Updated grid implementation

tests/test_grid.py

@@ -1,21 +1,6 @@
 """Test module for grid.py.
 
-NAME
-test_grid.py
-
-DESCRIPTION
-This module tests the following functions from grid.py:
-
-- grid.make_square_grid
-    Create a square grid.
-
-- grid.make_hex_grid
-    Create a hexagonal grid.
-
-- TODO The grid.Grid class.
-
-- TODO grid.Grid.dump and grid.Grid.dumps for0 geojson
-
+This module tests the functionality of grid.py
 """
 
 import json
@@ -88,6 +73,36 @@ def test_make_hex_grid(cell_id):
     assert np.rad2deg(rad) == pytest.approx(60)
 
 
+@pytest.mark.parametrize(
+    argnames=["grid_type", "excep_type", "message"],
+    argvalues=[
+        ("penrose", ValueError, "The grid_type penrose is not defined."),
+        (
+            "square",
+            ValueError,
+            "The square creator function generated ids and polygons of unequal length.",
+        ),
+    ],
+)
+def test_grid_exceptions(mocker, grid_type, excep_type, message):
+    """Test Grid init exceptions."""
+
+    from virtual_rainforest.core.grid import Grid
+
+    # Mock the registered 'square' creator with something that returns unequal length
+    # ids and polygons tuples.
+    mocker.patch.dict(
+        "virtual_rainforest.core.grid.GRID_REGISTRY",
+        {"square": lambda *args, **kwargs: ((1, 2, 3, 4), ("poly", "poly", "poly"))},
+    )
+
+    with pytest.raises(excep_type) as err:
+
+        Grid(grid_type=grid_type)
+
+    assert str(err.value) == message
+
+
 @pytest.mark.parametrize(argnames=["preset_distances"], argvalues=[(True,), (False,)])
 @pytest.mark.parametrize(
     argnames=["grid_type", "cfrom", "cto"],

virtual_rainforest/core/grid.py

@@ -13,7 +13,7 @@
 """
 
 import json
-from typing import Any, Callable, NamedTuple, Optional, Sequence, Union
+from typing import Any, Callable, Optional, Sequence, Union
 
 import numpy as np
 import numpy.typing as npt
@@ -31,23 +31,16 @@
 decorator.
 """
 
-
-class GridStructure(NamedTuple):
-    """Data structure to be returned from grid creator functions.
-
-    The contents should be two equal length lists giving unique integer ID values
-    and corresponding shapely.geometry.Polygon objects.
-    """
-
-    ids: list[int]
-    polygons: list[Polygon]
+GRID_STRUCTURE_SIG = tuple[tuple[int, ...], tuple[Polygon, ...]]
+"""Signature of the data structure to be returned from grid creator functions."""
 
 
 def register_grid(grid_type: str) -> Callable:
     """Add a grid type and creator function to the grid registry.
 
     This decorator is used to add a function creating a grid layout to the registry of
-    accepted grids and returning an object of class GridStructure.
+    accepted grids. The function must return equal-length tuples of integer polygon ids
+    and Polygon objects, following the GRID_STRUCTURE_SIG signature.
 
     The grid_type argument is used to identify the grid creation function to be used by
     the Grid class and in configuration files.
@@ -77,7 +70,7 @@ def make_square_grid(
     cell_ny: int,
     xoff: float = 0,
     yoff: float = 0,
-) -> GridStructure:
+) -> GRID_STRUCTURE_SIG:
     """Create a square grid.
 
     Args:
@@ -88,7 +81,7 @@ def make_square_grid(
         yoff: An offset to use for the grid origin in the Y direction.
 
     Returns:
-        A GridStructure instance
+        Equal-length tuples of integer polygon ids and Polygon objects
     """
 
     # Create the polygon prototype object, with origin at 0,0 and area 1
@@ -113,7 +106,7 @@ def make_square_grid(
                 prototype, xoff=scale_factor * x_idx, yoff=scale_factor * y_idx
             )
 
-    return GridStructure(ids=list(range(len(cell_list))), polygons=cell_list)
+    return (tuple(range(len(cell_list))), tuple(cell_list))
 
 
 @register_grid(grid_type="hexagon")
@@ -123,7 +116,7 @@ def make_hex_grid(
     cell_ny: int,
     xoff: float = 0,
     yoff: float = 0,
-) -> GridStructure:
+) -> GRID_STRUCTURE_SIG:
     """Create a hexagonal grid.
 
     Args:
@@ -134,7 +127,7 @@ def make_hex_grid(
         yoff: An offset to use for the grid origin in the Y direction.
 
     Returns:
-        A GridStructure instance
+        Equal-length tuples of integer polygon ids and Polygon objects
     """
 
     # TODO - implement grid orientation and kwargs passing
@@ -179,7 +172,7 @@ def make_hex_grid(
                 yoff=1.5 * side_length * y_idx,
             )
 
-    return GridStructure(ids=list(range(len(cell_list))), polygons=cell_list)
+    return (tuple(range(len(cell_list))), tuple(cell_list))
 
 
 @register_grid(grid_type="triangle")
@@ -189,7 +182,7 @@ def make_triangular_grid(
     cell_ny: int,
     xoff: float = 0,
     yoff: float = 0,
-) -> GridStructure:
+) -> GRID_STRUCTURE_SIG:
     """Create a equilateral triangular grid.
 
     Args:
@@ -258,16 +251,20 @@ def __init__(
             raise ValueError(f"The grid_type {self.grid_type} is not defined.")
 
         # Run the grid creation
-        grid_structure = creator(
+        self.cell_id, self.polygons = creator(
             cell_area=self.cell_area,
             cell_nx=self.cell_nx,
             cell_ny=self.cell_ny,
             xoff=self.xoff,
             yoff=self.yoff,
         )
 
-        self.cell_id = grid_structure.ids
-        self.polygons = grid_structure.polygons
+        if len(self.cell_id) != len(self.polygons):
+            raise ValueError(
+                f"The {self.grid_type} creator function generated ids and polygons of "
+                "unequal length."
+            )
+
         self.n_cells = len(self.cell_id)
 
         # Get the centroids as a numpy array