Add (optional) `doc_auto_cfg` attribute to generated library

[robamu]

In my crates, I currently use the following code snippet at the top of lib.rs:

#![cfg_attr(docsrs, feature(doc_auto_cfg))]

For documentation built by docs.rs, this explicitly displays required features for modules/functions etc. without requiring additional attributes. What do you think about adding this to the generated library?

In all my libraries using this, I use the following snippets in Cargo.toml to use this for the docs-rs build:

[package.metadata.docs.rs]
rustdoc-args = ["--generate-link-to-definition"]

[robamu]

Actually, I have issue building this locally without warnings with current nightly.

Adding the following snippet to Cargo.toml:

[lints.rust]
unexpected_cfgs = { level = "warn", check-cfg = ['cfg(docs_rs)'] }

fixes the warning ,but the documentation still is not built properly.. In any case https://docs.rs/va108xx/0.3.0/va108xx/ shows the end result , with the documentation displaying where the rt feature is required.

[robamu]

After some more research:

It is sufficient to use

#![cfg_attr(docsrs, feature(doc_auto_cfg))]

in the lib.rs. The docsrs configuration will be set by docs-rs automatically. In the Cargo.toml

[package.metadata.docs.rs]
rustdoc-args = ["--generate-link-to-definition"]

is sufficient now.

The old way I used to build this locally does not work anymore. I tested this locally using

RUSTDOCFLAGS="--cfg docsrs --generate-link-to-definition -Z unstable-options" cargo +nightly doc --all-features  --open

the old way

cargo +nightly doc --all-features --config 'build.rustdocflags=["--cfg", "docsrs", "--generate-link-to-definition"]' --open

does not work anymore for some reason.