blackfriday/v2/README.md

Blackfriday
[![Build Status][BuildV2SVG]][BuildV2URL]
[![PkgGoDev][PkgGoDevV2SVG]][PkgGoDevV2URL]
===========

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.

It started as a translation from C of [Sundown][3].


Installation
------------

Blackfriday is compatible with modern Go releases in module mode.
With Go installed:

    go get github.com/russross/blackfriday/v2

will resolve and add the package to the current development module,
then build and install it. Alternatively, you can achieve the same
if you import it in a package:

    import "github.com/russross/blackfriday/v2"

and `go get` without parameters.

Legacy GOPATH mode is unsupported.


Versions
--------

Currently maintained and recommended version of Blackfriday is `v2`. It's being
developed on its own branch: https://github.com/russross/blackfriday/tree/v2 and the
documentation is available at
https://pkg.go.dev/github.com/russross/blackfriday/v2.

It is `go get`-able in module mode at `github.com/russross/blackfriday/v2`.

Version 2 offers a number of improvements over v1:

* Cleaned up API
* A separate call to [`Parse`][4], which produces an abstract syntax tree for
  the document
* Latest bug fixes
* Flexibility to easily add your own rendering extensions

Potential drawbacks:

* Our benchmarks show v2 to be slightly slower than v1. Currently in the
  ballpark of around 15%.
* API breakage. If you can't afford modifying your code to adhere to the new API
  and don't care too much about the new features, v2 is probably not for you.
* Several bug fixes are trailing behind and still need to be forward-ported to
  v2. See issue [#348](https://github.com/russross/blackfriday/issues/348) for
  tracking.

If you are still interested in the legacy `v1`, you can import it from
`github.com/russross/blackfriday`. Documentation for the legacy v1 can be found
here: https://pkg.go.dev/github.com/russross/blackfriday.


Usage
-----

For the most sensible markdown processing, it is as simple as getting your input
into a byte slice and calling:

```go
output := blackfriday.Run(input)
```

Your input will be parsed and the output rendered with a set of most popular
extensions enabled. If you want the most basic feature set, corresponding with
the bare Markdown specification, use:

```go
output := blackfriday.Run(input, blackfriday.WithNoExtensions())
```

### 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][5].

Here's an example of simple usage of Blackfriday together with Bluemonday:

```go
import (
    "github.com/microcosm-cc/bluemonday"
    "github.com/russross/blackfriday/v2"
)

// ...
unsafe := blackfriday.Run(input)
html := bluemonday.UGCPolicy().SanitizeBytes(unsafe)
```

### Custom options

If you want to customize the set of options, use `blackfriday.WithExtensions`,
`blackfriday.WithRenderer` and `blackfriday.WithRefOverride`.

### `blackfriday-tool`

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:

* <https://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.

### Sanitized anchor names

Blackfriday includes an algorithm for creating sanitized anchor names
corresponding to a given input text. This algorithm is used to create
anchors for headings when `AutoHeadingIDs` extension is enabled. The
algorithm has a specification, so that other packages can create
compatible anchor names and links to those anchors.

The specification is located at https://pkg.go.dev/github.com/russross/blackfriday/v2#hdr-Sanitized_Anchor_Names.

[`SanitizedAnchorName`](https://pkg.go.dev/github.com/russross/blackfriday/v2#SanitizedAnchorName) exposes this functionality, and can be used to
create compatible links to the anchor names generated by blackfriday.
This algorithm is also implemented in a small standalone package at
[`github.com/shurcooL/sanitized_anchor_name`](https://pkg.go.dev/github.com/shurcooL/sanitized_anchor_name). It can be useful for clients
that want a small package and don't need full functionality of blackfriday.


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 newlines in the input
    translate into line breaks in the output. This extension is off by default.

*   **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 `&ndash;`, and `---` is translated into
    `&mdash;`. 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>&frasl;<sub>5</sub>`, which renders as
    <sup>4</sup>&frasl;<sub>5</sub>.


Other renderers
---------------

Blackfriday is structured to allow alternative rendering engines. Here
are a few of note:

*   [github_flavored_markdown](https://pkg.go.dev/github.com/shurcooL/github_flavored_markdown):
    provides a GitHub Flavored Markdown renderer with fenced code block
    highlighting, clickable heading 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](https://gitlab.com/ambrevar/blackfriday-latex):
    renders output as LaTeX.

*   [bfchroma](https://github.com/Depado/bfchroma/): provides convenience
    integration with the [Chroma](https://github.com/alecthomas/chroma) code
    highlighting library. bfchroma is only compatible with v2 of Blackfriday and
    provides a drop-in renderer ready to use with Blackfriday, as well as
    options and means for further customization.

