[C++] CMake Windows Install - Wrong Config File Locations

[WillAyd]

Describe the bug, including details regarding any error messages, version, and platform.

The way CMake installs Arrow on Windows does not follow CMake's requirements for subsequently finding config files. The consequence of this is that the default find_package() calls from third parties will fail to find arrow libraries correctly.

The CMake Docs list the patterns by which find_package will discover files like ArrowConfig.cmake and ArrowComputeConfig.cmake. Some patterns are Windows-only, some are Unix-only. The cross-platform search paths are:

<prefix>/<name>*/(lib/<arch>\|lib*\|share)/cmake/<name>*/ 
<prefix>/<name>*/(lib/<arch>\|lib*\|share)/<name>*/ 
<prefix>/<name>*/(lib/<arch>\|lib*\|share)/<name>*/(cmake\|CMake)/

When the CMAKE_INSTALL_PREFIX is not overriden, Arrow installs configs for the main library and compute to:

C:/Program Files/arrow/lib/cmake/Arrow/ArrowConfig.cmake
C:/Program Files/arrow/lib/cmake/ArrowCompute/ArrowComputeConfig.cmake

Ignoring case, this allows find_package(Arrow) to work because that matches the <prefix>/<name>*/(lib/<arch>\|lib*\|share)/cmake/<name>*/ convention; however, find_package(ArrowCompute) fails.

If you specify a INSTALL_PREFIX like C:\arrow-dist, you end up with:

C:/arrow-dist/lib/cmake/Arrow/ArrowConfig.cmake
C:/arrow-dist/lib/cmake/ArrowCompute/ArrowComputeConfig.cmake

In this case, neither config file can be found by find_package, assumedly because CMake expects the name to appear after the <prefix>

This was discovered in my fork of Arrow with the help of @raulcd

Component(s)

C++

[kou]

It may be better that we use find_package(Arrow COMPONENTS Compute) instead of find_package(ArrowCompute).
(But we should keep find_package(ArrowCompute) for backward compatibility.)

[kou]

Workaround for C:/Program Files/arrow: Use -DArrowCompute_ROOT=C:/Program Files/arrow/lib/cmake/ArrowCompute.

Workaround for C:/arrow-dist: Use -DArrow_ROOT=C:/arrow-dist/lib/cmake/Arrow -DArrowCompute_ROOT=C:/arrow-dist/lib/cmake/ArrowCompute.

[WillAyd]

It may be better that we use find_package(Arrow COMPONENTS Compute) instead of find_package(ArrowCompute). (But we should keep find_package(ArrowCompute) for backward compatibility.)

Ah OK interesting - is that the canonical way to search for all of the non-Arrow libraries?

This was originally discovered via the meson wrapper to CMake. It looks like that supports the component argument, so we could try to switch over to that

https://mesonbuild.com/Dependencies.html#cmake

[kou]

is that the canonical way to search for all of the non-Arrow libraries?

It means that we should support find_package(Arrow COMPONENTS Compute Parquet Gandiva ...) not only ArrowCompute, right?
If so, yes. If we support COMPONENTS, all our CMake packages should work with COMPONENTS.