Create imported targets in DARTFind*.cmake instead of Find*.cmake

[mxgrey]

This attempts to fix the issue reported in the thread of #1209

[jslee02]

Looks good to me! Let's add an item for this change in the changelog under DART 6.7.1.

[mxgrey]

@jslee02 I'm looking over the cmake scripts for finding packages, and I'm not clear on one thing: What happens when the dependency of a component is missing? For example, let's say I install libdart with libdart-utils which depends on libtinyxml2, but later I forcibly delete libtinxyml2. Then I call find_package(DART REQUIRED COMPONENT utils). Ideally cmake should recognize that tinxyml2 is no longer available and then make the configuration fail.

I think that'll work fine for core dependencies, because we use find_package(... REQUIRED) on those, but the components don't use REQUIRED in their DARTFind*.cmake files, so I don't think this situation will be caught.

Please let me know if I'm overlooking something. In the meantime I'll see if I can find a minimally invasive way to make the config-file work as desired.

[jslee02]

I also think the current script wouldn't catch the case, which I believe most of the build scripts wouldn't do either (because the system has been forcibly changed from when it was built). But it sounds good to have a logic to catch the case.

[jslee02]

One possible solution would be:

• Change all the current DARTFind<package>.cmake files into macros and put it in one file (e.g., DARTFindPackages.cmake)
• Make the macros to have an option whether finding the package required or not
• Find packages with or without required option when DART is built depending on whether the package is options
• Find packages with required option in DARTConfig.cmake

[mxgrey]

CMake config-files are encouraged to use find_dependency() which will pass along the REQUIRED and QUIET properties from the config-file or find-module that uses it. When a required dependency isn't found, the configuration will fail. Ideally that's the kind of behavior we should aim for.

Unfortunately find_dependency(~) only helps in very narrow circumstances, and I don't think it'll help us out much here. I have some ideas about a solution, though. I'll open a separate PR for that, though, since it's mostly orthogonal to this issue.

[mxgrey]

I'm thinking about using the dart_*Component.cmake files to handle the REQUIRED behavior. It looks like those files are automatically generated, so it should be pretty straightforward to put the behavior into them. I just need to find how those files get created.

[jslee02]

Unfortunately find_dependency(~) only helps in very narrow circumstances, and I don't think it'll help us out much here.

Yeah, AFAIK, find_dependency() does not support COMPONENTS or MODULE until 3.8.0.

I'll open a separate PR for that, though, since it's mostly orthogonal to this issue.

👍

[jslee02]

I just need to find how those files get created.

Those files are generated by these lines in Components.cmake.

[jslee02]

LGTM!