276 lines
9.6 KiB
Markdown
276 lines
9.6 KiB
Markdown
Blackfriday [](https://travis-ci.org/russross/blackfriday) [](https://godoc.org/github.com/russross/blackfriday)
|
|
===========
|
|
|
|
Blackfriday is a [Markdown][1] processor implemented in [Go][2]. It
|
|
is paranoid about its input (so you can safely feed it user-supplied
|
|
data), it is fast, it supports common extensions (tables, smart
|
|
punctuation substitutions, etc.), and it is safe for all utf-8
|
|
(unicode) input.
|
|
|
|
HTML output is currently supported, along with Smartypants
|
|
extensions. An experimental LaTeX output engine is also included.
|
|
|
|
It started as a translation from C of [Sundown][3].
|
|
|
|
|
|
Installation
|
|
------------
|
|
|
|
Blackfriday is compatible with Go 1. If you are using an older
|
|
release of Go, consider using v1.1 of blackfriday, which was based
|
|
on the last stable release of Go prior to Go 1. You can find it as a
|
|
tagged commit on github.
|
|
|
|
With Go 1 and git installed:
|
|
|
|
go get github.com/russross/blackfriday
|
|
|
|
will download, compile, and install the package into your `$GOPATH`
|
|
directory hierarchy. Alternatively, you can achieve the same if you
|
|
import it into a project:
|
|
|
|
import "github.com/russross/blackfriday"
|
|
|
|
and `go get` without parameters.
|
|
|
|
Usage
|
|
-----
|
|
|
|
For basic usage, it is as simple as getting your input into a byte
|
|
slice and calling:
|
|
|
|
output := blackfriday.MarkdownBasic(input)
|
|
|
|
This renders it with no extensions enabled. To get a more useful
|
|
feature set, use this instead:
|
|
|
|
output := blackfriday.MarkdownCommon(input)
|
|
|
|
### Sanitize untrusted content
|
|
|
|
Blackfriday itself does nothing to protect against malicious content. If you are
|
|
dealing with user-supplied markdown, we recommend running blackfriday's output
|
|
through HTML sanitizer such as
|
|
[Bluemonday](https://github.com/microcosm-cc/bluemonday).
|
|
|
|
Here's an example of simple usage of blackfriday together with bluemonday:
|
|
|
|
``` go
|
|
import (
|
|
"github.com/microcosm-cc/bluemonday"
|
|
"github.com/russross/blackfriday"
|
|
)
|
|
|
|
// ...
|
|
unsafe := blackfriday.MarkdownCommon(input)
|
|
html := bluemonday.UGCPolicy().SanitizeBytes(unsafe)
|
|
```
|
|
|
|
### Custom options
|
|
|
|
If you want to customize the set of options, first get a renderer
|
|
(currently either the HTML or LaTeX output engines), then use it to
|
|
call the more general `Markdown` function. For examples, see the
|
|
implementations of `MarkdownBasic` and `MarkdownCommon` in
|
|
`markdown.go`.
|
|
|
|
You can also check out `blackfriday-tool` for a more complete example
|
|
of how to use it. Download and install it using:
|
|
|
|
go get github.com/russross/blackfriday-tool
|
|
|
|
This is a simple command-line tool that allows you to process a
|
|
markdown file using a standalone program. You can also browse the
|
|
source directly on github if you are just looking for some example
|
|
code:
|
|
|
|
* <http://github.com/russross/blackfriday-tool>
|
|
|
|
Note that if you have not already done so, installing
|
|
`blackfriday-tool` will be sufficient to download and install
|
|
blackfriday in addition to the tool itself. The tool binary will be
|
|
installed in `$GOPATH/bin`. This is a statically-linked binary that
|
|
can be copied to wherever you need it without worrying about
|
|
dependencies and library versions.
|
|
|
|
|
|
Features
|
|
--------
|
|
|
|
All features of Sundown are supported, including:
|
|
|
|
* **Compatibility**. The Markdown v1.0.3 test suite passes with
|
|
the `--tidy` option. Without `--tidy`, the differences are
|
|
mostly in whitespace and entity escaping, where blackfriday is
|
|
more consistent and cleaner.
|
|
|
|
* **Common extensions**, including table support, fenced code
|
|
blocks, autolinks, strikethroughs, non-strict emphasis, etc.
|
|
|
|
* **Safety**. Blackfriday is paranoid when parsing, making it safe
|
|
to feed untrusted user input without fear of bad things
|
|
happening. The test suite stress tests this and there are no
|
|
known inputs that make it crash. If you find one, please let me
|
|
know and send me the input that does it.
|
|
|
|
NOTE: "safety" in this context means *runtime safety only*. In order to
|
|
protect yourself against JavaScript injection in untrusted content, see
|
|
[this example](https://github.com/russross/blackfriday#sanitize-untrusted-content).
|
|
|
|
* **Fast processing**. It is fast enough to render on-demand in
|
|
most web applications without having to cache the output.
|
|
|
|
* **Thread safety**. You can run multiple parsers in different
|
|
goroutines without ill effect. There is no dependence on global
|
|
shared state.
|
|
|
|
* **Minimal dependencies**. Blackfriday only depends on standard
|
|
library packages in Go. The source code is pretty
|
|
self-contained, so it is easy to add to any project, including
|
|
Google App Engine projects.
|
|
|
|
* **Standards compliant**. Output successfully validates using the
|
|
W3C validation tool for HTML 4.01 and XHTML 1.0 Transitional.
