MPI Autocompletion in Visual Studio Code - visual-studio-code

Question

I'm trying to use Visual Studio Code to develop Fortran MPI programs. However, while I can successfully build and run them just fine, it would be very helpful for me if I can use intellisense/autocompletion features for MPI (as well as other external modules). I have /usr/lib/openmpi/ (which contains mpi_f08.mod) as part of fortran.includePaths in my settings.json. However, when I use mpi_f08, I get the problem message from VS Code Module "mpi_f08" not found in project. Here is a minimal CMake build example:
! hello.f90
program hello
use mpi_f08
implicit none
integer :: ierror, nproc, my_rank
call MPI_Init()
call MPI_Comm_size(MPI_COMM_WORLD, nproc, ierror)
call MPI_Comm_rank(MPI_COMM_WORLD, my_rank, ierror)
print*, "hello from rank ", my_rank
call MPI_Finalize()
end program hello
# CMakeLists.txt
cmake_minimum_required(VERSION 3.12)
project(hello_mpi)
enable_language(Fortran)
find_package(MPI REQUIRED)
add_executable(hello_mpi hello.f90)
include_directories(${MPI_Fortran_INCLUDE_PATH})
target_link_libraries(hello_mpi PUBLIC ${MPI_Fortran_LIBRARIES})
I would like to be able to (i) get rid of the warning/message and more importantly (ii) enable suggestions from MPI when I press CTRL+space as it would if I was calling from an internal module.

Answer 1

I'll post a partial answer since it's better than nothing, hopefully this helps someone else and/or enables someone else to answer my question fully.
It seems the issue relates to the Fortran language server, which can be configured by adding a .fortls JSON file, as explained on its Github README: https://github.com/hansec/fortran-language-server
I added the following, which allowed it to find not only local modules but also MPI (and the external module json-fortran):
{
"source_dirs": ["src", "."],
"ext_source_dirs": [
"/path/to/json-fortran/src",
"/path/to/openmpi-4.1.2/ompi/mpi/fortran/use-mpi-f08",
]
}
This doesn't capture all functions in json-fortran, which I think is because of its .inc files, as it doesn't give me function pointers like json_file::get at autocomplete.
As for MPI, this kind of works, as it gives me all the functions I can think of needing, but with _f08 appended to the end of it. I don't know the inner workings of OpenMPI but I guess e.g. MPI_Init wraps MPI_Init_f08 for reasons of backward compatibility. For now I can simply autocomplete to the _f08 version and remove that bit manually. (I also tried adding openmpi-4.1.2/ompi/mpi/fortran/use-mpi-tkr and openmpi-4.1.2/ompi/mpi/fortran/mpif.h but no luck).
Would be nice to get this detail sorted though. It is also mildly annoying that I must manually include the source dirs now (removing it makes it not find local modules).