[Feature Request] Add a config option to add dependencies for a specific struct / type

[bavalpey]

I have this issue where I am adding non abi-breaking methods to some of the structs emitted by cbindgen. However, some of them require the full definition of other structures to be emitted before.

For example, I have something equivalent to the following in my cbindgen.toml

[export.body]
"Bar" = """
public:
  bar_method(Foo::Tag tag);
"""

(I am defining the body of bar_method using the trailing configuration option).

In this case, a simple forward declaration for Foo will not work, as I specifically want to use the generated Tag field. FWIW, the rust code for Foo would look something like this:

pub enum Foo {
   MyFoo1(u8),
   MyFoo2(u8),
}

I saw issue #43 which is similar in a way. I think that having a field in the [export] table (similar to [export.body]) that allows manually specifying a dependency for an item would be beneficial. This feature would work as a workaround for that issue, in that we could use this configuration option to get around deficiencies in the dependency logic.

Right now, what I am doing is actually adding Foo to [export.exclude], and then putting what cbindgen would generate for it in the after_includes configuration field. This is fairly brittle, however, as I have to remember to change it should the definition of Foo ever change.