BUG: Disown Python objects adopted by unique_ptr members

GradientImageFilter::OverrideBoundaryCondition and
OptimizerParameters::SetHelper store their raw-pointer argument in a
unique_ptr member, but the Python wrapping left ownership with the proxy.
Both sides freed the object and the interpreter aborted at shutdown.

Apply SWIGTYPE *DISOWN to both parameters and add Python regression tests.

Author: hjmjohnson

Modules/Core/Common/wrapping/itkOptimizerParameters.wrap

@@ -7,6 +7,9 @@ itk_end_wrap_class()
 
 itk_wrap_class("itk::OptimizerParameters")
 foreach(t ${types})
+  # SetHelper stores the argument in a unique_ptr member.
+  string(APPEND ITK_WRAP_PYTHON_SWIG_EXT "%apply SWIGTYPE *DISOWN { itkOptimizerParametersHelper${ITKM_${t}} * helper };\n")
+
   itk_wrap_template("${ITKM_${t}}" "${ITKT_${t}}")
 endforeach()
 itk_end_wrap_class()

Modules/Core/Common/wrapping/test/CMakeLists.txt

@@ -66,4 +66,9 @@ if(ITK_WRAP_PYTHON)
     COMMAND
       ${CMAKE_CURRENT_SOURCE_DIR}/itkImageLifetimeTest.py
   )
+  itk_python_add_test(
+    NAME itkOptimizerParametersOwnershipPythonTest
+    COMMAND
+      ${CMAKE_CURRENT_SOURCE_DIR}/itkOptimizerParametersOwnershipTest.py
+  )
 endif()

Modules/Core/Common/wrapping/test/itkOptimizerParametersOwnershipTest.py

@@ -0,0 +1,36 @@
+# ==========================================================================
+#
+#   Copyright NumFOCUS
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#          https://www.apache.org/licenses/LICENSE-2.0.txt
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+#
+# ==========================================================================
+"""OptimizerParameters.SetHelper takes ownership of its argument.
+
+Without a DISOWN typemap, Python and the m_Helper unique_ptr both free the helper,
+and the interpreter aborts at shutdown.  A non-zero exit code from this script is
+itself part of the regression check.
+"""
+
+import itk
+
+parameters = itk.OptimizerParameters[itk.D](3)
+helper = itk.OptimizerParametersHelper[itk.D]()
+
+assert helper.thisown, "Python should own a freshly constructed helper"
+
+parameters.SetHelper(helper)
+
+assert not helper.thisown, "SetHelper must transfer ownership away from Python"
+
+print("Test finished.")

Modules/Filtering/ImageGradient/wrapping/itkGradientImageFilter.wrap

@@ -4,6 +4,13 @@ foreach(d ${ITK_WRAP_IMAGE_DIMS})
   set(vector_dim ${d}) # Wrap only vector dimensions which are the same as image dimensions
   foreach(t ${WRAP_ITK_SCALAR})
 
+    # OverrideBoundaryCondition stores the argument in a unique_ptr member.
+    string(
+      APPEND
+      ITK_WRAP_PYTHON_SWIG_EXT
+      "%apply SWIGTYPE *DISOWN { itkImageBoundaryCondition${ITKM_I${t}${vector_dim}} * boundaryCondition };\n"
+    )
+
     if(ITK_WRAP_covariant_vector_float)
       itk_wrap_template("${ITKM_I${t}${vector_dim}}${ITKM_F}${ITKM_F}" "${ITKT_I${t}${vector_dim}},${ITKT_F},${ITKT_F}")
     endif()

Modules/Filtering/ImageGradient/wrapping/test/CMakeLists.txt

@@ -14,4 +14,10 @@ if(ITK_WRAP_PYTHON AND ITK_WRAP_float AND wrap_2_index GREATER -1)
       ${ITK_TEST_OUTPUT_DIR}/GradientMagnitudeRecursiveGaussianImageFilterTest.png
       5
   )
+
+  itk_python_add_test(
+    NAME itkGradientImageFilterOwnershipPythonTest
+    COMMAND
+      ${CMAKE_CURRENT_SOURCE_DIR}/itkGradientImageFilterOwnershipTest.py
+  )
 endif()

Modules/Filtering/ImageGradient/wrapping/test/itkGradientImageFilterOwnershipTest.py

@@ -0,0 +1,57 @@
+# ==========================================================================
+#
+#   Copyright NumFOCUS
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#          https://www.apache.org/licenses/LICENSE-2.0.txt
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+#
+# ==========================================================================
+"""GradientImageFilter.OverrideBoundaryCondition takes ownership of its argument.
+
+Without a DISOWN typemap, Python and the filter's unique_ptr member both free the
+boundary condition, and the interpreter aborts at shutdown.  A non-zero exit code
+from this script is itself part of the regression check.
+"""
+
+import itk
+
+itk.auto_progress(2)
+
+ImageType = itk.Image[itk.F, 2]
+
+filt = itk.GradientImageFilter[ImageType, itk.F, itk.F].New()
+boundaryCondition = itk.PeriodicBoundaryCondition[ImageType]()
+
+assert (
+    boundaryCondition.thisown
+), "Python should own a freshly constructed boundary condition"
+
+filt.OverrideBoundaryCondition(boundaryCondition)
+
+assert (
+    not boundaryCondition.thisown
+), "OverrideBoundaryCondition must transfer ownership away from Python"
+
+# The filter must remain usable with the adopted boundary condition.
+image = ImageType.New()
+region = itk.ImageRegion[2]()
+region.SetSize([8, 8])
+image.SetRegions(region)
+image.Allocate()
+image.FillBuffer(1.0)
+
+filt.SetInput(image)
+filt.Update()
+
+assert filt.GetOutput().GetLargestPossibleRegion().GetSize()[0] == 8
+
+print("Test finished.")