RFC: Provide install script

[frabert]

Multiplier is using weggli-native in a CMake project via Corrosion, which works well enough as for now.
The issue is that if Multiplier is used as a library and weggli-native is exposed as a transitive dependency, everything breaks.

I created a script that can be used to install the library and the generated header to a chosen directory, together with a CMake config module that allows users to find the library by doing find_package(weggli_native).

I'm open to hearing different approaches

[CLAassistant]

All committers have signed the CLA.

[woodruffw]

Hmm. I'm generally not a huge fan of opaque install scripts -- perhaps we could just add the CMake build and config module directly, and have it invoke the Rust build + provide the right installation targets?

[frabert]

That sounds interesting, but I'm not sure how exactly it would work. Can you give me more details about what you have in mind?

[woodruffw]

Can you give me more details about what you have in mind?

I had something like uthenticode's CMake build in mind: https://github.com/trailofbits/uthenticode

In particular, we use CMake's install and export directives to copy everything, and to auto-generate a CMake user config:

install(
  TARGETS "${PROJECT_NAME}"
  EXPORT uthenticode-targets
  RUNTIME DESTINATION "bin"
  LIBRARY DESTINATION "lib"
  ARCHIVE DESTINATION "lib"
  PUBLIC_HEADER DESTINATION "include"
)
export(
  TARGETS "${PROJECT_NAME}"
  NAMESPACE uthenticode::
  FILE "${CMAKE_CURRENT_BINARY_DIR}/uthenticode-targets.cmake"
)
install(
  EXPORT uthenticode-targets
  DESTINATION "lib/cmake/uthenticode"
  NAMESPACE uthenticode::
  EXPORT_LINK_INTERFACE_LIBRARIES
)
install(FILES uthenticode-config.cmake DESTINATION "lib/cmake/uthenticode")

[frabert]

Ok so here is how far I was able to get:

cmake_minimum_required(VERSION 3.19)

project(weggli_native)

if(NOT ((CMAKE_BUILD_TYPE STREQUAL "Release") OR (CMAKE_BUILD_TYPE STREQUAL "Debug")))
    message(FATAL_ERROR "Only Debug and Release builds are supported")
endif()

find_program(CARGO "cargo" REQUIRED)
find_program(CBINDGEN "cbindgen" REQUIRED)

if(CMAKE_BUILD_TYPE STREQUAL "Release")
    set(CARGO_PROFILE "release")
else()
    set(CARGO_PROFILE "dev")
endif()

string(TOLOWER "${CMAKE_BUILD_TYPE}" TARGET_DIR)

add_custom_target(cargo_build
    COMMAND "${CARGO}" build --profile "${CARGO_PROFILE}"
    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}")

add_custom_command(
    OUTPUT "${CMAKE_BINARY_DIR}/weggli.h"
    COMMAND "${CBINDGEN}" ARGS -o "${CMAKE_BINARY_DIR}/weggli.h"
    MAIN_DEPENDENCY cargo_build)

add_library(weggli::weggli_native-static STATIC IMPORTED)
add_dependencies(weggli::weggli_native-static cargo_build)
set_target_properties(weggli::weggli_native-static
    PROPERTIES
        PUBLIC_HEADER "${CMAKE_BINARY_DIR}/weggli.h"
        IMPORTED_LOCATION "${CMAKE_SOURCE_DIR}/target/${TARGET_DIR}/libweggli_native.a")

add_library(weggli::weggli_native-shared STATIC IMPORTED)
add_dependencies(weggli::weggli_native-shared cargo_build)
set_target_properties(weggli::weggli_native-shared
    PROPERTIES
        PUBLIC_HEADER "${CMAKE_BINARY_DIR}/weggli.h"
        IMPORTED_LOCATION "${CMAKE_SOURCE_DIR}/target/${TARGET_DIR}/libweggli_native.dylib")

install(
    TARGETS weggli::weggli_native-static weggli::weggli_native-shared
    EXPORT weggli_native-targets
    RUNTIME DESTINATION "bin"
    LIBRARY DESTINATION "lib"
    ARCHIVE DESTINATION "lib"
    PUBLIC_HEADER DESTINATION "include")

problem is, imported targets cannot be installed...

EDIT: also, it seems like it would involve an annoying amount of work to be cross platform

[frabert]

This last CMake file is the best I could come up with. I think it's good, but it's not perfect, as the weggli_native-config.cmake file is hardcoded with the CMAKE_PREFIX_PATH inserted during configuration, so it doesn't work properly if another path is passed to cmake --install

[woodruffw]

Looks pretty good to me. If you're okay with the minor caveat around CMAKE_PREFIX_PATH we can merge for now, and try to come up with a better workaround later.

(We should also look into testing this build in the CI to ensure that we don't accidentally break it, but we that can be another follow-up task for another time.)

[frabert]

Yes I think it's sufficient for my uses right now. Things for the future:

• Windows probably doesn't work like this, as it needs both a .lib and a .dll file for dynamic libraries
• CMAKE_PREFIX_PATH is hardcoded
• Needs testing

[woodruffw]

Sounds good. Mind opening a tracking issue for those?