From 834569258036688ca939bd6d29aafe500636d5ad Mon Sep 17 00:00:00 2001
From: Cristian Le <cristian.le@mpsd.mpg.de>
Date: Tue, 11 Jun 2024 11:07:22 +0200
Subject: [PATCH] Fix MPI support

Signed-off-by: Cristian Le <cristian.le@mpsd.mpg.de>
---
 CMakeLists.txt                 |  5 ++++-
 cmake/Wannier90Config.cmake.in | 16 ++++++++++++++++
 src/CMakeLists.txt             |  5 ++++-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5c2abc7e3..a9f380f70 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -76,7 +76,10 @@ set(Wannier90_MPI ${WANNIER90_WITH_MPI})
 find_package(BLAS REQUIRED)
 find_package(LAPACK REQUIRED)
 if (WANNIER90_MPI)
-	find_package(MPI REQUIRED)
+	find_package(MPI REQUIRED COMPONENTS Fortran)
+	if (NOT MPI_Fortran_HAVE_F08_MODULE)
+		message(SEND_ERROR "mpi_f08 module is required for building Wannier90 with MPI")
+	endif ()
 endif ()
 
 #[=============================================================================[
diff --git a/cmake/Wannier90Config.cmake.in b/cmake/Wannier90Config.cmake.in
index af6ec851c..062055458 100644
--- a/cmake/Wannier90Config.cmake.in
+++ b/cmake/Wannier90Config.cmake.in
@@ -4,5 +4,21 @@
 ## Define basic variables
 set(Wannier90_MPI @WANNIER90_MPI@)
 
+## Include dependencies
+include(CMakeFindDependencyMacro)
+if (Wannier90_MPI)
+	# Note: In the future the MPI support can be converted to an (optional) package component.
+	# This would however require a breaking change in the library definition
+	find_dependency(MPI COMPONENTS Fortran)
+	if (NOT MPI_Fortran_FOUND OR NOT MPI_Fortran_HAVE_F08_MODULE)
+		message(WARNING
+				"Wannier90 was built and packaged with MPI, but the system does not have compatible MPI support.\n"
+				"This is an issue with the packager of Wannier90."
+		)
+		set(${CMAKE_FIND_PACKAGE_NAME}_FOUND FALSE)
+		return()
+	endif ()
+endif ()
+
 ## Parse find_package request
 include(${CMAKE_CURRENT_LIST_DIR}/Wannier90Targets.cmake)
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d2a2cba42..38c0aa13b 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -44,7 +44,10 @@ target_sources(Wannier90_lib
 		${CMAKE_Fortran_MODULE_DIRECTORY}/w90_library.mod
 )
 if (WANNIER90_MPI)
-	target_link_libraries(Wannier90_lib PRIVATE MPI::MPI_Fortran)
+	target_link_libraries(Wannier90_lib PUBLIC MPI::MPI_Fortran)
+	target_compile_definitions(Wannier90_lib PRIVATE
+			MPI08 MPI
+	)
 endif ()
 
 add_subdirectory(postw90)