Merge topic 'FindMPI-improve-error'

e221039e11 FindMPI: Improve error when a component's language is not enabled

Acked-by: Kitware Robot <[email protected]>
Acked-by: Ben Boeckel <[email protected]>
Merge-request: !4071

Modules/FindMPI.cmake

@@ -1391,6 +1391,7 @@ foreach(LANG IN ITEMS C CXX Fortran)
     endif()
   else()
     set(_MPI_FIND_${LANG} FALSE)
+    string(APPEND _MPI_FAIL_REASON "MPI component '${LANG}' was requested, but language ${LANG} is not enabled.  ")
   endif()
   if(_MPI_FIND_${LANG})
     if( ${LANG} STREQUAL CXX AND NOT MPICXX IN_LIST MPI_FIND_COMPONENTS )
@@ -1688,6 +1689,7 @@ endif()
 find_package_handle_standard_args(MPI
     REQUIRED_VARS ${_MPI_REQ_VARS}
     VERSION_VAR ${_MPI_MIN_VERSION}
+    REASON_FAILURE_MESSAGE "${_MPI_FAIL_REASON}"
     HANDLE_COMPONENTS)
 
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