Using dependencies to enhance header search path with compiler.has_header

[mitchgrout]

Let's say I'm consuming some dependency, foo. This dependency might have a header in it named foo/config.h, and I would like to detect this within meson.

My immediate thought is to write the following code:

c   = meson.get_compiler('c')
dep = dependency('foo')

# For the example, just asserting it must exist
c.has_header('foo/config.h', dependencies: dep, required: true)

However, this fails even if a #include <foo/config.h> would otherwise pass in an equivalent executable. My guess it that the dependencies part of compiler.check_header does not contribute include headers (as evidenced by the meson-logs.txt command), which seems odd?

My question is whether this is intentional, and if so what benefit it serves?

My intended use for this is primarily for sanity checking, since I want to detect if a <libname>-config dependency exists, and if so assert that the corresponding <libname>/config.h header exists to avoid getting the error deferred to compilation. It's effectively like a replacement for __has_include.