Fixing alignment side effect

HISTORY.rst

@@ -16,6 +16,10 @@ Unreleased Changes
 * Updating pyproject.toml to use the standard ``license-files`` key and
   replacing the license-related Trove classifier with the approved SPDX string.
   https://github.com/natcap/pygeoprocessing/issues/466
+* Fixing a side effect in ``pygeoprocessing.align_and_resize_raster_stack``
+  where aligning a raster stack using the bounding box mode would result in the
+  input bounding box being modified in-place.
+  https://github.com/natcap/pygeoprocessing/issues/471
 
 2.4.10 (2026-01-13)
 -------------------

src/pygeoprocessing/geoprocessing.py

@@ -1084,6 +1084,9 @@ def align_and_resize_raster_stack(
             [target_bounding_box, mask_vector_bb], 'intersection')
 
     if raster_align_index is not None and raster_align_index >= 0:
+        # ensure we are working with a copy of the bounding box so that the
+        # original is unmodified.
+        target_bounding_box = target_bounding_box[:]
         # bounding box needs alignment
         align_bounding_box = (
             raster_info_list[raster_align_index]['bounding_box'])

tests/test_geoprocessing.py

@@ -2551,17 +2551,39 @@ def test_align_and_resize_raster_stack_bb(self):
         # goes first in the following bounding box construction
         base_a_raster_info = pygeoprocessing.get_raster_info(base_a_path)
 
+        # Make a new bounding box that's in between the two and not perfectly
+        # aligned to the pixels in base_a_raster.
+        xmin, ymin, xmax, ymax = base_a_raster_info['bounding_box']
+        target_bbox = [
+            xmin+23,
+            ymin+23,
+            xmax-46,
+            ymax-46,
+        ]
+
+        # REGRESSION TEST: make sure this input variable is unmodified after
+        # execution
+        # https://github.com/natcap/pygeoprocessing/issues/471
+        target_bbox_copy = target_bbox[:]
+
         pygeoprocessing.align_and_resize_raster_stack(
             base_raster_path_list, target_raster_path_list,
             resample_method_list,
-            base_a_raster_info['pixel_size'], 'intersection',
+            base_a_raster_info['pixel_size'],
+            target_bbox,
             base_vector_path_list=None, raster_align_index=0)
 
+        # REGRESSION TEST: make sure this input variable is unmodified after
+        # execution.
+        # https://github.com/natcap/pygeoprocessing/issues/471
+        self.assertEqual(target_bbox, target_bbox_copy)
+
         # we expect this to be twice as big since second base raster has a
         # pixel size twice that of the first.
         target_array = pygeoprocessing.raster_to_numpy_array(
             target_raster_path_list[0])
-        numpy.testing.assert_array_equal(pixel_a_matrix, target_array)
+        numpy.testing.assert_array_equal(
+            numpy.ones((4, 4), pixel_a_matrix.dtype), target_array)
 
     def test_raster_calculator(self):
         """PGP.geoprocessing: raster_calculator identity test."""