*   [Blackfriday-Confluence](https://github.com/kentaro-m/blackfriday-confluence): provides a [Confluence Wiki Markup](https://confluence.atlassian.com/doc/confluence-wiki-markup-251003035.html) renderer.

*   [Blackfriday-Slack](https://github.com/karriereat/blackfriday-slack): converts markdown to slack message style


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]: https://daringfireball.net/projects/markdown/ "Markdown"
   [2]: https://golang.org/ "Go Language"
   [3]: https://github.com/vmg/sundown "Sundown"
   [4]: https://pkg.go.dev/github.com/russross/blackfriday/v2#Parse "Parse func"
   [5]: https://github.com/microcosm-cc/bluemonday "Bluemonday"

   [BuildV2SVG]: https://travis-ci.org/russross/blackfriday.svg?branch=v2
   [BuildV2URL]: https://travis-ci.org/russross/blackfriday
   [PkgGoDevV2SVG]: https://pkg.go.dev/badge/github.com/russross/blackfriday/v2
   [PkgGoDevV2URL]: https://pkg.go.dev/github.com/russross/blackfriday/v2
Revision:	1.1
Committed:	Mon Sep 30 00:42:06 2024 UTC (6 weeks, 4 days ago) by yakumo_izuru
Branch:	MAIN
CVS Tags:	HEAD
Log Message:	Mirrored from https://git.chaotic.ninja/git/yakumo_izuru/aya
#	User	Rev	Content
1	yakumo_izuru	1.1	Blackfriday
2			[![Build Status][BuildV2SVG]][BuildV2URL]
3			[![PkgGoDev][PkgGoDevV2SVG]][PkgGoDevV2URL]
4			===========
5
6			Blackfriday is a [Markdown][1] processor implemented in [Go][2]. It
7			is paranoid about its input (so you can safely feed it user-supplied
8			data), it is fast, it supports common extensions (tables, smart
9			punctuation substitutions, etc.), and it is safe for all utf-8
10			(unicode) input.
11
12			HTML output is currently supported, along with Smartypants
13			extensions.
14
15			It started as a translation from C of [Sundown][3].
16
17
18			Installation
19			------------
20
21			Blackfriday is compatible with modern Go releases in module mode.
22			With Go installed:
23
24			go get github.com/russross/blackfriday/v2
25
26			will resolve and add the package to the current development module,
27			then build and install it. Alternatively, you can achieve the same
28			if you import it in a package:
29
30			import "github.com/russross/blackfriday/v2"
31
32			and `go get` without parameters.
33
34			Legacy GOPATH mode is unsupported.
35
36
37			Versions
38			--------
39
40			Currently maintained and recommended version of Blackfriday is `v2`. It's being
41			developed on its own branch: https://github.com/russross/blackfriday/tree/v2 and the
42			documentation is available at
43			https://pkg.go.dev/github.com/russross/blackfriday/v2.
44
45			It is `go get`-able in module mode at `github.com/russross/blackfriday/v2`.
46
47			Version 2 offers a number of improvements over v1:
48
49			* Cleaned up API
50			* A separate call to [`Parse`][4], which produces an abstract syntax tree for
51			the document
52			* Latest bug fixes
53			* Flexibility to easily add your own rendering extensions
54
55			Potential drawbacks:
56
57			* Our benchmarks show v2 to be slightly slower than v1. Currently in the
58			ballpark of around 15%.
59			* API breakage. If you can't afford modifying your code to adhere to the new API
60			and don't care too much about the new features, v2 is probably not for you.
61			* Several bug fixes are trailing behind and still need to be forward-ported to
62			v2. See issue [#348](https://github.com/russross/blackfriday/issues/348) for
63			tracking.
64
65			If you are still interested in the legacy `v1`, you can import it from
66			`github.com/russross/blackfriday`. Documentation for the legacy v1 can be found
67			here: https://pkg.go.dev/github.com/russross/blackfriday.
68
69
70			Usage
71			-----
72
73			For the most sensible markdown processing, it is as simple as getting your input
74			into a byte slice and calling:
75
76			```go
77			output := blackfriday.Run(input)
78			```
79
80			Your input will be parsed and the output rendered with a set of most popular
81			extensions enabled. If you want the most basic feature set, corresponding with
82			the bare Markdown specification, use:
83
84			```go
85			output := blackfriday.Run(input, blackfriday.WithNoExtensions())
86			```
87
88			### Sanitize untrusted content
89
90			Blackfriday itself does nothing to protect against malicious content. If you are
91			dealing with user-supplied markdown, we recommend running Blackfriday's output
92			through HTML sanitizer such as [Bluemonday][5].
93
94			Here's an example of simple usage of Blackfriday together with Bluemonday:
95
96			```go
97			import (
98			"github.com/microcosm-cc/bluemonday"
99			"github.com/russross/blackfriday/v2"
100			)
101
102			// ...
103			unsafe := blackfriday.Run(input)
104			html := bluemonday.UGCPolicy().SanitizeBytes(unsafe)
105			```
106
107			### Custom options
108
109			If you want to customize the set of options, use `blackfriday.WithExtensions`,
110			`blackfriday.WithRenderer` and `blackfriday.WithRefOverride`.
111
112			### `blackfriday-tool`
113
114			You can also check out `blackfriday-tool` for a more complete example
115			of how to use it. Download and install it using:
116
117			go get github.com/russross/blackfriday-tool
118
119			This is a simple command-line tool that allows you to process a
120			markdown file using a standalone program. You can also browse the
121			source directly on github if you are just looking for some example
122			code:
123
124			* <https://github.com/russross/blackfriday-tool>
125
126			Note that if you have not already done so, installing
127			`blackfriday-tool` will be sufficient to download and install
128			blackfriday in addition to the tool itself. The tool binary will be
129			installed in `$GOPATH/bin`. This is a statically-linked binary that
130			can be copied to wherever you need it without worrying about
131			dependencies and library versions.
132
133			### Sanitized anchor names
134
135			Blackfriday includes an algorithm for creating sanitized anchor names
136			corresponding to a given input text. This algorithm is used to create
137			anchors for headings when `AutoHeadingIDs` extension is enabled. The
138			algorithm has a specification, so that other packages can create
139			compatible anchor names and links to those anchors.
140
141			The specification is located at https://pkg.go.dev/github.com/russross/blackfriday/v2#hdr-Sanitized_Anchor_Names.
142
143			[`SanitizedAnchorName`](https://pkg.go.dev/github.com/russross/blackfriday/v2#SanitizedAnchorName) exposes this functionality, and can be used to
144			create compatible links to the anchor names generated by blackfriday.
145			This algorithm is also implemented in a small standalone package at
146			[`github.com/shurcooL/sanitized_anchor_name`](https://pkg.go.dev/github.com/shurcooL/sanitized_anchor_name). It can be useful for clients
147			that want a small package and don't need full functionality of blackfriday.
148
149
150			Features
151			--------
152
153			All features of Sundown are supported, including:
154
155			* Compatibility. The Markdown v1.0.3 test suite passes with
156			the `--tidy` option. Without `--tidy`, the differences are
157			mostly in whitespace and entity escaping, where blackfriday is
158			more consistent and cleaner.
159
160			* Common extensions, including table support, fenced code
161			blocks, autolinks, strikethroughs, non-strict emphasis, etc.
162
163			* Safety. Blackfriday is paranoid when parsing, making it safe
164			to feed untrusted user input without fear of bad things
165			happening. The test suite stress tests this and there are no
166			known inputs that make it crash. If you find one, please let me
167			know and send me the input that does it.
168
169			NOTE: "safety" in this context means runtime safety only. In order to
170			protect yourself against JavaScript injection in untrusted content, see
171			[this example](https://github.com/russross/blackfriday#sanitize-untrusted-content).
172
173			* Fast processing. It is fast enough to render on-demand in
174			most web applications without having to cache the output.
175
176			* Thread safety. You can run multiple parsers in different
177			goroutines without ill effect. There is no dependence on global
178			shared state.
179
180			* Minimal dependencies. Blackfriday only depends on standard
181			library packages in Go. The source code is pretty
182			self-contained, so it is easy to add to any project, including
183			Google App Engine projects.
184
185			* Standards compliant. Output successfully validates using the
186			W3C validation tool for HTML 4.01 and XHTML 1.0 Transitional.
187
188
189			Extensions
190			----------
191
192			In addition to the standard markdown syntax, this package
193			implements the following extensions:
194
195			* Intra-word emphasis supression. The `_` character is
196			commonly used inside words when discussing code, so having
197			markdown interpret it as an emphasis command is usually the
198			wrong thing. Blackfriday lets you treat all emphasis markers as
199			normal characters when they occur inside a word.
200
201			* Tables. Tables can be created by drawing them in the input
202			using a simple syntax:
203
204			```
205			Name \| Age
206			--------\|------
207			Bob \| 27
208			Alice \| 23
209			```
210
211			* Fenced code blocks. In addition to the normal 4-space
212			indentation to mark code blocks, you can explicitly mark them
213			and supply a language (to make syntax highlighting simple). Just
214			mark it like this:
215
216			```go
217			func getTrue() bool {
218			return true
219			}
220			```
221
222			You can use 3 or more backticks to mark the beginning of the
