
+    if await ctx.bot.is_owner(ctx.author):
+        return True
+    perm_cog = ctx.bot.get_cog('Permissions')
+    if not perm_cog or ctx.cog == perm_cog:
+        return None
+    # don't break if someone loaded a cog named
+    # permissions that doesn't implement this
+    func = getattr(perm_cog, 'check_overrides', None)
+    val = None if func is None else await func(ctx, level)
+    return val
+
+
 def is_owner(**kwargs):
     async def check(ctx):
-        return await ctx.bot.is_owner(ctx.author, **kwargs)
+        override = await check_overrides(ctx, level='owner')
+        return (
+            override if override is not None
+            else await ctx.bot.is_owner(ctx.author, **kwargs)
+        )
     return commands.check(check)
 
 
@@ -15,14 +32,16 @@ async def check_permissions(ctx, perms):
         return False
     resolved = ctx.channel.permissions_for(ctx.author)
 
-    return all(getattr(resolved, name, None) == value for name, value in perms.items())
+    return all(
+        getattr(resolved, name, None) == value
+        for name, value in perms.items()
+    )
 
 
-def mod_or_permissions(**perms):
-    async def predicate(ctx):
-        has_perms_or_is_owner = await check_permissions(ctx, perms)
+async def is_mod_or_superior(ctx):
     if ctx.guild is None:
-            return has_perms_or_is_owner
+        return await ctx.bot.is_owner(ctx.author)
+    else:
         author = ctx.author
         settings = ctx.bot.db.guild(ctx.guild)
         mod_role_id = await settings.mod_role()
@@ -31,25 +50,50 @@ def mod_or_permissions(**perms):
         mod_role = discord.utils.get(ctx.guild.roles, id=mod_role_id)
         admin_role = discord.utils.get(ctx.guild.roles, id=admin_role_id)
 
-        is_staff = mod_role in author.roles or admin_role in author.roles
-        is_guild_owner = author == ctx.guild.owner
+        return (
+            await ctx.bot.is_owner(ctx.author)
+            or mod_role in author.roles
+            or admin_role in author.roles
+            or author == ctx.guild.owner
+        )
 
-        return is_staff or has_perms_or_is_owner or is_guild_owner
+
+async def is_admin_or_superior(ctx):
+    if ctx.guild is None:
+        return await ctx.bot.is_owner(ctx.author)
+    else:
+        author = ctx.author
+        settings = ctx.bot.db.guild(ctx.guild)
+        admin_role_id = await settings.admin_role()
+        admin_role = discord.utils.get(ctx.guild.roles, id=admin_role_id)
+
+        return (
+            await ctx.bot.is_owner(ctx.author)
+            or admin_role in author.roles
+            or author == ctx.guild.owner
+        )
+
+
+def mod_or_permissions(**perms):
+    async def predicate(ctx):
+        override = await check_overrides(ctx, level='mod')
+        return (
+            override if override is not None
+            else await check_permissions(ctx, perms)
+            or await is_mod_or_superior(ctx)
+        )
 
     return commands.check(predicate)
 
 
 def admin_or_permissions(**perms):
     async def predicate(ctx):
-        has_perms_or_is_owner = await check_permissions(ctx, perms)
-        if ctx.guild is None:
-            return has_perms_or_is_owner
-        author = ctx.author
-        is_guild_owner = author == ctx.guild.owner
-        admin_role_id = await ctx.bot.db.guild(ctx.guild).admin_role()
-        admin_role = discord.utils.get(ctx.guild.roles, id=admin_role_id)
-
-        return admin_role in author.roles or has_perms_or_is_owner or is_guild_owner
+        override = await check_overrides(ctx, level='admin')
+        return (
+            override if override is not None
+            else await check_permissions(ctx, perms)
+            or await is_admin_or_superior(ctx)
+        )
 
     return commands.check(predicate)
 
@@ -67,7 +111,11 @@ def guildowner_or_permissions(**perms):
             return has_perms_or_is_owner
         is_guild_owner = ctx.author == ctx.guild.owner
 
-        return is_guild_owner or has_perms_or_is_owner
+        override = await check_overrides(ctx, level='guildowner')
+        return (
+            override if override is not None
+            else is_guild_owner or has_perms_or_is_owner
+        )
 
     return commands.check(predicate)