`doc` attribute doesn't behave like rustc does

[TheKK]

Inputs

#[no_mangle]
#[doc = "a \n b"]
pub extern "C" fn example_a() {}

and

#[no_mangle]
#[doc = "a \n\n b"]
pub extern "C" fn example_b() {}

Rendered rustdoc

rustdoc/the doc attribute

Actual generated header

///a
 b
void example_a();

///a

 b
void example_b();

Expected generated header

///a b
void example_a();

///a
///
///b
void example_b();

This happens when I'm trying to generate multi-line comments with macro. Looks like (code) we simply use value in single doc attribute directly without any modification (like rustdoc does).

BTW, I'm happy to help this out :)

[emilio]

Yeah, it'd be great to get this fixed :)

[TheKK]

After some researching I got some questions. Should I implement this translation by myself or using other crate?

One thing that bother me is that the spec of markdown line break is a bit vague. The algorithm isn't obvious to me. It might works for most cases but I'm afraid there would be missing one :(

Using crate might be overkill, on the other hand.

Any suggestions?

[emilio]

Can you clarify? I (maybe naively) was thinking that just unescaping \n would do.

Why isn't this just a matter of splitting/un-escaping \n characters in the #[doc] attribute? I don't think we need to generate perfect markdown, just not generate broken code.

[TheKK]

Can you clarify? I (maybe naively) was thinking that just unescaping \n would do.

I found that line end with two space is the other case markdown would cause line break.

Maybe my concern here is that should we expect the Rust source file used for generating good C/C++ header, also generating good Rust document using rustdoc? I think this might depends on use case.

(good means correct line break)