rust/tests/rustdoc/auxiliary/html_root.rs

#![doc(html_root_url="https://example.com/html_root")]
pub fn foo() {}
Give precedence to `html_root_url` over `--extern-html-root-url` by default, but add a way to opt-in to the previous behavior ## What is an HTML root url? It tells rustdoc where it should link when documentation for a crate is not available locally; for example, when a crate is a dependency of a crate documented with `cargo doc --no-deps`. ## What is the difference between `html_root_url` and `--extern-html-root-url`? Both of these tell rustdoc what the HTML root should be set to. `doc(html_root_url)` is set by the crate author, while `--extern-html-root-url` is set by the person documenting the crate. These are often different. For example, docs.rs uses `--extern-html-root-url https://docs.rs/crate-name/version` to ensure all crates have documentation, even if `html_root_url` is not set. Conversely, crates such as Rocket set `doc(html_root_url = "https://api.rocket.rs")`, because they prefer users to view the documentation on their own site. Crates also set `html_root_url` to ensure they have documentation when building locally when offline. This is unfortunate to require, because it's more work from the library author. It also makes it impossible to distinguish between crates that want to be viewed on a different site (e.g. Rocket) and crates that just want documentation to be visible offline at all (e.g. Tokio). I have authored a separate change to the API guidelines to no longer recommend doing this: https://github.com/rust-lang/api-guidelines/pull/230. ## Why change the default? In the past, docs.rs has been the main user of `--extern-html-root-url`. However, it's useful for other projects as well. In particular, Cargo wants to pass it by default when running `--no-deps` (https://github.com/rust-lang/cargo/issues/8296). Unfortunately, for these other use cases, the priority order is inverted. They want to give precedence to the URL the crate picks, and only fall back to the `--extern-html-root` if no `html_root_url` is present. That allows passing `--extern-html-root` unconditionally, without having to parse the source code to see what attributes are present. For docs.rs, however, we still want to keep the old behavior, so that all links on docs.rs stay on the site. 2021-03-04 20:03:22 +00:00			`#![doc(html_root_url="https://example.com/html_root")]`
			`pub fn foo() {}`