Restore support to do template-syntax lookups for nested dicts.

This patch skips the lookup for regular "single" key-access to not return default value from defaultdicts. Nested defaultdicts will however return the default value instead of "missing" due to how Django's Variable.resolve(key) works.

ninja/schema.py

@@ -66,21 +66,30 @@ def __getattr__(self, key: str) -> Any:
         if resolver:
             value = resolver(getter=self)
         else:
+            resolve = False
             if isinstance(self._obj, dict):
-                if key not in self._obj:
+                if key in self._obj:
+                    value = self._obj[key]
+                elif '.' in key and not key.startswith('_'):
+                    # Only do template lookup if necessary, which will also work around
+                    # Variable.resolve() returning default value of defaultdict's
+                    resolve = True
+                else:
                     raise AttributeError(key)
-                value = self._obj[key]
             else:
                 try:
                     value = getattr(self._obj, key)
                 except AttributeError:
-                    try:
-                        # value = attrgetter(key)(self._obj)
-                        value = Variable(key).resolve(self._obj)
-                        # TODO: Variable(key) __init__ is actually slower than
-                        #       Variable.resolve - so it better be cached
-                    except VariableDoesNotExist as e:
-                        raise AttributeError(key) from e
+                    resolve = True
+
+            if resolve and not key.startswith('_'):
+                try:
+                    # value = attrgetter(key)(self._obj)
+                    value = Variable(key).resolve(self._obj)
+                    # TODO: Variable(key) __init__ is actually slower than
+                    #       Variable.resolve - so it better be cached
+                except VariableDoesNotExist as e:
+                    raise AttributeError(key) from e
         return self._convert_result(value)
 
     # def get(self, key: Any, default: Any = None) -> Any:

tests/test_schema.py

@@ -68,6 +68,11 @@ class UserSchema(Schema):
     avatar: Optional[str] = None
 
 
+class BossSchema(Schema):
+    name: str
+    title: str
+
+
 class UserWithBossSchema(UserSchema):
     boss: Optional[str] = Field(None, alias="boss.name")
     has_boss: bool
@@ -78,6 +83,11 @@ def resolve_has_boss(obj):
         return bool(obj.boss)
 
 
+class NestedUserWithBossSchema(UserSchema):
+    boss: Optional[BossSchema] = None
+    boss_name: Optional[str] = Field(None, alias="boss.name")
+
+
 class UserWithInitialsSchema(UserWithBossSchema):
     initials: str
 
@@ -144,6 +154,19 @@ def test_with_boss_schema():
     }
 
 
+def test_boss_schema_as_nested_dict():
+    user = User()
+    schema = NestedUserWithBossSchema.from_orm(user)
+
+    result1 = schema.dict(by_alias=True)
+    result1_no_boss_name = result1.copy()
+    result1_no_boss_name.pop('boss.name')
+
+    result2 = NestedUserWithBossSchema.from_orm(result1_no_boss_name).dict(by_alias=True)
+
+    assert result1 == result2
+
+
 SKIP_NON_STATIC_RESOLVES = True