cargo public-api command

You might want the convenient cargo public-api wrapper for this library. See https://github.com/Enselic/cargo-public-api.

public-api

List and diff the public API of Rust library crates by analyzing their rustdoc JSON. Diffing the public API between releases and commits can help you find breaking API changes and semver violations.

Usage

The library comes with a thin bin wrapper that can be used to explore the capabilities of this library.

# Build and install the thin bin wrapper with the a recent stable Rust toolchain
cargo install public-api

# Install nightly-2022-03-14 or later so you can build up-to-date rustdoc JSON files
rustup install nightly

List public API

To list all items that form the public API of your Rust library:

# Generate rustdoc JSON for your own Rust library
% cd ~/src/your_library
% RUSTDOCFLAGS='-Z unstable-options --output-format json' cargo +nightly doc --lib --no-deps

# List all items in the public API of your Rust library
% public-api ./target/doc/your_library.json
pub mod public_api
pub fn public_api::Options::clone(&self) -> Options
pub fn public_api::Options::default() -> Self
pub fn public_api::PublicItem::clone(&self) -> PublicItem
pub fn public_api::public_api_from_rustdoc_json_str(rustdoc_json_str: &str, options: Options) -> Result<Vec<PublicItem>>
pub struct public_api::Options
pub struct public_api::PublicItem
pub struct field public_api::Options::sorted: bool
pub struct field public_api::Options::with_blanket_implementations: bool
...

Diff public API

It is frequently of interest to know how the public API of a crate has changed. You can find this out by doing a diff between different versions of the same library. Again, cargo public-api makes this more convenient, but it is straightforward enough without it.

# Generate two different rustdoc JSON files for two different versions of your library
# and then pass both files to the bin to make it print the public API diff
% public-api ./target/doc/your_library.old.json  ./target/doc/your_library.json
Removed:
(nothing)

Changed:
-pub fn public_api::sorted_public_api_from_rustdoc_json_str(rustdoc_json_str: &str) -> Result<Vec<PublicItem>>
+pub fn public_api::sorted_public_api_from_rustdoc_json_str(rustdoc_json_str: &str, options: Options) -> Result<Vec<PublicItem>>

Added:
+pub fn public_api::Options::clone(&self) -> Options
+pub fn public_api::Options::default() -> Self
+pub struct public_api::Options
+pub struct field public_api::Options::with_blanket_implementations: bool

Expected output

In general, output aims to be character-by-character identical to the textual parts of the regular cargo doc HTML output. For example, this item has the following textual representation in the rendered HTML:

pub fn input_files<I, P>(&mut self, paths: I) -> &mut Self
where
    I: IntoIterator<Item = P>,
    P: AsRef<Path>,

and public-api represent this item in the following manner:

pub fn bat::PrettyPrinter::input_files<I, P>(&mut self, paths: I) -> &mut Self where I: IntoIterator<Item = P>, P: AsRef<Path>

If we normalize by removing newline characters and adding some whitespace padding to get the alignment right for side-by-side comparison, we can see that they are exactly the same, except an irrelevant trailing comma:

pub fn                     input_files<I, P>(&mut self, paths: I) -> &mut Self where I: IntoIterator<Item = P>, P: AsRef<Path>,
pub fn bat::PrettyPrinter::input_files<I, P>(&mut self, paths: I) -> &mut Self where I: IntoIterator<Item = P>, P: AsRef<Path>

Blanket implementations

By default, blanket implementations such as impl<T> Any for T, impl<T> Borrow<T> for T, and impl<T, U> Into<U> for T where U: From<T> are omitted from the list of public items of a crate. For the vast majority of use cases, blanket implementations are not of interest, and just creates noise.

If you want to include items of blanket implementations in the output, set Options::with_blanket_implementations to true if you use the library, or pass --with-blanket-implementations to public_api.

Library documentation

Documentation can be found at docs.rs as usual. There are also some simple examples on how to use the library. The code for the thin bin wrapper might also be of interest.

Target audience

Maintainers of Rust libraries that want to keep track of changes to their public API.

Limitations

See [limitation] labeled issues.

Compatibility matrix

Development

See development.md.