[field] Deprecate Field subclasses

phi/field/_field.py

@@ -1,3 +1,4 @@
+import inspect
 import warnings
 from numbers import Number
 from typing import TypeVar, Callable, Union
@@ -152,6 +153,14 @@ def is_staggered(self):
         from ._grid import StaggeredGrid
         return isinstance(self, StaggeredGrid)
 
+    @property
+    def is_centered(self):
+        return not self.is_staggered
+
+    @property
+    def sampled_at(self):
+        return 'face' if self.is_staggered else 'center'
+
 
 class SampledField(Field):
     """
@@ -481,3 +490,27 @@ def as_extrapolation(obj: Union[Extrapolation, float, Field, None]) -> Extrapola
         return FieldEmbedding(obj)
     else:
         return math.extrapolation.as_extrapolation(obj)
+
+
+def deprecated_field_class(for_class: str, parent_metaclass=None, allowed=("/phi/field/_field_math.py", "/phi/field/_grid.py")):
+    class _WarnOnInstanceChecks(parent_metaclass or type):
+
+        def __instancecheck__(self, instance):
+            caller_frame = inspect.currentframe().f_back
+            caller_code = caller_frame.f_code
+            caller_file = caller_code.co_filename
+            for filename in allowed:
+                if filename in caller_file:
+                    break
+            else:
+                warnings.warn(f"Instance checks on {for_class} are deprecated and will be removed in version 3.0. Use the methods instance.is_grid, instance.is_point_cloud, instance.is_centered and instance.is_staggered instead.", FutureWarning, stacklevel=2)
+            return type.__instancecheck__(self, instance)
+
+        def __subclasscheck__(self, subclass):
+            warnings.warn(f"Subclass checks on {for_class} are deprecated and will be removed in version 3.0", FutureWarning, stacklevel=2)
+            return type.__subclasscheck__(self, subclass)
+
+    return _WarnOnInstanceChecks
+
+
+# warnings.simplefilter('always', DeprecationWarning)

phi/field/_grid.py

@@ -5,7 +5,7 @@
 from phi import math, geom
 from phi.geom import Box, Geometry, GridCell
 from ._embed import FieldEmbedding
-from ._field import SampledField, Field, sample, reduce_sample, as_extrapolation
+from ._field import SampledField, Field, sample, reduce_sample, as_extrapolation, deprecated_field_class
 from ..geom._stack import GeometryStack
 from phiml.math import Shape, NUMPY
 from phiml.math._shape import spatial, channel, parse_dim_order
@@ -14,7 +14,7 @@
 from phiml.math.magic import slicing_dict
 
 
-class Grid(SampledField):
+class Grid(SampledField, metaclass=deprecated_field_class('Grid')):
     """
     Base class for `CenteredGrid` and `StaggeredGrid`.
     """
@@ -144,7 +144,7 @@ def uniform_values(self):
 GridType = TypeVar('GridType', bound=Grid)
 
 
-class CenteredGrid(Grid):
+class CenteredGrid(Grid, metaclass=deprecated_field_class('CenteredGrid', parent_metaclass=type(Grid))):
     """
     N-dimensional grid with values sampled at the cell centers.
     A centered grid is defined through its `CenteredGrid.values` `phiml.math.Tensor`, its `CenteredGrid.bounds` `phi.geom.Box` describing the physical size, and its `CenteredGrid.extrapolation` (`phiml.math.extrapolation.Extrapolation`).
@@ -282,7 +282,7 @@ def closest_values(self, points: Geometry):
         return math.closest_grid_values(self.values, local_points, self.extrapolation)
 
 
-class StaggeredGrid(Grid):
+class StaggeredGrid(Grid, metaclass=deprecated_field_class('StaggeredGrid', parent_metaclass=type(Grid))):
     """
     N-dimensional grid whose vector components are sampled at the respective face centers.
     A staggered grid is defined through its values tensor, its bounds describing the physical size, and its extrapolation.

phi/field/_point_cloud.py

@@ -5,15 +5,15 @@
 
 from phi import math
 from phi.geom import Geometry, GridCell, Box, Point
-from ._field import SampledField, resample
+from ._field import SampledField, resample, deprecated_field_class
 from ..geom._stack import GeometryStack
 from phiml.math import Tensor, instance, Shape
 from phiml.math._tensors import may_vary_along
 from phiml.math.extrapolation import Extrapolation, ConstantExtrapolation, PERIODIC
 from phiml.math.magic import slicing_dict
 
 
-class PointCloud(SampledField):
+class PointCloud(SampledField, metaclass=deprecated_field_class('PointCloud')):
     """
     A `PointCloud` comprises: