Crate readme_sync[][src]

Expand description

The readme-sync crate makes it easy to add an integration test that checks that your readme and crate documentation are synchronized.


This crate provides several abstractions for readme and documentation front page content as well as multiple readme and documentation parsing and transformation functions. With them, readme and documentation can be converted to a set of markup nodes that are expected to be the same. Their equality can be checked with the assert_sync function, which also provides useful diagnostic messages about the differences found.

Documentation parser accepts not only inner doc-comments (//!) but also inner doc-attributes (#[!cfg(...)] and #[!cfg_attr(...)]). This is useful when some doc-tests require certain features to compile and run.


First, add the following to your Cargo.toml:

readme-sync = "0.2.1"

Then add an integration test using the necessary readme and docs modifiers, and check their synchronization using the assert_sync function.

The example below is used to test the synchronization of the readme and documentation of this crate. You can copy it and follow the diagnostic messages to adjust the modifiers used and to correct your readme and documentation.

fn readme_sync_test() {
    use readme_sync::{assert_sync, CMarkDocs, CMarkReadme, Config, Package};
    use std::borrow::ToOwned;

    let package = Package::from_path(env!("CARGO_MANIFEST_DIR").into()).unwrap();
    let config = Config::from_package_docs_rs_features(&package);
    let readme = CMarkReadme::from_package(&package).unwrap();
    let docs = CMarkDocs::from_package_and_config(&package, &config).unwrap();

    let readme = readme

    let docs = docs
            |link| match link {
                "CMarkDocs::map_links" => "struct.CMarkDocs.html#method.map_links".into(),
                link => link.into(),
            "workaround for intra-doc links",

    assert_sync(&readme, &docs);

Note that both cargo build and cargo test enable features from dev-dependencies, so if you want to test your crate without them (for example in no_std environment) you can use readme-sync with default-features = false. See this FAQ section for more details.

Feature Flags

  • codemap (enabled by default): Enables codemap dependency and required for assert_sync and other diagnostic functions.
  • codemap-diagnostic (enabled by default): Enables codemap-diagnostic dependency and required for assert_sync and other diagnostic functions.
  • glob (enabled by default): Enables gloc dependency and required for badges detection and methods like CMarkReadme::remove_badges_paragraph.
  • platforms: Enables platforms dependency and method Config::with_target_arch_os_env.
  • proc-macro2 (enabled by default): Enables proc-macro2 dependency with span-locations feature that allows the crate to show the errors location for source Rust files.
  • pulldown-cmark (enabled by default): Enables pulldown-cmark dependency and required for almost everything except manifest and documentation parsing and some utility functions.
  • serde (enabled by default): Enables serde dependency and required for manifest deserializing.
  • syn (enabled by default): Enables syn dependency and required for documentation parsing.
  • thiserror (enabled by default): Enables thiserror dependency and required by all functions and methods that can return errors.
  • toml (enabled by default): Enables toml dependency and required for manifest parsing.

Other crates

  • cargo-sync-readme: generates readme section from documentation. It does not support doc-attributes and does not provide diagnostics for differences found. But if you just need to synchronize readme and docs text or check if they are synchronized it might be a better choice.
  • version-sync: crate makes it easy to add an integration test that checks that and documentation are updated when the crate version changes.


Currently intra-doc link resolution is not supported. References to structures in the documentation can be changed with CMarkDocs::map_links. The pulldown cmark also requires the link address to be specified.

Why is the example integration test so long and there is no function that would do it all at once?

Readme and documentation transformations are very different between different crates and the API of this crate is not yet stabilized.

At the moment, however, it supports extensive customization. You can specify the paths to readme and docs, their contents, the features and transformations used, and use your own transformations.

So any feedback is welcome!

Why use syn instead of just parsing documentation comments?

Because of cfg and cfg_attr that are useful for documentation tests that require some specific features and can only be compiled with them.

Why Markdown instead of text comparison?

It simplifies the Markdown transformations. Transformations are necessary, because of some differences between readme content and documentation front page including: the presence of a crate name, different heading levels, the presence of badges, different relative url root, etc.

Why are all dependencies optional?

By default, Rust compiler enables features from dev-dependencies for normal dependencies for commands like cargo test and cargo build. As a result, the features used by dev-dependencies are implicitly enabled during testing. Because all readme-sync dependencies are optional, you can easily protect your crate from implicitly enabled common features when testing.

See rust-lang/cargo#7916 for more details.

How to prevent readme-sync dependency features enabled for dependencies of my crate.

If you use nightly Rust you can simply use -Z features=dev_dep flags.

Or, in any Rust release, you can disable all readme-sync dependencies with:

version = "0.2.1"
default-features = false

This will help you avoid feature injection from dev-dependencies.

In order to use readme-sync functionality in this case, you need to add a feature that reenables readme-sync default features and can be used to run readme synchronization integration tests:

test-readme-sync = ["readme-sync/default"]

Then you need to add test-readme-sync conditional check to your readme sync integration test:

#[cfg(all(test, feature = "test-readme-sync"))]
//    ^^^^    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
fn readme_sync_test() {
    // ...

And run it with

cargo test --features "test-readme-sync"


Licensed under either of

at your option.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


A CMarkItems container storing a list of events with multiple transformation functions.

Parsed documentation Markdown with optionally specified package path and package manifest.

Parsed readme Markdown with optionally specified package path and package manifest.

Event’s region of source text.

Storage for codemap and corresponding codemap files.

Codemap span labels temporary storage used to create diagnostic messages.

A set of enabled named and key-value configuration options.

Parsed documentation text chunk.

Documentation text chunk span start and end.

File path and its contents.

Parsed .rs file documentation.

Package manifest.

Package manifest [[bin]] section.

Manifest metadata that customize builds.

Package manifest [lib] section.

Package manifest [package] section.

Readme and docs match failed diagnostics and codemap files.

A struct contains package manifest and its root path.

The pair of a source and the corresponding target text remap range.


An error which can occur when locating the binary file path by the specified target name.

An error which can occur when building documentation from attribute.

An error which can occur when building documentation from meta-attribute.

An enum that store Markdown event, its origin, and modifications. The event modification tree is stored to improve error messages.

An error which can occur when creating readme from package.

An error which can occur when checking readme and docs for equality.

An error which can occur when checking for disallowed link prefixes.

An error which can occur when evaluating configuration predicate.

An error which can occur when creating file documentation form a given file.

An error which can occur when reading a file from the specified path.

The optional Manifest readme field that allows string or boolean value.

Markdown parser text source which may be either readme file contents or package target parsed documentation.

An error which can occur when parsing manifest from toml file.

An error which can occur when reading manifest from the specified file path.


A helper trait to create an event as modified from other events.

A helper trait to mark events as removed.

A helper trait to mark an event with the specified note.


Asserts that the given readme and docs are the same.

Returns a Vec of populatar badge url patterns.

Builds documentation from the specified attribute.

Builds documentation from the specified compile-time structured attribute.

Returns Ok(()) if the given readme and docs are the same, and Err(CheckSyncError) otherwise.

Returns a slice of currently known tags used by cargo test in Markdown fenced code blocks.

Evaluates configuration predicate.

Type Definitions

A CMarkItems container iterator.