[V3 JSON] Drivers deepcopy input/output data (#1855)

* [V3 JSON] Return deepcopy in JSON driver

* Add a test

* foo not bar

* Add a test for setting and then mutating

* Resolve issue for setting and mutating as well

* Reformat

redbot/core/config.py

@@ -335,7 +335,7 @@ class Group(Value):
                 default = poss_default
 
         try:
-            return deepcopy(await self.driver.get(*self.identifiers, *path))
+            return await self.driver.get(*self.identifiers, *path)
         except KeyError:
             if default is not ...:
                 return default
@@ -365,7 +365,7 @@ class Group(Value):
 
         """
         if not defaults:
-            defaults = deepcopy(self.defaults)
+            defaults = self.defaults
 
         for key, value in current.items():
             if isinstance(value, collections.Mapping):

redbot/core/drivers/red_json.py

@@ -1,5 +1,6 @@
 from pathlib import Path
 from typing import Tuple
+import copy
 import weakref
 import logging
 
@@ -97,7 +98,7 @@ class JSON(BaseDriver):
         full_identifiers = (self.unique_cog_identifier, *identifiers)
         for i in full_identifiers:
             partial = partial[i]
-        return partial
+        return copy.deepcopy(partial)
 
     async def set(self, *identifiers: str, value=None):
         partial = self.data
@@ -107,7 +108,7 @@ class JSON(BaseDriver):
                 partial[i] = {}
             partial = partial[i]
 
-        partial[full_identifiers[-1]] = value
+        partial[full_identifiers[-1]] = copy.deepcopy(value)
         await self.jsonIO._threadsafe_save_json(self.data)
 
     async def clear(self, *identifiers: str):

tests/core/test_config.py

@@ -379,13 +379,9 @@ async def test_value_ctxmgr_saves(config):
 async def test_value_ctxmgr_immutable(config):
     config.register_global(foo=True)
 
-    try:
+    with pytest.raises(TypeError):
         async with config.foo() as foo:
             foo = False
-    except TypeError:
-        pass
-    else:
-        raise AssertionError
 
     foo = await config.foo()
     assert foo is True
@@ -401,3 +397,25 @@ async def test_ctxmgr_no_shared_default(config, member_factory):
         foo.append(1)
 
     assert 1 not in await config.member(m2).foo()
+
+
+@pytest.mark.asyncio
+async def test_get_then_mutate(config):
+    """Tests that mutating an object after getting it as a value doesn't mutate the data store."""
+    config.register_global(list1=[])
+    await config.list1.set([])
+    list1 = await config.list1()
+    list1.append("foo")
+    list1 = await config.list1()
+    assert "foo" not in list1
+
+
+@pytest.mark.asyncio
+async def test_set_then_mutate(config):
+    """Tests that mutating an object after setting it as a value doesn't mutate the data store."""
+    config.register_global(list1=[])
+    list1 = []
+    await config.list1.set(list1)
+    list1.append("foo")
+    list1 = await config.list1()
+    assert "foo" not in list1