Merge pull request #164 from jacebrowning/hotfix/v0.8.1

Fix loading of missing nested dataclass attributes

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.8.1 (2020-03-30)
+
+- Fixed loading of `Missing` nested dataclasses attributes.
+
 # 0.8 (2020-03-28)
 
 - Updated the `@datafile(...)` decorator to be used as a drop-in replacement for `@dataclass(...)`.

datafiles/converters/containers.py

@@ -159,7 +159,7 @@ def to_python_value(cls, deserialized_data, *, target_object):
 
         new_value = cls.DATACLASS(**data)  # pylint: disable=not-callable
 
-        if target_object is None:
+        if target_object is None or target_object is Missing:
             value = new_value
         else:
             value = target_object

pyproject.toml

@@ -1,7 +1,7 @@
 [tool.poetry]
 
 name = "datafiles"
-version = "0.8"
+version = "0.8.1"
 description = "File-based ORM for dataclasses."
 
 license = "MIT"

tests/test_instantiation.py

@@ -4,8 +4,8 @@
 
 from dataclasses import dataclass, field
 
-from datafiles import datafile
-from datafiles.utils import write
+from datafiles import Missing, datafile
+from datafiles.utils import logbreak, write
 
 
 @datafile('../tmp/sample.yml', manual=True)
@@ -171,3 +171,26 @@ def when_file_exists(expect):
         expect(sample.a) == 1.2
         expect(sample.b) == 3.4
         expect(sample.c) == 9.9
+
+
+def describe_missing_attributes():
+    def when_dataclass(expect):
+        @dataclass
+        class Name:
+            value: str
+
+        @datafile("../tmp/samples/{self.key}.yml")
+        @dataclass
+        class Sample:
+
+            key: int
+            name: Name
+            value: float = 0.0
+
+        sample = Sample(42, Name("Widget"))
+
+        logbreak("Loading missing 'name' dataclass")
+
+        sample2 = Sample(42, Missing)  # type: ignore
+
+        expect(sample2.name.value) == "Widget"