use Dfn.from_dict, misc cleanup

flopy4/mf6/component.py

@@ -9,7 +9,7 @@
 from packaging.version import Version
 from xattree import xattree
 
-from flopy4.mf6.constants import FILL_DNODATA
+from flopy4.mf6.constants import FILL_DNODATA, MF6
 from flopy4.mf6.spec import field, fields_dict, to_field
 from flopy4.uio import IO, Loader, Writer
 
@@ -84,9 +84,8 @@ class Component(ABC, MutableMapping):
     _load = IO(Loader)  # type: ignore
     _write = IO(Writer)  # type: ignore
 
-    filename: str | None = field(default=None)
-
     dfn: ClassVar[Dfn]
+    filename: str | None = field(default=None)
 
     @property
     def path(self) -> Path:
@@ -180,19 +179,19 @@ def get_dfn(cls) -> Dfn:
             blocks=blocks,
         )
 
-    def _preio(self, format: str) -> None:
+    def _preio(self, format: str = MF6) -> None:
         # prep for io operations
         if not self.filename:
             self.filename = self.default_filename()
 
-    def load(self, format: str) -> None:
+    def load(self, format: str = MF6) -> None:
         """Load the component and any children."""
         self._preio(format=format)
         self._load(format=format)
         for child in self.children.values():  # type: ignore
             child.load(format=format)
 
-    def write(self, format: str) -> None:
+    def write(self, format: str = MF6) -> None:
         """Write the component and any children."""
         self._preio(format=format)
         self._write(format=format)

flopy4/uio.py

@@ -57,7 +57,7 @@ def register_writer(self, cls, format, function):
 
     def load(self, cls, instance, *args, format=None, **kwargs):
         _load = self.get_loader(cls, format)
-        _load(instance, *args, **kwargs)
+        return _load(instance, *args, **kwargs)
 
     def write(self, cls, instance, *args, format=None, **kwargs):
         _write = self.get_writer(cls, format)
@@ -71,14 +71,17 @@ def write(self, cls, instance, *args, format=None, **kwargs):
 
 
 class IO(property):
-    """Wrap a file IO descriptor as a property."""
+    """
+    Custom property wrapper for IO operation descriptors.
+    See the `astropy` source for more details/motivation.
+    """
 
     def __get__(self, instance, owner_cls):
         return self.fget(instance, owner_cls)
 
 
 class IODescriptor:
-    """Base class for file IO operations, implemented as descriptors."""
+    """Base class for file IO operation descriptors."""
 
     def __init__(self, instance, cls, op: Op, registry: Registry | None = None):
         self._registry = registry or DEFAULT_REGISTRY
@@ -107,7 +110,7 @@ class Loader(IODescriptor):
     def __init__(self, instance, cls):
         super().__init__(instance, cls, "load", registry=DEFAULT_REGISTRY)
 
-    def __call__(self, *args, **kwargs) -> None:
+    def __call__(self, *args, **kwargs):
         return self.registry.load(self._cls, self._instance, *args, **kwargs)
 
 
@@ -118,4 +121,4 @@ def __init__(self, instance, cls):
         super().__init__(instance, cls, "write", registry=DEFAULT_REGISTRY)
 
     def __call__(self, *args, **kwargs) -> None:
-        return self.registry.write(self._cls, self._instance, *args, **kwargs)
+        self.registry.write(self._cls, self._instance, *args, **kwargs)