Expose `mdbook` as a Library

[UebelAndre]

Problem

Howdy, I would like to include the mdbook binary in some tooling and due to rust-lang/cargo#9096 not yet being stabilized, getting access to the mdbook binary is pretty tricky after the 0.5.0 release and requires additional infrastructure or extra complex scripting to make sure it's available.

Proposed Solution

Would it be acceptable by the maintainers to make src/main.rs into a library where the only public function is main?

Notes

This used to work prior to the 0.5.0 release but now the existing tooling would require a nightly toolchain.

[ehuss]

Can you say more about what your usecase is? Almost everything should be available via mdbook-driver. That is the library that is intended for high-level usage.

[UebelAndre]

I maintain https://bazelbuild.github.io/rules_rust/rust_mdbook.html which are Bazel rules that wrap mdbook. Currently mdbook is built from source by default using additional infra in the same repository. Because there is no library in the current mdbook crate, I get hit by rust-lang/cargo#9096 and now need to re-implement the entry-point on my own. I had a similar issue with wasm-bindgen wasm-bindgen/wasm-bindgen#4653

[UebelAndre]

I'd also be happy to do the work to make this happen. I'd just need a maintainer to give the go-ahead. I understand, however, it's an odd scenario.