Sphinxcontrib-rust

This is a Sphinx extension for integrating Rust programming language projects in Sphinx builds. It will work with existing Rust docstrings with some minor tweaks. See Compatibility with rustdoc for writing docstrings compatible with both rustdoc and this extension. See Limitations for known limitations compared to rustdoc.

You can also read this documentation on Gitlab Pages or readthedocs.

Motivation

This is primarily meant for teams and projects that are already using Sphinx as a documentation build tool, and would like to include documentation for Rust projects in it along with Python, C, and other languages.

Using the extension adds the following functionality:

Rust specific directives and roles that can be used to define and link to Rust items.
rustdoc comments may be written in reStructuredText.
Various Sphinx features and extensions can be used to generate and publish the docs.

This is not a replacement for rustdoc, and since rustdoc is a part of the Rust language itself, it will not have all the same features as rustdoc.

The goal is to provide a way for teams and projects using multiple languages to publish a single, consolidated documentation and use this, along with rustdoc, as part of the documentation workflow.

See Limitations for some cases where the tool will not work the same as rustdoc and Compatibility with rustdoc for any tweaks required to make the tool work with existing docstrings.

Installation

There are two components that are required for this to work

The sphinx-rustdocgen Rust crate for extracting the docs.
The sphinxcontrib_rust Python package, which is a Sphinx extension.

Both components are installed when installing the Python package with

pip install sphinxcontrib-rust

The installation will check for cargo in the $PATH environment variable and will use that to build and install the Rust executable.

The executable is built with the Rust code shipped with the Python package to ensure that the Rust executable and Python package are always compatible with each other.

Make sure that the directory where cargo installs the executable is in $PATH as well. If the default installation directory is not part of the $PATH environment, the installed executable may be specified in the Sphinx configuration with rust_rustdocgen option.

If for any reason the crate does not get installed with Python package, it can be installed directly from crates.io with cargo install sphinx-rustdocgen. Make sure to install the same version of the create as the Python package.

Configuration

rustdoc compatible Markdown docstrings

This is most probably what you want to do and allows generating Sphinx documentation separately from rustdoc output.

To use the extension along with rustdoc, add the extension to Sphinx’s conf.py file and also add the myst-parser extension. Sphinx also needs to be configured for Markdown builds. Use the code snippet below with your crates specified in rust_crates to enable all if this.

Using various extensions for myst-parser, existing docstrings can be rendered with Sphinx with minimal changes. See Compatibility with rustdoc for details on how to write docstrings that can work with both rustdoc and Sphinx.

extensions = ["sphinxcontrib_rust", "myst_parser"]
source_suffix = {
    ".rst": "restructuredtext",
    ".md": "markdown",
    ".txt": "markdown", # Optional
}
# See docs/compatibility for details on these extensions.
myst_enable_extensions = {
    "attrs_block",
    "colon_fence",
    "html_admonition",
    "replacements",
    "smartquotes",
    "strikethrough",
    "tasklist",
}
rust_crates = {
    "my_crate": ".",
    "my_crate_derive": "my-crate-derive",
}
rust_doc_dir = "docs/crates/"
rust_rustdoc_fmt = "md"

This will generate the documentation from your Rust crates and put them in the docs/crates/<crate_name> directories. Including the docs in the Sphinx build describes the various ways to integrate the documentation in the Sphinx build. The Rust items can then be referenced using Rust specific roles from other docs in the Sphinx build.

See the configuration options for MyST for other options that are supported by myst-parser. They can be changed as required to customize the generated docs.

reStructuredText docstrings

Using the extension, it is also possible to write the Rust docstrings in reStructuredText. Note that this makes the docstrings unusable with Rustdoc and should only be considered when the rustdoc documentation will not be used. Publishing a crate with such docstrings is still possible, but the documentation on docs.rs for the crate will not be rendered properly.

To enable RST docstrings, add the extension to the conf.py file and configure it appropriately.

extensions = ["sphinxcontrib_rust"]
rust_crates = {
    "my_crate": ".",
    "my_crate_derive": "my-crate-derive",
}
rust_doc_dir = "docs/crates/"
rust_rustdoc_fmt = "rst"

This will generate the documentation from your Rust crates and put them in the docs/crates/<crate_name> directories. You can link against the documentation in your toctree by specifying the path to lib file and any executables. See Including the docs in the Sphinx build for more details. The Rust items can then be referenced using Rust specific roles from other docs in the Sphinx build.

Recommendations

Use a HTML theme that allows expanding the TOC in the sidebar completely. For example, if using sphinx_rtd_theme, set the navigation_depth in html_theme_options to -1 in the conf.py file (html_theme_options = {"navigation_depth": -1}). This makes the sidebar much better to use.
It is possible to write docstrings in Markdown and other documentation in reStructuredText. The configuration should be the same as what is described in rustdoc compatible Markdown docstrings. The roles and directives will work the same regardless of the choice of the docstrings syntax.

Options

Options are simply Python variables set in the conf.py file. Most options can be provided as a global value or a dict of values per crate, with the crate name as the key. The options that are global only are listed separately below.

rust_crates:: (Required) A dict of crate names and their source code directories. This must be a dict even for a single crate. It determines which crates are documented. The directory should be the one which contains the Cargo.toml file for the crate and each crate in the workspace must be listed explicitly.
rust_doc_dir:: (Required) A directory under which to write the docs for all crates, or a dict of directory for each crate name. The directories will be read by Sphinx during the build, so they must be part of the source tree and not under the build directory. The build process will create a directory with the crate name under this, even when specified per crate.
rust_rustdoc_fmt:: Either rst or md. (Default: rst)
rust_visibility:: Only includes documentation and indexes for items with visibility greater than or equal to the setting. The value can be pub, crate or pvt. Visibility restrictions like super and in <path> are not supported currently and are treated as private. (Default: pub).
rust_strip_src:: Whether to remove the src/ directory when creating output files or not. The default is True, since that was the initial behavior. So, instead of creating output files as <crate_name>/src/<mod_name>.rst, the output files are created as <crate_name>/<mod_name>.rst, effectively removing src/ from the paths. Set to False for crates that use a different path. (Default: True)

The below options are global options, and cannot be specified per crate.

rust_generate_mode:: One of always, skip or changed. If set to always, all documents are regenerated. If set to skip, the docs are not regenerated at all. If set to changed, only docs whose source files have been modified since they were last modified are regenerated. (Default: changed)
rust_rustdocgen:: The path to the sphinx-rustdocgen executable to use. The path must be an absolute path or relative to Sphinx’s working directory. (Default: Obtained from the $PATH environment variable.)