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# Earmark—A Pure Elixir Markdown Processor
[](https://hex.pm/packages/earmark)
[](https://hex.pm/packages/earmark)
[](https://hex.pm/packages/earmark)
## Table Of Contents
<!-- BEGIN generated TOC -->
* [Dependency](#dependency)
* [Usage](#usage)
* [Details](#details)
* [`Earmark.as_ast/2`](#earmarkas_ast2)
* [`Earmark.as_html/2`](#earmarkas_html2)
* [`Earmark.Transform.transform/2`](#earmarktransformtransform2)
* [Contributing](#contributing)
* [Author](#author)
<!-- END generated TOC -->
## Dependency
{ :earmark, "> x.y.z" }
## Usage
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### API
Earmark now exposes a well-defined and stable Abstract Syntax Tree
#### Earmark.as_ast
WARNING: This is just a proxy towards `EarmarkParser.as_ast` and is deprecated, it will be removed in version 1.5!
Replace your calls to `Earmark.as_ast` with `EarmarkParse.as_ast` as soon as possible.
**N.B.** If all you use is `Earmark.as_ast` consider _only_ using `EarmarkParser`.
The function is described below and the other two API functions `as_html` and `as_html!` are now based upon
the structure of the result of `as_ast`.
{:ok, ast, []} = EarmarkParser.as_ast(markdown)
{:ok, ast, deprecation_messages} = EarmarkParser.as_ast(markdown)
{:error, ast, error_messages} = EarmarkParser.as_ast(markdown)
#### Earmark.as_html
{:ok, html_doc, []} = Earmark.as_html(markdown)
{:ok, html_doc, deprecation_messages} = Earmark.as_html(markdown)
{:error, html_doc, error_messages} = Earmark.as_html(markdown)
#### Earmark.as_html!
html_doc = Earmark.as_html!(markdown, options)
Formats the error_messages returned by `as_html` and adds the filename to each.
Then prints them to stderr and just returns the html_doc
#### Options
Options can be passed into `as_ast/2`as well as `as_html/2` or `as_html!/2` according to the documentation.
{status, html_doc, errors} = Earmark.as_html(markdown, options)
html_doc = Earmark.as_html!(markdown, options)
{status, ast, errors} = EarmarkParser.as_ast(markdown, options)
### Command line
$ mix escript.build
$ ./earmark file.md
Some options defined in the `Earmark.Options` struct can be specified as command line switches.
Use
$ ./earmark --help
to find out more, but here is a short example
$ ./earmark --smartypants false --code-class-prefix "a- b-" file.md
will call
Earmark.as_html!( ..., %Earmark.Options{smartypants: false, code_class_prefix: "a- b-"})
## Supports
Standard [Gruber markdown][gruber].
[gruber]: <http://daringfireball.net/projects/markdown/syntax>
## Extensions
### Github Flavored Markdown
GFM is supported by default, however as GFM is a moving target and all GFM extension do not make sense in a general context, Earmark does not support all of it, here is a list of what is supported:
#### Strike Through
iex(1)> Earmark.as_html! ["~~hello~~"]
"<p>\n<del>hello</del></p>\n"
#### Syntax Highlighting
All backquoted or fenced code blocks with a language string are rendered with the given
language as a _class_ attribute of the _code_ tag.
For example:
iex(2)> [
...(2)> "```elixir",
...(2)> " @tag :hello",
...(2)> "```"
...(2)> ] |> Earmark.as_html!()
"<pre><code class=\"elixir\"> @tag :hello</code></pre>\n"
will be rendered as shown in the doctest above.
If you want to integrate with a syntax highlighter with different conventions you can add more classes by specifying prefixes that will be
put before the language string.
Prism.js for example needs a class `language-elixir`. In order to achieve that goal you can add `language-`
as a `code_class_prefix` to `Earmark.Options`.
In the following example we want more than one additional class, so we add more prefixes.
Earmark.as_html!(..., %Earmark.Options{code_class_prefix: "lang- language-"})
which is rendering
<pre><code class="elixir lang-elixir language-elixir">...
As for all other options `code_class_prefix` can be passed into the `earmark` executable as follows:
earmark --code-class-prefix "language- lang-" ...
#### Tables
Are supported as long as they are preceded by an empty line.
State | Abbrev | Capital
----: | :----: | -------
Texas | TX | Austin
Maine | ME | Augusta
Tables may have leading and trailing vertical bars on each line
| State | Abbrev | Capital |
| ----: | :----: | ------- |
| Texas | TX | Austin |
| Maine | ME | Augusta |
Tables need not have headers, in which case all column alignments
default to left.
| Texas | TX | Austin |
| Maine | ME | Augusta |
Currently we assume there are always spaces around interior vertical unless
there are exterior bars.