|
|
|
|
|
|
Extensions
|
|
----------
|
|
|
|
In addition to the standard markdown syntax, this package
|
|
implements the following extensions:
|
|
|
|
* **Intra-word emphasis supression**. The `_` character is
|
|
commonly used inside words when discussing code, so having
|
|
markdown interpret it as an emphasis command is usually the
|
|
wrong thing. Blackfriday lets you treat all emphasis markers as
|
|
normal characters when they occur inside a word.
|
|
|
|
* **Tables**. Tables can be created by drawing them in the input
|
|
using a simple syntax:
|
|
|
|
```
|
|
Name | Age
|
|
--------|------
|
|
Bob | 27
|
|
Alice | 23
|
|
```
|
|
|
|
* **Fenced code blocks**. In addition to the normal 4-space
|
|
indentation to mark code blocks, you can explicitly mark them
|
|
and supply a language (to make syntax highlighting simple). Just
|
|
mark it like this:
|
|
|
|
``` go
|
|
func getTrue() bool {
|
|
return true
|
|
}
|
|
```
|
|
|
|
You can use 3 or more backticks to mark the beginning of the
|
|
block, and the same number to mark the end of the block.
|
|
|
|
To preserve classes of fenced code blocks while using the bluemonday
|
|
HTML sanitizer, use the following policy:
|
|
|
|
``` go
|
|
p := bluemonday.UGCPolicy()
|
|
p.AllowAttrs("class").Matching(regexp.MustCompile("^language-[a-zA-Z0-9]+$")).OnElements("code")
|
|
html := p.SanitizeBytes(unsafe)
|
|
```
|
|
|
|
* **Definition lists**. A simple definition list is made of a single-line
|
|
term followed by a colon and the definition for that term.
|
|
|
|
Cat
|
|
: Fluffy animal everyone likes
|
|
|
|
Internet
|
|
: Vector of transmission for pictures of cats
|
|
|
|
Terms must be separated from the previous definition by a blank line.
|
|
|
|
* **Footnotes**. A marker in the text that will become a superscript number;
|
|
a footnote definition that will be placed in a list of footnotes at the
|
|
end of the document. A footnote looks like this:
|
|
|
|
This is a footnote.[^1]
|
|
|
|
[^1]: the footnote text.
|
|
|
|
* **Autolinking**. Blackfriday can find URLs that have not been
|
|
explicitly marked as links and turn them into links.
|
|
|
|
* **Strikethrough**. Use two tildes (`~~`) to mark text that
|
|
should be crossed out.
|
|
|
|
* **Hard line breaks**. With this extension enabled (it is off by
|
|
default in the `MarkdownBasic` and `MarkdownCommon` convenience
|
|
functions), newlines in the input translate into line breaks in
|
|
the output.
|
|
|
|
* **Smart quotes**. Smartypants-style punctuation substitution is
|
|
supported, turning normal double- and single-quote marks into
|
|
curly quotes, etc.
|
|
|
|
* **LaTeX-style dash parsing** is an additional option, where `--`
|
|
is translated into `–`, and `---` is translated into
|
|
`—`. This differs from most smartypants processors, which
|
|
turn a single hyphen into an ndash and a double hyphen into an
|
|
mdash.
|
|
|
|
* **Smart fractions**, where anything that looks like a fraction
|
|
is translated into suitable HTML (instead of just a few special
|
|
cases like most smartypant processors). For example, `4/5`
|
|
becomes `<sup>4</sup>⁄<sub>5</sub>`, which renders as
|
|
<sup>4</sup>⁄<sub>5</sub>.
|
|
|
|
|
|
Other renderers
|
|
---------------
|
|
|
|
Blackfriday is structured to allow alternative rendering engines. Here
|
|
are a few of note:
|
|
|
|
* [github_flavored_markdown](https://godoc.org/github.com/shurcooL/github_flavored_markdown):
|
|
provides a GitHub Flavored Markdown renderer with fenced code block
|
|
highlighting, clickable header anchor links.
|
|
|
|
It's not customizable, and its goal is to produce HTML output
|
|
equivalent to the [GitHub Markdown API endpoint](https://developer.github.com/v3/markdown/#render-a-markdown-document-in-raw-mode),
|
|
except the rendering is performed locally.
|
|
|
|
* [markdownfmt](https://github.com/shurcooL/markdownfmt): like gofmt,
|
|
but for markdown.
|
|
|
|
* LaTeX output: renders output as LaTeX. This is currently part of the
|
|
main Blackfriday repository, but may be split into its own project
|
|
in the future. If you are interested in owning and maintaining the
|
|
LaTeX output component, please be in touch.
|
|
|
|
It renders some basic documents, but is only experimental at this
|
|
point. In particular, it does not do any inline escaping, so input
|
|
that happens to look like LaTeX code will be passed through without
|
|
modification.
|
|
|
|
* [Md2Vim](https://github.com/FooSoft/md2vim): transforms markdown files into vimdoc format.
|
|
|
|
|
|
Todo
|
|
----
|
|
|
|
* More unit testing
|
|
* Improve unicode support. It does not understand all unicode
|
|
rules (about what constitutes a letter, a punctuation symbol,
|
|
etc.), so it may fail to detect word boundaries correctly in
|
|
some instances. It is safe on all utf-8 input.
|
|
|
|
|
|
License
|
|
-------
|
|
|
|
[Blackfriday is distributed under the Simplified BSD License](LICENSE.txt)
|
|
|
|
|
|
[1]: http://daringfireball.net/projects/markdown/ "Markdown"
|
|
[2]: http://golang.org/ "Go Language"
|
|
[3]: https://github.com/vmg/sundown "Sundown"
|