Support wrap testing with other wrap dependencies

[jpakkane]

Carrying on the discussion from imgui-sfml:

The imgui dependency has been tested to work with the imgui that is available in wrapdb. So if people do meson wrap install imgui-sfml and meson wrap install imgui then it should work.

Once we start adding provides entries to wrap files, testing these could be made to work out of the box since for any dependency we will be able to easily tell if it can be obtained via wrapdb. This requires some code, of course, but it should not be fairly straightforward.

[legeana]

@jpakkane So let's say imgui-sfml depends on imgui. What is the correct way to get the list of dependencies from the wrap itself if I build it as a root-level project? Currently this is the way I test wraps on submission.

[jpakkane]

Err. Turns out that I was thinking about this the wrong way around. However, this should work:

• create a new empty project
• add all wrap files in the wrapdb in the subprojects dir
• create a top level Meson file that basically does subproject('the-thing-to-test')

If all wrap files have provides entries, this should work.

[jpakkane]

To clarify: this should already work if all wrap projects set up subproject fallbacks properly. Once we have provides it should work with just dependency('foobar').

[dreamer-coding]

What about a requires section? Maybe that would be helpful for doing additional wrap downloads ahead of time before running the download process on whatever dependency or dependencies the user is using.