223			block, and the same number to mark the end of the block.
224
225			To preserve classes of fenced code blocks while using the bluemonday
226			HTML sanitizer, use the following policy:
227
228			```go
229			p := bluemonday.UGCPolicy()
230			p.AllowAttrs("class").Matching(regexp.MustCompile("^language-[a-zA-Z0-9]+$")).OnElements("code")
231			html := p.SanitizeBytes(unsafe)
232			```
233
234			* Definition lists. A simple definition list is made of a single-line
235			term followed by a colon and the definition for that term.
236
237			Cat
238			: Fluffy animal everyone likes
239
240			Internet
241			: Vector of transmission for pictures of cats
242
243			Terms must be separated from the previous definition by a blank line.
244
245			* Footnotes. A marker in the text that will become a superscript number;
246			a footnote definition that will be placed in a list of footnotes at the
247			end of the document. A footnote looks like this:
248
249			This is a footnote.[^1]
250
251			[^1]: the footnote text.
252
253			* Autolinking. Blackfriday can find URLs that have not been
254			explicitly marked as links and turn them into links.
255
256			* Strikethrough. Use two tildes (`~~`) to mark text that
257			should be crossed out.
258
259			* Hard line breaks. With this extension enabled newlines in the input
260			translate into line breaks in the output. This extension is off by default.
261
262			* Smart quotes. Smartypants-style punctuation substitution is
263			supported, turning normal double- and single-quote marks into
264			curly quotes, etc.
265
266			* LaTeX-style dash parsing is an additional option, where `--`
267			is translated into `–`, and `---` is translated into
268			`—`. This differs from most smartypants processors, which
269			turn a single hyphen into an ndash and a double hyphen into an
270			mdash.
271
272			* Smart fractions, where anything that looks like a fraction
273			is translated into suitable HTML (instead of just a few special
274			cases like most smartypant processors). For example, `4/5`
275			becomes `<sup>4</sup>&frasl;<sub>5</sub>`, which renders as
276			<sup>4</sup>&frasl;<sub>5</sub>.
277
278
279			Other renderers
280			---------------
281
282			Blackfriday is structured to allow alternative rendering engines. Here
283			are a few of note:
284
285			* [github_flavored_markdown](https://pkg.go.dev/github.com/shurcooL/github_flavored_markdown):
286			provides a GitHub Flavored Markdown renderer with fenced code block
287			highlighting, clickable heading anchor links.
288
289			It's not customizable, and its goal is to produce HTML output
290			equivalent to the [GitHub Markdown API endpoint](https://developer.github.com/v3/markdown/#render-a-markdown-document-in-raw-mode),
291			except the rendering is performed locally.
292
293			* [markdownfmt](https://github.com/shurcooL/markdownfmt): like gofmt,
294			but for markdown.
295
296			* [LaTeX output](https://gitlab.com/ambrevar/blackfriday-latex):
297			renders output as LaTeX.
298
299			* [bfchroma](https://github.com/Depado/bfchroma/): provides convenience
300			integration with the [Chroma](https://github.com/alecthomas/chroma) code
301			highlighting library. bfchroma is only compatible with v2 of Blackfriday and
302			provides a drop-in renderer ready to use with Blackfriday, as well as
303			options and means for further customization.
304
305			* [Blackfriday-Confluence](https://github.com/kentaro-m/blackfriday-confluence): provides a [Confluence Wiki Markup](https://confluence.atlassian.com/doc/confluence-wiki-markup-251003035.html) renderer.
306
307			* [Blackfriday-Slack](https://github.com/karriereat/blackfriday-slack): converts markdown to slack message style
308
309
310			TODO
311			----
312
313			* More unit testing
314			* Improve Unicode support. It does not understand all Unicode
315			rules (about what constitutes a letter, a punctuation symbol,
316			etc.), so it may fail to detect word boundaries correctly in
317			some instances. It is safe on all UTF-8 input.
318
319
320			License
321			-------
322
323			[Blackfriday is distributed under the Simplified BSD License](LICENSE.txt)
324
325
326			[1]: https://daringfireball.net/projects/markdown/ "Markdown"
327			[2]: https://golang.org/ "Go Language"
328			[3]: https://github.com/vmg/sundown "Sundown"
329			[4]: https://pkg.go.dev/github.com/russross/blackfriday/v2#Parse "Parse func"
330			[5]: https://github.com/microcosm-cc/bluemonday "Bluemonday"
331
332			[BuildV2SVG]: https://travis-ci.org/russross/blackfriday.svg?branch=v2
333			[BuildV2URL]: https://travis-ci.org/russross/blackfriday
334			[PkgGoDevV2SVG]: https://pkg.go.dev/badge/github.com/russross/blackfriday/v2
335			[PkgGoDevV2URL]: https://pkg.go.dev/github.com/russross/blackfriday/v2