cargo sync-readme

A plugin that generates a Markdown section in your README based on your Rust documentation.

How does this work?

Basically, this tool provides you with a simple mechanism to synchronize your front page documentation from your lib.rs or main.rs with a place in your readme file. In order to do so, this command will parse your inner documentation (i.e. //!) on lib.rs or main.rs and will output it in your readme file at specific markers.

The markers

Because you might want a specific readme file that adds some more information to the documentation from your Rust code, this tool allows you to select a place where to put the documentation. This is done with three markers:

• <!-- cargo-sync-readme -->: that annotation must be placed in your readme file where you want the Rust documentation to be included and synchronized.
• <!-- cargo-sync-readme start -->: that annotation is automatically inserted by the command to delimit the beginning of the synchronized documentation.
• <!-- cargo-sync-readme end -->: that annotation is automatically inserted by the command to delimit the ending of the synchronized documentation.

You only have to use the former marker (i.e. <!-- cargo-sync-readme -->). The rest of the markers will be handled automatically for you by the tool.

Okay, but I want to change the place of the documentation now.

When you have already put the synchronized documentation in your readme but want to change its location, all you have to do is remove everything in between the start and end annotations (annotations included) and place the <!-- cargo-sync-readme --> annotation wherever you want your synchronized documentation to appear.

How should I use this?

First, this tool will respect what you put in your Cargo.toml. There is a special field called readme that gives the name / path of the document you want to use as readme file. cargo sync-readme will operate on that file.

Disclaimer: even though crates.io’s documentation and manifest format doesn’t explicitly state the type of this file, cargo sync-readme assumes it’s Markdown. If you want a support for another file type, please open an issue or a PR: those are warmly welcomed — and if you live in Paris, I offer you a Kwak or a Chouffe! ♥

Once you have put the annotation in your readme file, just run the command without argument to perform the synchronization:

cargo sync-readme

This will effectively update your readme file with the main documentation from your Rust code (either a lib.rs or main.rs, depending on the type of your crate).

Intra-link support

This tool rewrites intra-links so they point at the corresponding place in docs.rs. The intra-links must be of the form [⋯](crate::⋯).

Links to the standard library are also supported, and they must be of the form [⋯](<crate>::⋯), where <crate> is a crate that is part of the standard library, such as std, core, or alloc.

Please note that there are some limitations to intra-link support. To create the links we have to parse the source code to find out the class of the symbol being referenced (whether it is a struct, trait, etc). That necessarily imposes some restrictions, for instance, we will not expand macros so symbols defined in macros will not be linkable.

Switches and options

The command has several options and flags you can use to customize the experience (a bit like a Disneyland Parc experience, but less exciting).

• -z or --show-hidden-doc: this flag will disable a special transformation on your documentation when copying into the region you’ve selected in your readme. All ignored / hidden lines (the ones starting with a dash in code block in Rust doc) will simply be dropped by default. This might be wanted if you want your readme documentation to look like the one on docs.rs, where the hidden lines don’t show up. If you don’t, use this flag to disable this behavior.
• -f or --prefer-doc-from: this option allows you to override the place where to get the documentation from. This might be wanted to override the default behavior that reads from the Cargo.toml manifest, the autodetection based on files or when you have both a binary and library setup (in which case this option is mandatory).
• --crlf: this flag makes the tool’s newlines behaves according to CRLF. It will not change the already present newlines but expect your document to be formatted with CRLF. If it’s not then you will get punched in the face by a squirrel driving a motorcycle. Sorry. Also, it will generate newlines with CRLF.
• -c --check: check whether the readme is synchronized.

Q/A and troubleshooting

Are workspace crates supported?

Not yet! If you have ideas how the tool should behave with them, please contribute with an issue or a PR!