flesh out protocol impl (#306)

refining protocols introduced in #296 for the refactor described in #167

* renamed DimensionRegistry → DimensionResolver
* renamed DimensionRegistryMixin → DimensionResolverMixin
* renamed get_dimensions() → get_dims()
* consolidated resolve_dimension() / get_all_dimensions() → resolve_dims()
* resolve_dims() accepts multiple (or no) dim names and returns dict for consistency:
    * resolve_dims() → all available dimensions
    * resolve_dims('nlay') → {'nlay': 3}
    * resolve_dims('nlay', 'nrow') → {'nlay': 3, 'nrow': 10}

Author: wpbonelli

docs/dev/protocols-plan.md

@@ -127,25 +127,39 @@ For development/testing, provide an optional validation function:
   - Caching tests
   - All tests passing
 
-### Phase 3: Not Started
-
-  **Integrate with _resolve_dimensions** - NOT DONE
-  - Update _resolve_dimensions() in structure.py:
-    - Try parent.get_all_dimensions() FIRST (new path)
-    - Fall back to xattree's parent.data.dims (compatibility)
-    - Keep computed dimension fallback (temporary)
-  - All tests pass using both new and fallback paths
-  - Tests: All existing tests pass (proving coexistence works)
-
-  NOTE: structure.py has been created but still uses old xattree path (parent.data.dims)
-
-  **Validation** - NOT DONE
-  - Add conflict detection in get_all_dimensions()
-  - Add optional validate_dimension_resolution() tool
+### Phase 3: Complete ✅
+
+  **Integrate with _resolve_dimensions** - DONE ✅
+  - Updated _resolve_dimensions() in structure.py:
+    - Uses parent.resolve_dims() (new path)
+    - Removed xattree fallback - cleaner, simpler code
+  - Updated resolve_dims() to include parent dimensions (walks up hierarchy)
+  - Tests: All 207 non-integration tests pass
+
+  **Validation** - DONE ✅
+  - Added conflict detection in resolve_dims()
+    - Detects conflicts among children at same level
+    - Allows children to override parent dimensions
+  - Added validate_dimension_resolution() validation tool in dimensions.py
+
+  **Implement Disv DimensionProvider** - DONE ✅
+  - Added get_dims() to Disv class
+  - Returns nlay, ncpl, nvert, and computed nodes dimension
+  - All Disv-related tests now pass
+
+  **API Refinements** - DONE ✅
+  - Renamed: DimensionRegistry → DimensionResolver
+  - Renamed: DimensionRegistryMixin → DimensionResolverMixin
+  - Renamed: get_dimensions() → get_dims()
+  - Unified API: resolve_dimension() + get_all_dimensions() → resolve_dims()
+  - resolve_dims() always returns dict for consistency:
+    - `resolve_dims()` → all available dimensions
+    - `resolve_dims('nlay')` → `{'nlay': 3}`
+    - `resolve_dims('nlay', 'nrow')` → `{'nlay': 3, 'nrow': 10}`
 
   **ParentSettingDict** - NOT DONE
   - Not yet implemented
-  - Planned for Phase 3 (parent management migration)
+  - Deferred to Phase 4 (parent management migration)
 
 ### Phase 4: Future Work
 

flopy4/mf6/component.py

@@ -9,7 +9,7 @@
 from xattree import xattree
 
 from flopy4.mf6.constants import MF6
-from flopy4.mf6.dimensions import DimensionRegistryMixin
+from flopy4.mf6.dimensions import DimensionResolverMixin
 from flopy4.mf6.spec import field, fields_dict
 from flopy4.mf6.utils.grid import update_maxbound
 from flopy4.mf6.write_context import WriteContext
@@ -22,7 +22,7 @@
 # kw_only=True necessary so we can define optional fields here
 # and required fields in subclasses. attrs complains otherwise
 @xattree(kw_only=True)
-class Component(DimensionRegistryMixin, ABC, MutableMapping):
+class Component(DimensionResolverMixin, ABC, MutableMapping):
     """
     Base class for MF6 components.
 

flopy4/mf6/converter/ingress/structure.py

@@ -10,6 +10,7 @@
 from flopy4.adapters import get_nn
 from flopy4.mf6.config import SPARSE_THRESHOLD
 from flopy4.mf6.constants import FILL_DNODATA
+from flopy4.mf6.dimensions import DimensionResolver
 
 
 def structure_keyword(value, field) -> str | None:
@@ -48,7 +49,10 @@ def _resolve_dimensions(
 
     # Resolve dims from model context
     # Priority: 1) explicit dims parameter, 2) self_.__dict__, 3) parent
-    inherited_dims = dict(self_.parent.data.dims) if self_.parent else {}
+    inherited_dims = {}
+    if self_.parent and isinstance(self_.parent, DimensionResolver):
+        inherited_dims = self_.parent.resolve_dims()
+
     explicit_dims = self_.__dict__.get("dims", {})
     dim_dict = inherited_dims | explicit_dims