Arch Linux

__Sorry for the formatting issue, fixed code excerpts from the VTK CMake config___

```vtk-config.cmake
unset("${CMAKE_FIND_PACKAGE_NAME}_FOUND")
set("${CMAKE_FIND_PACKAGE_NAME}_HAS_VTKm" "ON")
if (${CMAKE_FIND_PACKAGE_NAME}_HAS_VTKm)
find_package(VTKm PATHS "${CMAKE_CURRENT_LIST_DIR}/vtkm" NO_DEFAULT_PATH)
if (NOT VTKm_FOUND)
set("${CMAKE_FIND_PACKAGE_NAME}_FOUND" 0)
endif ()
endif ()
```

```VTKmConfig.cmake
# VTKm_ENABLE_TBB Will be enabled if VTK-m was built with TBB support

set(VTKm_ENABLE_TBB "ON")

if (VTKm_ENABLE_TBB)
find_dependency(TBB)
if (NOT TBB_FOUND)
set(VTKm_FOUND 0)
list(APPEND VTKm_NOT_FOUND_REASON "TBB not found: ${TBB_NOT_FOUND_MESSAGE}")
endif()
endif()
```

The same is applicable to `openmpi`
```vtkm/VTKmConfig.cmake
set(VTKm_ENABLE_OPENMP "ON")
set(VTKm_ENABLE_MPI "ON")
```

```vtkm/cmake/VTKmWrappers.cmake
if(VTKm_ENABLE_MPI AND NOT TARGET MPI::MPI_CXX)
find_package(MPI REQUIRED MODULE)
endif()
```

tbb was added but in our tests it was the only one really required. Can you confirm?

Nope: Check out this bare PKGBUILD with `vtk,tbb` in depends array building a boilerplate `CMakeLists.txt` witch just calls `find_package(VTK)`

It fails complaining about missing `openmpi`


`PKGBUILD`
```
pkgname=test
pkgver=1.0
pkgrel=1
arch=(x86_64)
depends=(vtk tbb)
makedepends=(cmake)
source=(CMakeLists.txt)
sha256sums=('SKIP')
package() {
cmake -S "$srcdir" -B build
}
```

`CMakeList.txt`
```
cmake_minimum_required(VERSION 3.2)
project(test)
find_package(VTK REQUIRED COMPONENTS vtkCommonCore)
```

`extra-x86_64-build.log`
```
...

-- Could NOT find MPI_CXX (missing: MPI_CXX_LIB_NAMES MPI_CXX_HEADER_DIR MPI_CXX_WORKS)
CMake Error at /usr/share/cmake-3.22/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
Could NOT find MPI (missing: MPI_C_FOUND MPI_CXX_FOUND)
Call Stack (most recent call first):
/usr/share/cmake-3.22/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
/usr/share/cmake-3.22/Modules/FindMPI.cmake:1830 (find_package_handle_standard_args)
/usr/lib/cmake/vtk/vtkm/cmake/VTKmWrappers.cmake:18 (find_package)
/usr/lib64/cmake/vtk/vtkm/VTKmConfig.cmake:173 (include)
/usr/lib64/cmake/vtk/vtk-config.cmake:129 (find_package)
CMakeLists.txt:3 (find_package)
```

@bartoszek the changes were made in vtk 9.1.0-4 currently in testing. Can you please retest against the testing repositories?

Same error with `testing-x86_64-build` should I also test against `staging` repository?

If you add openmpi to makedepends the test PKGBUILD then works? That leaves the question if openmpi should be a dependency of vtk rather than an optional dependency.

As shown in https://bugs.archlinux.org/task/72727#comment203663 if vtk was build with openmpi it becomes hard dependency of vtkm. And yes, including openmpi in depends array fixes the `find_package(VTK)` in my example.

opencv 4.5.4-7 uses vtk but not vtkm so it has openmpi in makedepends, opencascade 7.5.3-4 is similar it has a made depend on adios2 which depends on openmpi.

vtk-m is a third party deps of vtk and as far as I can tell there's no way to build vtk without vtk-m.

`find_package(VTKm)` is guarded by `VTK_HAS_VTKm` variable which is set to `ON` if `vtk::vtkm` target exist during build.

https://gitlab.kitware.com/vtk/vtk/-/blob/master/CMake/vtk-config.cmake.in#L127

Moreover, `openmp` becomes hard dependency when you build a project with `clang` and links to `vtk:9.1`

Sorry for the huge delay here. So what your saying is that when you try to build something with VTK, you need both openmpi and openmp in addition to TBB for things to work. When I look at things like https://github.com/archlinux/svntogit-community/commit/86c6cc30126b0b71f71ff5dfcbf24f6bd4beb900 also, I’m starting to wonder if VTK is doing things right there. It seems to be bringing way too much dependencies everywhere, so I’m not sure what to do. They are also issues in https://bugs.archlinux.org/task/61655 about current handling of dependencies.