However in order to be more GFM compatible the `gfm_tables: true` option
can be used to interpret only interior vertical bars as a table if a seperation
line is given, therefor
Language|Rating
--------|------
Elixir | awesome
is a table (iff `gfm_tables: true`) while
Language|Rating
Elixir | awesome
never is.
#### HTML Blocks
HTML is not parsed recursively or detected in all conditons right now, though GFM compliance
is a goal.
But for now the following holds:
A HTML Block defined by a tag starting a line and the same tag starting a different line is parsed
as one HTML AST node, marked with %{verbatim: true}
E.g.
iex(3)> lines = [ "<div><span>", "some</span><text>", "</div>more text" ]
...(3)> {:ok, _, _} = EarmarkParser.as_ast(lines)
{:ok, [{"div", [], ["<span>", "some</span><text>"], %{verbatim: true}}, "more text"], []}
And a line starting with an opening tag and ending with the corresponding closing tag is parsed in similar
fashion
iex(4)> EarmarkParser.as_ast(["<span class=\"superspan\">spaniel</span>"])
{:ok, [{"span", [{"class", "superspan"}], ["spaniel"], %{verbatim: true}}], []}
What is HTML?
We differ from strict GFM by allowing **all** tags not only HTML5 tagsn this holds for oneliners....
iex(5)> {:ok, ast, []} = EarmarkParser.as_ast(["<stupid />", "<not>better</not>"])
...(5)> ast
[
{"stupid", [], [], %{verbatim: true}},
{"not", [], ["better"], %{verbatim: true}}]
and for multiline blocks
iex(6)> {:ok, ast, []} = EarmarkParser.as_ast([ "<hello>", "world", "</hello>"])
...(6)> ast
[{"hello", [], ["world"], %{verbatim: true}}]
#### HTML Comments
Are recoginized if they start a line (after ws and are parsed until the next `-->` is found
all text after the next '-->' is ignored
E.g.
iex(7)> EarmarkParser.as_ast(" <!-- Comment\ncomment line\ncomment --> text -->\nafter")
{:ok, [{:comment, [], [" Comment", "comment line", "comment "], %{comment: true}}, {"p", [], ["after"], %{}}], []}
### Adding HTML attributes with the IAL extension
#### To block elements
HTML attributes can be added to any block-level element. We use
the Kramdown syntax: add the line `{:` _attrs_ `}` following the block.
_attrs_ can be one or more of:
* `.className`
* `#id`
* name=value, name="value", or name='value'
For example:
# Warning
{: .red}
Do not turn off the engine
if you are at altitude.
{: .boxed #warning spellcheck="true"}
#### To links or images
It is possible to add IAL attributes to generated links or images in the following
format.
iex(8)> markdown = "[link](url) {: .classy}"
...(8)> Earmark.as_html(markdown)
{ :ok, "<p>\n<a class=\"classy\" href=\"url\">link</a></p>\n", []}
For both cases, malformed attributes are ignored and warnings are issued.
iex(9)> [ "Some text", "{:hello}" ] |> Enum.join("\n") |> Earmark.as_html()
{:error, "<p>\nSome text</p>\n", [{:warning, 2,"Illegal attributes [\"hello\"] ignored in IAL"}]}
It is possible to escape the IAL in both forms if necessary
iex(10)> markdown = "[link](url)\\{: .classy}"
...(10)> Earmark.as_html(markdown)
{:ok, "<p>\n<a href=\"url\">link</a>{: .classy}</p>\n", []}
This of course is not necessary in code blocks or text lines
containing an IAL-like string, as in the following example
iex(11)> markdown = "hello {:world}"
...(11)> Earmark.as_html!(markdown)
"<p>\nhello {:world}</p>\n"
## Limitations
* Block-level HTML is correctly handled only if each HTML
tag appears on its own line. So
<div>
<div>
hello
</div>
</div>
will work. However. the following won't
<div>
hello</div>
* John Gruber's tests contain an ambiguity when it comes to
lines that might be the start of a list inside paragraphs.
One test says that
This is the text
* of a paragraph
that I wrote
is a single paragraph. The "*" is not significant. However, another
test has
* A list item
* an another
and expects this to be a nested list. But, in reality, the second could just
be the continuation of a paragraph.
I've chosen always to use the second interpretation—a line that looks like
a list item will always be a list item.
* Rendering of block and inline elements.
Block or void HTML elements that are at the absolute beginning of a line end
the preceding paragraph.
