various (#267)

* trial an approach for records containing keywords, including converter
* dicts should map to record field type, not list
* add minimal npf writing test

Author: wpbonelli

flopy4/mf6/codec/filters.py

@@ -20,12 +20,12 @@ def field_type(value: Any) -> FieldType:
         return "double"
     if isinstance(value, str):
         return "string"
-    if isinstance(value, tuple):
+    if isinstance(value, (dict, tuple)):
         return "record"
     if isinstance(value, xr.DataArray):
         if value.dtype == "object":
             return "list"
         return "array"
-    if isinstance(value, (list, dict, xr.Dataset)):
+    if isinstance(value, (list, xr.Dataset)):
         return "list"
     raise ValueError(f"Unsupported field type: {type(value)}")

flopy4/mf6/converter/__init__.py

@@ -8,7 +8,7 @@
 
 from flopy4.mf6.component import Component
 from flopy4.mf6.context import Context
-from flopy4.mf6.converter.structure import structure_array
+from flopy4.mf6.converter.structure import structure_array, structure_keyword
 from flopy4.mf6.converter.unstructure import (
     unstructure_component,
 )
@@ -19,6 +19,7 @@
     "unstructure",
     "structure_array",
     "unstructure_array",
+    "structure_keyword",
     "COMPONENT_CONVERTER",
 ]
 

flopy4/mf6/converter/structure.py

@@ -10,6 +10,10 @@
 from flopy4.mf6.constants import FILL_DNODATA
 
 
+def structure_keyword(value, field) -> str | None:
+    return field.name if value else None
+
+
 def structure_array(value, self_, field) -> NDArray:
     """
     Convert a sparse dictionary representation of an array to a

flopy4/mf6/gwf/npf.py

@@ -1,12 +1,13 @@
 from pathlib import Path
-from typing import Optional
+from typing import Literal, Optional
 
+import attrs
 import numpy as np
 from attrs import Converter, define
 from numpy.typing import NDArray
 from xattree import xattree
 
-from flopy4.mf6.converter import structure_array
+from flopy4.mf6.converter import structure_array, structure_keyword
 from flopy4.mf6.package import Package
 from flopy4.mf6.spec import array, field, path
 from flopy4.utils import to_path
@@ -16,8 +17,12 @@
 class Npf(Package):
     @define(slots=False)
     class CvOptions:
-        variablecv: bool = field(default=False)
-        dewatered: bool = field(default=False)
+        variablecv: Literal["variablecv"] = attrs.field(init=False, default="variablecv")
+        dewatered: Literal["dewatered"] | None = attrs.field(
+            default=None,
+            # TODO: adopt this pattern for all record types in all components?
+            converter=Converter(structure_keyword, takes_field=True),  # type: ignore
+        )
 
     @define(slots=False)
     class RewetRecord: