Handle optional dependencies by directly passing HAVE_xxx flags

cmake/modules/AddMETISFlags.cmake

@@ -17,10 +17,18 @@ include_guard(GLOBAL)
 # register HAVE_METIS for config.h
 set(HAVE_METIS ${METIS_FOUND})
 
+set(METIS_COMPILE_DEFINITIONS)
+if(HAVE_METIS)
+  list(APPEND METIS_COMPILE_DEFINITIONS "HAVE_METIS=1")
+endif()
+if(HAVE_SCOTCH_METIS)
+  list(APPEND METIS_COMPILE_DEFINITIONS "HAVE_SCOTCH_METIS=1")
+endif()
+
 # register METIS library as dune package
 if(METIS_FOUND)
   dune_register_package_flags(LIBRARIES METIS::METIS
-    COMPILE_DEFINITIONS "ENABLE_METIS=1")
+    COMPILE_DEFINITIONS ${METIS_COMPILE_DEFINITIONS})
 endif()
 
 # Add function to link targets against METIS library
@@ -28,7 +36,7 @@ function(add_dune_metis_flags _targets)
   if(METIS_FOUND)
     foreach(_target ${_targets})
       target_link_libraries(${_target} PUBLIC METIS::METIS)
-      target_compile_definitions(${_target} PUBLIC ENABLE_METIS=1)
+      target_compile_definitions(${_target} PUBLIC ${METIS_COMPILE_DEFINITIONS})
     endforeach(_target)
   endif()
 endfunction(add_dune_metis_flags _targets)

cmake/modules/AddPTScotchFlags.cmake

@@ -20,24 +20,24 @@ set(HAVE_PTSCOTCH ${PTScotch_FOUND})
 # register all PTScotch related flags
 if(PTScotch_SCOTCH_FOUND)
   dune_register_package_flags(LIBRARIES PTScotch::Scotch
-    COMPILE_DEFINITIONS "ENABLE_SCOTCH=1")
+    COMPILE_DEFINITIONS "HAVE_SCOTCH=1")
 endif()
 if(PTScotch_PTSCOTCH_FOUND)
   dune_register_package_flags(LIBRARIES PTScotch::PTScotch
-    COMPILE_DEFINITIONS "ENABLE_PTSCOTCH=1")
+    COMPILE_DEFINITIONS "HAVE_PTSCOTCH=1")
 endif()
 
 function(add_dune_ptscotch_flags _targets)
   if(PTScotch_SCOTCH_FOUND)
     foreach(_target ${_targets})
       target_link_libraries(${_target} PUBLIC PTScotch::Scotch)
-      target_compile_definitions(${_target} PUBLIC ENABLE_SCOTCH=1)
+      target_compile_definitions(${_target} PUBLIC HAVE_SCOTCH=1)
     endforeach(_target ${_targets})
   endif()
   if(PTScotch_PTSCOTCH_FOUND)
     foreach(_target ${_targets})
       target_link_libraries(${_target} PUBLIC PTScotch::PTScotch)
-      target_compile_definitions(${_target} PUBLIC ENABLE_PTSCOTCH=1)
+      target_compile_definitions(${_target} PUBLIC HAVE_PTSCOTCH=1)
     endforeach(_target ${_targets})
   endif()
 endfunction(add_dune_ptscotch_flags)

cmake/modules/AddParMETISFlags.cmake

@@ -17,10 +17,18 @@ include_guard(GLOBAL)
 # set HAVE_PARMETIS for config.h
 set(HAVE_PARMETIS ${ParMETIS_FOUND})
 
+set(PARMETIS_COMPILE_DEFINITIONS)
+if(HAVE_PARMETIS)
+  list(APPEND PARMETIS_COMPILE_DEFINITIONS "HAVE_PARMETIS=1")
+endif()
+if(HAVE_SCOTCH_METIS)
+  list(APPEND PARMETIS_COMPILE_DEFINITIONS "HAVE_PTSCOTCH_PARMETIS=1")
+endif()
+
 # register all ParMETIS related flags
 if(ParMETIS_FOUND)
   dune_register_package_flags(LIBRARIES ParMETIS::ParMETIS
-    COMPILE_DEFINITIONS "ENABLE_PARMETIS=1")
+    COMPILE_DEFINITIONS ${PARMETIS_COMPILE_DEFINITIONS})
 endif()
 
 # add function to link against the ParMETIS library
@@ -28,7 +36,7 @@ function(add_dune_parmetis_flags _targets)
   if(ParMETIS_FOUND)
     foreach(_target ${_targets})
       target_link_libraries(${_target} PUBLIC ParMETIS::ParMETIS)
-      target_compile_definitions(${_target} PUBLIC ENABLE_PARMETIS=1)
+      target_compile_definitions(${_target} PUBLIC ${PARMETIS_COMPILE_DEFINITIONS})
     endforeach(_target)
   endif()
 endfunction(add_dune_parmetis_flags)

config.h.cmake

@@ -99,21 +99,6 @@
 /// \deprecated Use HAVE_SUITESPARSE_UMFPACK instead
 #define HAVE_UMFPACK HAVE_SUITESPARSE_UMFPACK
 
-/* Define to 1 if METIS is available */
-#cmakedefine HAVE_METIS ENABLE_METIS
-
-/* Define to 1 if the Scotch replacement for METIS is used. */
-#cmakedefine HAVE_SCOTCH_METIS 1
-
-/* Define to 1 if you have the ParMETIS library. */
-#cmakedefine HAVE_PARMETIS ENABLE_PARMETIS
-
-/* Define to 1 if the PTScotch replacement for ParMETIS is used. */
-#cmakedefine HAVE_PTSCOTCH_PARMETIS 1
-
-/* Define to 1 if PT-Scotch is available */
-#cmakedefine HAVE_PTSCOTCH ENABLE_PTSCOTCH
-
 /* Used to call lapack functions */
 #cmakedefine LAPACK_NEEDS_UNDERLINE