Thusly
mypara
<hr />
Becomes
<p>mypara</p>
<hr />
While
mypara
<hr />
will be transformed into
<p>mypara
<hr /></p>
## Timeouts
By default, that is if the `timeout` option is not set Earmark uses parallel mapping as implemented in `Earmark.pmap/2`,
which uses `Task.await` with its default timeout of 5000ms.
In rare cases that might not be enough.
By indicating a longer `timeout` option in milliseconds Earmark will use parallel mapping as implemented in `Earmark.pmap/3`,
which will pass `timeout` to `Task.await`.
In both cases one can override the mapper function with either the `mapper` option (used if and only if `timeout` is nil) or the
`mapper_with_timeout` function (used otherwise).
For the escript only the `timeout` command line argument can be used.
## Security
Please be aware that Markdown is not a secure format. It produces
HTML from Markdown and HTML. It is your job to sanitize and or
filter the output of `Earmark.as_html` if you cannot trust the input
and are to serve the produced HTML on the Web.
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## Details
## `Earmark.as_ast/2`
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`as_ast` is a compatibility function to call `EarmarkParser.as_ast`
It is deprecated and will be removed in 1.5!
Options are passes like to `as_html`, some do not have an effect though (e.g. `smartypants`) as formatting and escaping is not done
for the AST.
iex(12)> markdown = "```elixir\nIO.puts 42\n```"
...(12)> {:ok, ast, []} = EarmarkParser.as_ast(markdown, code_class_prefix: "lang-")
...(12)> ast
[{"pre", [], [{"code", [{"class", "elixir lang-elixir"}], ["IO.puts 42"], %{}}], %{}}]
<!-- END inserted functiondoc Earmark.as_ast/2 -->
## `Earmark.as_html/2`
<!-- BEGIN inserted functiondoc Earmark.as_html/2 -->
Given a markdown document (as either a list of lines or
a string containing newlines), returns a tuple containing either
`{:ok, html_doc, error_messages}`, or `{:error, html_doc, error_messages}`
Where `html_doc` is an HTML representation of the markdown document and
`error_messages` is a list of tuples with the following elements
- `severity` e.g. `:error`, `:warning` or `:deprecation`
- line number in input where the error occurred
- description of the error
`options` can be an `%Earmark.Options{}` structure, or can be passed in as a `Keyword` argument (with legal keys for `%Earmark.Options`
* `renderer`: ModuleName
The module used to render the final document. Defaults to
`Earmark.HtmlRenderer`
* `gfm`: boolean
True by default. Turns on the supported Github Flavored Markdown extensions
* `breaks`: boolean
Only applicable if `gfm` is enabled. Makes all line breaks
significant (so every line in the input is a new line in the
output.
* `code_class_prefix`: binary
Code blocks will be rendered with prefixed class names, which might be necessary for
usage with 3rd party libraries.
Earmark.as_html("```elixir\nCode\n```", code_class_prefix: "my_prefix_")
{:ok, "<pre><code class=\"elixir my_prefix_elixir\">Code\```</code></pre>\n", []}
* `smartypants`: boolean
Turns on smartypants processing, so quotes become curly, two
or three hyphens become en and em dashes, and so on. True by
default.
So, to format the document in `original` and disable smartypants,
you'd call
alias Earmark.Options
Earmark.as_html(original, %Options{smartypants: false})
* `pure_links`: boolean
Pure links of the form `~r{\bhttps?://\S+\b}` are rendered as links from now on.
However, by setting the `pure_links` option to `false` this can be disabled and pre 1.4
behavior can be used.
* `compact_output`: boolean
If set to true, no cosmetic newlines will be emitted by Earmark. False by default.
<!-- END inserted functiondoc Earmark.as_html/2 -->
## `Earmark.Transform.transform/2`
<!-- BEGIN inserted functiondoc Earmark.Transform.transform/2 -->
Needs update for 1.4.7
<!-- END inserted functiondoc Earmark.Transform.transform/2 -->
## Contributing
Pull Requests are happily accepted.
Please be aware of one _caveat_ when correcting/improving `README.md`.
The `README.md` is generated by the mix task `readme` from `README.template` and
docstrings by means of `%moduledoc` or `%functiondoc` directives.
Please identify the origin of the generated text you want to correct and then
apply your changes there.
Then issue the mix task `readme`, this is important to have a correctly updated `README.md` after the merge of
your PR.
Thank you all who have already helped with Earmark, your names are duely noted in [CHANGELOG.md](CHANGELOG.md).
## Author
Copyright © 2014,5,6,7,8 Dave Thomas, The Pragmatic Programmers
@/+pragdave, dave@pragprog.com
# LICENSE
Same as Elixir, which is Apache License v2.0. Please refer to [LICENSE](LICENSE) for details.
SPDX-License-Identifier: Apache-2.0
