  [](https://opencollective.com/comrak)
[](https://crates.io/crates/comrak)
[](https://docs.rs/comrak)
Rust port of [github's `cmark-gfm`](https://github.com/github/cmark).
- [Installation](#installation)
- [Usage](#usage)
- [Security](#security)
- [Extensions](#extensions)
- [Related projects](#related-projects)
- [Contributing](#contributing)
- [Legal](#legal)
## Installation
Specify it as a requirement in `Cargo.toml`:
``` toml
[dependencies]
comrak = "0.8"
```
Comrak supports Rust stable.
## Usage
A binary is included which does everything you typically want:
``` console
$ comrak --help
comrak 0.8.0
Ashe Connor <ashe@kivikakk.ee>
A 100% CommonMark-compatible GitHub Flavored Markdown parser and formatter
USAGE:
comrak [FLAGS] [OPTIONS] [--] [FILE]...
FLAGS:
--gfm Enable GitHub-flavored markdown extensions strikethrough, tagfilter, table, autolink, and
tasklist. It also enables --github-pre-lang.
--github-pre-lang Use GitHub-style <pre lang> for code blocks
--hardbreaks Treat newlines as hard line breaks
-h, --help Prints help information
--smart Use smart punctuation
--unsafe Allow raw HTML and dangerous URLs
-V, --version Prints version information
OPTIONS:
--default-info-string <INFO> Default value for fenced code block's info strings if none is given
-e, --extension <EXTENSION>... Specify an extension name to use [possible values: strikethrough, tagfilter,
table, autolink, tasklist, superscript, footnotes, description-lists]
-t, --to <FORMAT> Specify output format [default: html] [possible values: html, commonmark]
--header-ids <PREFIX> Use the Comrak header IDs extension, with the given ID prefix
--width <WIDTH> Specify wrap width (0 = nowrap) [default: 0]
ARGS:
<FILE>... The CommonMark file to parse; or standard input if none passed
```
And there's a Rust interface. You can use `comrak::markdown_to_html` directly:
``` rust
use comrak::{markdown_to_html, ComrakOptions};
assert_eq!(markdown_to_html("Hello, **世界**!", &ComrakOptions::default()),
"<p>Hello, <strong>世界</strong>!</p>\n");
```
Or you can parse the input into an AST yourself, manipulate it, and then use your desired formatter:
``` rust
extern crate comrak;
use comrak::{parse_document, format_html, Arena, ComrakOptions};
use comrak::nodes::{AstNode, NodeValue};
// The returned nodes are created in the supplied Arena, and are bound by its lifetime.
let arena = Arena::new();
let root = parse_document(
&arena,
"This is my input.\n\n1. Also my input.\n2. Certainly my input.\n",
&ComrakOptions::default());
fn iter_nodes<'a, F>(node: &'a AstNode<'a>, f: &F)
where F : Fn(&'a AstNode<'a>) {
f(node);
for c in node.children() {
iter_nodes(c, f);
}
}
iter_nodes(root, &|node| {
match &mut node.data.borrow_mut().value {
&mut NodeValue::Text(ref mut text) => {
let orig = std::mem::replace(text, vec![]);
*text = String::from_utf8(orig).unwrap().replace("my", "your").as_bytes().to_vec();
}
_ => (),
}
});
let mut html = vec![];
format_html(root, &ComrakOptions::default(), &mut html).unwrap();
assert_eq!(
String::from_utf8(html).unwrap(),
"<p>This is your input.</p>\n\
<ol>\n\
<li>Also your input.</li>\n\
<li>Certainly your input.</li>\n\
</ol>\n");
```
## Security
As with [`cmark`](https://github.com/commonmark/cmark) and [`cmark-gfm`](https://github.com/github/cmark-gfm#security),
Comrak will scrub raw HTML and potentially dangerous links. This change was introduced in Comrak 0.4.0 in support of a
safe-by-default posture.
To allow these, use the `unsafe_` option (or `--unsafe` with the command line program). If doing so, we recommend the
use of a sanitisation library like [`ammonia`](https://github.com/notriddle/ammonia) configured specific to your needs.
## Extensions
Comrak supports the five extensions to CommonMark defined in the [GitHub Flavored Markdown
Spec](https://github.github.com/gfm/):
- [Tables](https://github.github.com/gfm/#tables-extension-)
- [Task list items](https://github.github.com/gfm/#task-list-items-extension-)
- [Strikethrough](https://github.github.com/gfm/#strikethrough-extension-)
- [Autolinks](https://github.github.com/gfm/#autolinks-extension-)
- [Disallowed Raw HTML](https://github.github.com/gfm/#disallowed-raw-html-extension-)
Comrak additionally supports its own extensions, which are yet to be specced out (PRs welcome\!):
- Superscript
- Header IDs
- Footnotes
- Description lists
By default none are enabled; they are individually enabled with each parse by setting the appropriate values in the
[`ComrakOptions` struct](https://docs.rs/comrak/newest/comrak/struct.ComrakOptions.html).
## Related projects
Comrak's design goal is to model the upstream [`cmark-gfm`](https://github.com/github/cmark-gfm) as closely as possible
in terms of code structure. The upside of this is that a change in `cmark-gfm` has a very predictable change in Comrak.
Likewise, any bug in `cmark-gfm` is likely to be reproduced in Comrak. This could be considered a pro or a con,
depending on your use case.
The downside, of course, is that the code is not what I'd call idiomatic Rust (*so many `RefCell`s*), and while
contributors and I have made it as fast as possible, it simply won't be as fast as some other CommonMark parsers
depending on your use-case. Here are some other projects to consider:
- [Raph Levien](https://github.com/raphlinus)'s [`pulldown-cmark`](https://github.com/google/pulldown-cmark). It's
very fast, uses a novel parsing algorithm, and doesn't construct an AST (but you can use it to make one if you
want). Recent `cargo doc` uses this, as do many other projects in the ecosystem. It's not quite at 100% spec
compatibility yet.
- [Ben Navetta](https://github.com/bnavetta)'s [`rcmark`](https://github.com/bnavetta/rcmark) is a set of bindings to
`libcmark`. It hasn't been updated in a while, though there's an [open pull
request](https://github.com/bnavetta/rcmark/pull/2).
- Know of another library? Please open a PR to add it\!
As far as I know, Comrak is the only library to implement all of the [GitHub Flavored Markdown
extensions](https://github.github.com/gfm) to the spec, but this tends to only be important if you want to reproduce
GitHub's Markdown rendering exactly, e.g. in a GitHub client app.
## Contributing
Contributions are highly encouraged; where possible I practice [Optimistic Merging](http://hintjens.com/blog:106) as
described by Peter Hintjens. Please keep the [code of conduct](CODE_OF_CONDUCT.md) in mind when interacting with this
project.
Thank you to comrak's many contributors for PRs and issues opened\!
### Code Contributors
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### Financial Contributors
Become a financial contributor and help us sustain our community.
\[[Contribute](https://opencollective.com/comrak/contribute)\]
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## Legal
Copyright (c) 2017–2020, Ashe Connor. Licensed under the [2-Clause BSD
License](https://opensource.org/licenses/BSD-2-Clause).
`cmark` itself is is copyright (c) 2014, John MacFarlane.
See [COPYING](COPYING) for all the details.