Fix handling of default values on nested dataclasses

datafiles/converters/containers.py

@@ -1,10 +1,10 @@
 from collections.abc import Iterable
 from contextlib import suppress
-from dataclasses import _MISSING_TYPE as Missing
 from typing import Callable, Dict
 
 import log
 
+from ..utils import Missing, get_default_field_value
 from ._bases import Converter
 
 
@@ -148,7 +148,10 @@ def to_python_value(cls, deserialized_data, *, target_object):
             if name in data:
                 data[name] = converter.to_python_value(data[name], target_object=None)
             else:
-                data[name] = converter.to_python_value(None, target_object=None)
+                if target_object is None:
+                    data[name] = converter.to_python_value(None, target_object=None)
+                else:
+                    data[name] = get_default_field_value(target_object, name)
 
         new_value = cls.DATACLASS(**data)  # pylint: disable=not-callable
 

datafiles/mapper.py

@@ -13,26 +13,14 @@
 
 from . import config, formats, hooks
 from .converters import Converter, List, map_type
-from .utils import display, recursive_update, write
-
-
-Trilean = Optional[bool]
-Missing = dataclasses._MISSING_TYPE
-
-
-def get_default_field_value(instance, name):
-    for field in dataclasses.fields(instance):
-        if field.name == name:
-            if not isinstance(field.default, Missing):
-                return field.default
-
-            if not isinstance(field.default_factory, Missing):  # type: ignore
-                return field.default_factory()  # type: ignore
-
-            if not field.init and hasattr(instance, '__post_init__'):
-                return getattr(instance, name)
-
-    return Missing
+from .utils import (
+    Missing,
+    Trilean,
+    display,
+    get_default_field_value,
+    recursive_update,
+    write,
+)
 
 
 class Mapper:

datafiles/utils.py

@@ -1,18 +1,38 @@
 """Internal helper functions."""
 
+import dataclasses
 from contextlib import suppress
 from functools import lru_cache
 from pathlib import Path
 from pprint import pformat
 from shutil import get_terminal_size
-from typing import Dict, Union
+from typing import Dict, Optional, Union
 
 import log
 
 
+Trilean = Optional[bool]
+Missing = dataclasses._MISSING_TYPE
+
+
 cached = lru_cache()
 
 
+def get_default_field_value(instance, name):
+    for field in dataclasses.fields(instance):
+        if field.name == name:
+            if not isinstance(field.default, Missing):
+                return field.default
+
+            if not isinstance(field.default_factory, Missing):  # type: ignore
+                return field.default_factory()  # type: ignore
+
+            if not field.init and hasattr(instance, '__post_init__'):
+                return getattr(instance, name)
+
+    return Missing
+
+
 def prettify(value) -> str:
     """Ensure value is a dictionary pretty-format it."""
     return pformat(dictify(value))
@@ -108,4 +128,4 @@ def logbreak(message: str = "") -> None:
         line = '-' * (width - len(message) - 1) + ' ' + message
     else:
         line = '-' * width
-    log.info(line)
+    log.critical(line)

tests/test_loading.py

@@ -2,9 +2,12 @@
 
 # pylint: disable=unused-variable
 
+from dataclasses import dataclass
+
 import pytest
 
-from datafiles.utils import logbreak, write
+from datafiles import datafile
+from datafiles.utils import dedent, logbreak, read, write
 
 from .samples import (
     Sample,
@@ -230,6 +233,98 @@ def with_extra_attributes(sample, expect):
         expect(sample.nested.score) == 3.4
         expect(hasattr(sample.nested, 'extra')) == False
 
+    def with_multiple_levels(expect):
+        @dataclass
+        class Bottom:
+            level: int = 4
+
+        @dataclass
+        class C:
+            level: int = 3
+            d: Bottom = Bottom()
+
+        @dataclass
+        class B:
+            level: int = 2
+            c: C = C()
+
+        @dataclass
+        class A:
+            level: int = 1
+            b: B = B()
+
+        @datafile('../tmp/sample.toml', defaults=True, auto_save=False)
+        class Top:
+            level: int = 0
+            a: A = A()
+
+        sample = Top()
+
+        expect(read('tmp/sample.toml')) == dedent(
+            """
+            level = 0
+
+            [a]
+            level = 1
+
+            [a.b]
+            level = 2
+
+            [a.b.c]
+            level = 3
+
+            [a.b.c.d]
+            level = 4
+            """
+        )
+
+        logbreak("Modifying attribute")
+        sample.a.b.c.d.level = 99
+
+        expect(read('tmp/sample.toml')) == dedent(
+            """
+            level = 0
+
+            [a]
+            level = 1
+
+            [a.b]
+            level = 2
+
+            [a.b.c]
+            level = 3
+
+            [a.b.c.d]
+            level = 99
+            """
+        )
+
+        write(
+            'tmp/sample.toml',
+            """
+            level = 0
+
+            [a]
+            level = 10
+
+            [a.b]
+            level = 20
+
+            [a.b.c]
+            level = 30
+
+            [a.b.c.d]
+            level = 40
+            """,
+        )
+
+        logbreak("Reading attribute")
+        expect(sample.a.level) == 10
+        expect(sample.a.b.level) == 20
+        expect(sample.a.b.c.level) == 30
+
+        expect(sample.a.b.c.d.level) == 40
+
 
 def describe_lists():
     def with_matching_types(expect):

tests/test_patched_methods.py

@@ -103,7 +103,7 @@ def with_delitem(expect):
     def with_append(expect):
         sample = Sample()
 
-        logbreak("Appending to list")
+        logbreak("Appending to list: 2")
         sample.items.append(2)
 
         expect(read('tmp/sample.yml')) == dedent(
@@ -116,7 +116,7 @@ def with_append(expect):
 
         sample.datafile.load()
 
-        logbreak("Appending to list")
+        logbreak("Appending to list: 3")
         sample.items.append(3)
 
         expect(read('tmp/sample.yml')) == dedent(
@@ -128,11 +128,10 @@ def with_append(expect):
             """
         )
 
-    @pytest.mark.xfail(reason="TODO: fix this")
     def with_append_on_nested_dataclass(expect):
         sample = SampleWithNesting(1)
 
-        logbreak("Appending to nested list")
+        logbreak("Appending to nested list: 2")
         sample.nested.items.append(2)
 
         expect(read('tmp/sample.yml')) == dedent(
@@ -144,7 +143,7 @@ def with_append_on_nested_dataclass(expect):
             """
         )
 
-        logbreak("Appending to nested list")
+        logbreak("Appending to nested list: 3")
         sample.nested.items.append(3)
 
         expect(read('tmp/sample.yml')) == dedent(