[magnum/magnum-plugins] fix magnum-plugins building all magnum dependencies

[fran6co]

Describe the pull request

Fixes error:

  By not providing "FindAssimp.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "Assimp", but
  CMake did not find one.
  Could not find a package configuration file provided by "Assimp" with any
  of the following names:
    AssimpConfig.cmake
    assimp-config.cmake
  Add the installation prefix of "Assimp" to CMAKE_PREFIX_PATH or set
  "Assimp_DIR" to a directory containing one of the above files.  If "Assimp"
  provides a separate development package or SDK, be sure it has been
  installed.

The assimp library in vcpkg is all lower case and Magnum expects it camel case.

Also installing magnum-plugins triggers the installation of all the features in magnum.

[PhoebeHui]

@fran6co, thanks for the PR! could you update the baseline version?

Error: While reading versions for port magnum-plugins from file: C:\a\1\s\versions\m-\magnum-plugins.json
       Version `2020.06#4` was not found in versions file.
       Run:

           vcpkg x-add-version magnum-plugins

       to add the new port version.
To attempt to resolve all errors at once, run:

    vcpkg x-add-version --all

[fran6co]

@PhoebeHui done

[PhoebeHui]

Thanks for your updates!

[ras0219-msft]

Thanks for the PR! This LGTM. +@Squareys +@mosra to possibly review this, otherwise I'll merge tomorrow.

[mosra]

The assimp library in vcpkg is all lower case and Magnum expects it camel case.

We don't, we deliberately use Assimp instead of assimp and provide our own FindAssimp.cmake in order to fix various issues with Assimp's own CMake files, incomplete packaging in Homebrew and elsewhere... This change will only cause additional headaches on our side due to potential patch conflicts. I think the root cause is something else.

@fran6co may I ask where did you get this error? Was it during the package build or when using the magnum-plugins vcpkg package in your project?

---

(@ras0219-msft thanks a lot for the ping, is there some automated way to have @Squareys and me pinged on magnum package updates? It could save us a lot of time. Maybe through some CODEOWNERS file?)

[fran6co]

@mosra it happens when I'm using magnum-plugins. When I add the project with this:

find_package(MagnumPlugins CONFIG REQUIRED AssimpImporter)
target_link_libraries(app PRIVATE MagnumPlugins::AssimpImporter)

I get this error:

  Target "app" links to target "Assimp::Assimp" but the target was not
  found.  Perhaps a find_package() call is missing for an IMPORTED target, or
  an ALIAS target is missing?

If I add the alias of assimp::assimp to Assimp::Assimp I get the error I mentioned before:

 By not providing "FindAssimp.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "Assimp", but
  CMake did not find one.
  Could not find a package configuration file provided by "Assimp" with any
  of the following names:
    AssimpConfig.cmake
    assimp-config.cmake
  Add the installation prefix of "Assimp" to CMAKE_PREFIX_PATH or set
  "Assimp_DIR" to a directory containing one of the above files.  If "Assimp"
  provides a separate development package or SDK, be sure it has been
  installed.

[fran6co]

Maybe the proper solution would be adding to the installation MagnumPlugins's FindAssimp.cmake as it's not being copied as part of the package

[mosra]

Ah, I remember an older issue opened by you as well, coincidentally: mosra/magnum#436 For the reasons stated there, the solution (until I get this finally fixed) is to copy FindAssimp.cmake to your project module directory :)

The same behavior is with most other 3rd party dependencies in Magnum, so I don't think doing a patch inside vcpkg makes sense.

[fran6co]

Ah, forgot about that... Well, I guess I can do the same, I'll remove the assimp change but keep the [core] change to avoid installing all magnum dependencies

[mosra]

keep the [core] change to avoid installing all magnum dependencies

Missed this one completely. Good idea 👍

I'll ping you once mosra/magnum#436 gets fixed properly in Magnum itself :)

[ras0219-msft]

I think CODEOWNERS won't work due to write permissions, but we do have a maintainers field: https://github.com/microsoft/vcpkg/blob/master/docs/maintainers/manifest-files.md#maintainers

[ras0219-msft]

LGTM, thanks everyone!