Use Python3::Interpreter instead of Python3_EXECUTABLE

The target Python3::Interpreter expands to Pyhton3_EXECUTABLE when invoked in a command context in custom targets. However, dune modules are called from a super directory, the Python3_EXECUTABLE will not be present for other modules whereas the target will be globally available if CMAKE_FIND_PACKAGE_TARGETS_GLOBAL is set to TRUE.

cmake/modules/DunePythonFindPackage.cmake

@@ -39,8 +39,8 @@
 #       :single:
 #
 #       The python interpreter, whose paths are searched for the package.
-#       Defaults to :code:`${Python3_EXECUTABLE}`, might differ when dealing with
-#       the configure-time virtualenv set up with :ref:`DUNE_PYTHON_VIRTUALENV_SETUP`.
+#       Defaults to the location of :code:`Python3::Interpreter`, which might differ when
+#       dealing with the configure-time virtualenv set up with :ref:`DUNE_PYTHON_VIRTUALENV_SETUP`.
 #
 #    Find a given python package on the system.
 #
@@ -60,14 +60,24 @@ function(dune_python_find_package)
     set(PYPACKAGE_RESULT DUNE_PYTHON_${PYPACKAGE_PACKAGE}_FOUND)
   endif()
   if(NOT PYPACKAGE_INTERPRETER)
-    set(PYPACKAGE_INTERPRETER "${Python3_EXECUTABLE}")
+    set(PYPACKAGE_INTERPRETER Python3::Interpreter)
   endif()
   if(PYPACKAGE_EXACT AND NOT PYPACKAGE_VERSION)
     message(FATAL_ERROR "dune_python_find_package: EXACT given, but no VERSION specified.")
   endif()
 
+  # Find interpreter path location
+  set(PYPACKAGE_LOCATION ${PYPACKAGE_INTERPRETER})
+  if(TARGET ${PYPACKAGE_INTERPRETER})
+    get_target_property(PYPACKAGE_LOCATION ${PYPACKAGE_INTERPRETER} LOCATION)
+  endif()
+  # sanity check on the interpreter
+  if(NOT IS_EXECUTABLE ${PYPACKAGE_LOCATION})
+    message(FATAL_ERROR "The location of the python interpreter '${PYPACKAGE_LOCATION}' is not executable")
+  endif()
+
   # Do the actual check
-  execute_process(COMMAND "${PYPACKAGE_INTERPRETER}" -c "import ${PYPACKAGE_PACKAGE}"
+  execute_process(COMMAND "${PYPACKAGE_LOCATION}" -c "import ${PYPACKAGE_PACKAGE}"
                   RESULT_VARIABLE PYPACKAGE_RETURN
                   ERROR_QUIET)
 
@@ -82,7 +92,7 @@ function(dune_python_find_package)
     # We cannot use find_package_handle_standard_args for that, as it is too
     # closely tied to using find_package(), which we cannot use for variable package
     # name...
-    execute_process(COMMAND "${PYPACKAGE_INTERPRETER}" "${scriptdir}/pyversion.py" "${PYPACKAGE_PACKAGE}"
+    execute_process(COMMAND "${PYPACKAGE_LOCATION}" "${scriptdir}/pyversion.py" "${PYPACKAGE_PACKAGE}"
                     RESULT_VARIABLE retcode
                     OUTPUT_VARIABLE VERSION_STRING
                     OUTPUT_STRIP_TRAILING_WHITESPACE
@@ -103,14 +113,14 @@ function(dune_python_find_package)
   else()
     set(${PYPACKAGE_RESULT} FALSE)
     if(PYPACKAGE_REQUIRED)
-      message(FATAL_ERROR "The python package ${PYPACKAGE_PACKAGE} could not be found! (for interpreter ${PYPACKAGE_INTERPRETER})")
+      message(FATAL_ERROR "The python package ${PYPACKAGE_PACKAGE} could not be found! (for interpreter in ${PYPACKAGE_LOCATION})")
     endif()
   endif()
 
   # Set the result variable and print the result
   include(FindPackageHandleStandardArgs)
   find_package_handle_standard_args(${PYPACKAGE_PACKAGE}_${PYPACKAGE_INTERPRETER}
-                                    "Failed to find the python package ${PYPACKAGE_PACKAGE} with interpreter ${PYPACKAGE_INTERPRETER}."
+                                    "Failed to find the python package ${PYPACKAGE_PACKAGE} with interpreter in ${PYPACKAGE_LOCATION}."
                                     ${PYPACKAGE_RESULT}
                                     )
   set(${PYPACKAGE_RESULT} ${${PYPACKAGE_RESULT}} PARENT_SCOPE)

cmake/modules/DunePythonInstallPackage.cmake

@@ -522,7 +522,7 @@ function(dune_python_configure_package)
 
     # TODO this creates an egg-info folder in the source directory
     add_custom_target(${PYPKGCONF_INSTALL_TARGET}
-                      COMMAND ${Python3_EXECUTABLE} -m pip install
+                      COMMAND Python3::Interpreter -m pip install
                         "${USER_INSTALL_OPTION}"
                        "${DUNE_PIP_INDEX}"
                         # --use-feature=in-tree-build

cmake/modules/DuneSphinxCMakeDoc.cmake

@@ -157,7 +157,7 @@ function(dune_cmake_sphinx_doc)
   foreach(module ${SPHINX_DOC_MODULE_LIST})
     get_filename_component(modname ${module} NAME)
     add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/modules/${modname}
-                       COMMAND ${Python3_EXECUTABLE} ${DUNE_SPHINX_EXT_PATH}/extract_cmake_data.py
+                       COMMAND Python3::Interpreter ${DUNE_SPHINX_EXT_PATH}/extract_cmake_data.py
                          --module=${module}
                          --builddir=${CMAKE_CURRENT_BINARY_DIR}
                        DEPENDS ${module}