model: handle copying embedded model collections

Find all instances of _BaseODMModel subclasses, including those stored
in lists or tuples, and set the required attribute on them during copy.

Fixes art049#321.

odmantic/model.py

@@ -1,6 +1,7 @@
 import datetime
 import decimal
 import enum
+import functools
 import pathlib
 import uuid
 import warnings
@@ -16,6 +17,7 @@
     FrozenSet,
     Iterable,
     List,
+    NamedTuple,
     Optional,
     Set,
     Tuple,
@@ -499,6 +501,29 @@ def __new__(
 
 
 BaseT = TypeVar("BaseT", bound="_BaseODMModel")
+TraversalStateT = NamedTuple(
+    "TraversalStateT", [("output", List[Any]), ("staging", List[Any])]
+)
+
+
+def flat_tree(o: BaseT) -> List[BaseT]:
+    state = TraversalStateT(output=[], staging=[o])
+
+    def obj_fields(obj):
+        return [getattr(obj, name) for name in set(obj.__odm_fields__)]
+
+    def unpack(acc: TraversalStateT, obj: Any) -> TraversalStateT:
+        output, (_, *staging_tail) = acc
+        if isinstance(obj, _BaseODMModel):
+            return TraversalStateT(output + [obj], staging_tail + obj_fields(obj))
+        elif isinstance(obj, Iterable) and not isinstance(obj, (str, dict)):
+            return TraversalStateT(output, staging_tail + [*obj])
+        else:
+            return TraversalStateT(output, staging_tail)
+
+    while state.staging:
+        state = functools.reduce(unpack, state.staging, state)
+    return state.output
 
 
 class _BaseODMModel(pydantic.BaseModel, metaclass=ABCMeta):
@@ -583,11 +608,8 @@ def _post_copy_update(self: BaseT) -> None:
         """Recursively update internal fields of the copied model after it has been
         copied.
         """
-        object.__setattr__(self, "__fields_modified__", set(self.__fields__))
-        for field_name, field in self.__odm_fields__.items():
-            if isinstance(field, ODMEmbedded):
-                value = getattr(self, field_name)
-                value._post_copy_update()
+        for model in flat_tree(self):
+            object.__setattr__(model, "__fields_modified__", set(model.__fields__))
 
     def update(
         self,

tests/unit/test_model_logic.py

@@ -389,6 +389,27 @@ class M(Model):
     assert instance.e.f.g != copied.e.f.g
 
 
+@pytest.mark.parametrize(
+    "hint, ctor",
+    [
+        pytest.param(List, list),
+        pytest.param(Tuple, tuple),
+    ],
+)
+def test_model_copy_deep_embedded_model_collection(hint, ctor):
+    class E(EmbeddedModel):
+        f: int
+
+    class M(Model):
+        e: hint[E]
+
+    instance = M(e=ctor([E(f=1)]))
+    copied = instance.copy(deep=True)
+    copied.e[0].f = 2
+
+    assert copied.e[0].f != instance.e[0].f
+
+
 def test_model_copy_not_deep_embedded():
     class E(EmbeddedModel):
         f: int