Reject non-finite target_values in proximity tools

xrspatial/proximity.py

@@ -1176,6 +1176,23 @@ def _process(
 
     target_values = np.asarray(target_values)
 
+    # Reject non-finite explicit target_values. On numpy a pixel holding inf
+    # matched target_values=[inf] and ran the search, while dask/cupy mask
+    # non-finite pixels out and returned all-NaN for the same input. nan can
+    # never match a pixel anyway (nan == nan is False). Fail fast instead of
+    # producing backend-dependent output (issue #2850). A non-numeric dtype
+    # (e.g. strings) can't index a raster either, so it gets the same error
+    # rather than a downstream TypeError from np.isfinite.
+    if target_values.size and (
+        target_values.dtype.kind not in "iuf"
+        or not np.isfinite(target_values).all()
+    ):
+        raise ValueError(
+            "target_values must all be finite numbers, got {0!r}.".format(
+                target_values.tolist()
+            )
+        )
+
     if max_distance is None:
         max_distance = np.inf
 
@@ -1547,7 +1564,8 @@ def proximity(
     target_values: list
         Target pixel values to measure the distance from. If this option
         is not provided, proximity will be computed from non-zero pixel
-        values.
+        values. All entries must be finite; a non-finite value (inf or
+        nan) raises ValueError.
 
     max_distance: float, default=np.inf
         The maximum distance to search. Proximity distances greater than
@@ -1696,7 +1714,8 @@ def allocation(
     target_values : list
         Target pixel values to measure the distance from. If this option
         is not provided, allocation will be computed from non-zero pixel
-        values.
+        values. All entries must be finite; a non-finite value (inf or
+        nan) raises ValueError.
 
     max_distance: float, default=np.inf
         The maximum distance to search. Proximity distances greater than
@@ -1847,7 +1866,8 @@ def direction(
     target_values: list
         Target pixel values to measure the distance from. If this
         option is not provided, proximity will be computed from
-        non-zero pixel values.
+        non-zero pixel values. All entries must be finite; a non-finite
+        value (inf or nan) raises ValueError.
 
     max_distance: float, default=np.inf
         The maximum distance to search. Proximity distances greater than

xrspatial/tests/test_proximity.py

@@ -361,6 +361,39 @@ def test_zero_max_distance_keeps_meaning(test_raster, func):
     general_output_checks(test_raster, result)
 
 
+@pytest.mark.parametrize("backend", ['numpy', 'dask+numpy', 'cupy', 'dask+cupy'])
+@pytest.mark.parametrize("func", [proximity, allocation, direction])
+@pytest.mark.parametrize("target_values", [[np.inf], [-np.inf], [np.nan], [2, np.inf]])
+def test_non_finite_target_values_raises(test_raster, func, target_values):
+    # A non-finite target_values entry used to produce backend-dependent
+    # output: numpy matched inf pixels and returned a real grid, while
+    # dask/cupy masked non-finite pixels out and returned all-NaN for the
+    # same raster (issue #2850).  It must raise on every backend instead.
+    with pytest.raises(ValueError, match="target_values"):
+        func(test_raster, x='lon', y='lat', target_values=target_values)
+
+
+@pytest.mark.parametrize("backend", ['numpy', 'dask+numpy', 'cupy', 'dask+cupy'])
+@pytest.mark.parametrize("func", [proximity, allocation, direction])
+def test_non_numeric_target_values_raises(test_raster, func):
+    # A non-numeric target_values can't index a raster; it must raise a clear
+    # ValueError on every backend rather than a downstream TypeError (#2850).
+    with pytest.raises(ValueError, match="target_values"):
+        func(test_raster, x='lon', y='lat', target_values=['a', 'b'])
+
+
+@pytest.mark.parametrize("backend", ['numpy', 'dask+numpy', 'cupy', 'dask+cupy'])
+@pytest.mark.parametrize("func", [proximity, allocation, direction])
+def test_finite_target_values_run(test_raster, func):
+    # The raster carries an inf and a nan pixel; the default (empty
+    # target_values) path must keep ignoring them on every backend, and
+    # explicit finite targets must keep working unchanged.
+    result_default = func(test_raster, x='lon', y='lat')
+    general_output_checks(test_raster, result_default)
+    result_explicit = func(test_raster, x='lon', y='lat', target_values=[1, 3])
+    general_output_checks(test_raster, result_explicit)
+
+
 def test_proximity_distance_against_qgis(raster, qgis_proximity_distance_target_values):
     target_values, qgis_result = qgis_proximity_distance_target_values
     input_raster = create_test_raster(raster)