diff --git a/src/doc/rustdoc/src/SUMMARY.md b/src/doc/rustdoc/src/SUMMARY.md index b512135d927..12a8b2b8db4 100644 --- a/src/doc/rustdoc/src/SUMMARY.md +++ b/src/doc/rustdoc/src/SUMMARY.md @@ -7,6 +7,7 @@ - [How to write documentation](how-to-write-documentation.md) - [What to include (and exclude)](write-documentation/what-to-include.md) - [The `#[doc]` attribute](write-documentation/the-doc-attribute.md) + - [Re-exports](write-documentation/re-exports.md) - [Linking to items by name](write-documentation/linking-to-items-by-name.md) - [Documentation tests](write-documentation/documentation-tests.md) - [Rustdoc-specific lints](lints.md) diff --git a/src/doc/rustdoc/src/write-documentation/re-exports.md b/src/doc/rustdoc/src/write-documentation/re-exports.md new file mode 100644 index 00000000000..593428b8a70 --- /dev/null +++ b/src/doc/rustdoc/src/write-documentation/re-exports.md @@ -0,0 +1,172 @@ +# Re-exports + +Let's start by explaining what are re-exports. To do so, we will use an example where we are +writing a library (named `lib`) with some types dispatched in sub-modules: + +```rust +pub mod sub_module1 { + pub struct Foo; +} +pub mod sub_module2 { + pub struct AnotherFoo; +} +``` + +Users can import them like this: + +```rust,ignore (inline) +use lib::sub_module1::Foo; +use lib::sub_module2::AnotherFoo; +``` + +But what if you want the types to be available directly at the crate root or if we don't want the +modules to be visible for users? That's where re-exports come in: + +```rust,ignore (inline) +// `sub_module1` and `sub_module2` are not visible outside. +mod sub_module1 { + pub struct Foo; +} +mod sub_module2 { + pub struct AnotherFoo; +} +// We re-export both types: +pub use crate::sub_module1::Foo; +pub use crate::sub_module2::AnotherFoo; +``` + +And now users will be able to do: + +```rust,ignore (inline) +use lib::{Foo, AnotherFoo}; +``` + +And since both `sub_module1` and `sub_module2` are private, users won't be able to import them. + +Now what's interesting is that the generated documentation for this crate will show both `Foo` and +`AnotherFoo` directly at the crate root, meaning they have been inlined. There are a few rules to +know whether or not a re-exported item will be inlined. + +## Inlining rules + +If a public item comes from a private module, it will be inlined: + +```rust,ignore (inline) +mod private_module { + pub struct Public; +} +pub mod public_mod { + // `Public` will inlined here since `private_module` is private. + pub use super::private_module::Public; +} +// `Public` will not be inlined here since `public_mod` is public. +pub use self::public_mod::Public; +``` + +Likewise, if an item inherits `#[doc(hidden)]` from any of its ancestors, it will be inlined: + +```rust,ignore (inline) +#[doc(hidden)] +pub mod public_mod { + pub struct Public; +} +// `Public` be inlined since its parent (`public_mod`) has `#[doc(hidden)]`. +pub use self::public_mod::Public; +``` + +If an item has `#[doc(hidden)]`, it won't be inlined (nor visible in the generated documentation): + +```rust,ignore (inline) +// This struct won't be visible. +#[doc(hidden)] +pub struct Hidden; + +// This re-export won't be visible. +pub use self::Hidden as InlinedHidden; +``` + +The same applies on re-exports themselves: if you have multiple re-exports and some of them have +`#[doc(hidden)]`, then these ones (and only these) own't appear in the documentation: + +```rust,ignore (inline) +mod private_mod { + /// First + pub struct InPrivate; +} + +/// Second +#[doc(hidden)] +pub use self::private_mod::InPrivate as Hidden; +/// Third +pub use self::Hidden as Visible; +``` + +In this case, `InPrivate` will be inlined as `Visible`. However, its documentation will be +`First Third` and not `First Second Third` because the re-export with `Second` as documentation has +`#[doc(hidden)]`, therefore, all its attributes are ignored. + +## Inlining with `#[doc(inline)]` + +You can use the `#[doc(inline)]` attribute if you want to force an item to be inlined: + +```rust,ignore (inline) +pub mod public_mod { + pub struct Public; +} +#[doc(inline)] +pub use self::public_mod::Public; +``` + +With this code, even though `public_mod::Public` is public and present in the documentation, the +`Public` type will be present both at the crate root and in the `public_mod` module. + +## Preventing inlining with `#[doc(no_inline)]` + +On the opposite of the `#[doc(inline)]` attribute, if you want to prevent an item from being +inlined, you can use `#[doc(no_inline)]`: + +```rust,ignore (inline) +mod private_mod { + pub struct Public; +} +#[doc(no_inline)] +pub use self::private_mod::Public; +``` + +In the generated documentation, you will see a re-export at the crate root and not the type +directly. + +## Attributes + +When an item is inlined, its doc comments and most of its attributes will be inlined along with it: + +```rust,ignore (inline) +mod private_mod { + /// First + #[cfg(a)] + pub struct InPrivate; + /// Second + #[cfg(b)] + pub use self::InPrivate as Second; +} + +/// Third +#[doc(inline)] +#[cfg(c)] +pub use self::private_mod::Second as Visible; +``` + +In this case, `Visible` will have as documentation `First Second Third` and will also have as `cfg`: +`#[cfg(a, b, c)]`. + +[Intra-doc links](./linking-to-items-by-name.md) are resolved relative to where the doc comment is +defined. + +There are a few attributes which are not inlined though: + * `#[doc(alias="")]` + * `#[doc(inline)]` + * `#[doc(no_inline)]` + * `#[doc(hidden)]` (because the re-export itself and its attributes are ignored). + +All other attributes are inherited when inlined, so that the documentation matches the behavior if +the inlined item was directly defined at the spot where it's shown. diff --git a/src/doc/rustdoc/src/write-documentation/the-doc-attribute.md b/src/doc/rustdoc/src/write-documentation/the-doc-attribute.md index 8ecf05f0e12..046d018543f 100644 --- a/src/doc/rustdoc/src/write-documentation/the-doc-attribute.md +++ b/src/doc/rustdoc/src/write-documentation/the-doc-attribute.md @@ -223,12 +223,18 @@ Now we'll have a `Re-exports` line, and `Bar` will not link to anywhere. One special case: In Rust 2018 and later, if you `pub use` one of your dependencies, `rustdoc` will not eagerly inline it as a module unless you add `#[doc(inline)]`. +If you want to know more about inlining rules, take a look at the +[`re-exports` chapter](./re-exports.md). + ### `hidden` Any item annotated with `#[doc(hidden)]` will not appear in the documentation, unless -the `strip-hidden` pass is removed. +the `strip-hidden` pass is removed. Re-exported items where one of its ancestors has +`#[doc(hidden)]` will be considered the same as private. + +You can find more information in the [`re-exports` chapter](./re-exports.md). ### `alias`