# Earmark—A Pure Elixir Markdown Processor
[](https://travis-ci.org/pragdave/earmark)
[](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_html/2`](#earmarkas_html2)
* [`Earmark.as_ast/2`](#earmarkas_ast2)
* [`Earmark.Transform.transform/2`](#earmarktransformtransform2)
* [Contributing](#contributing)
* [Author](#author)
<!-- END generated TOC -->
## Dependency
{ :earmark, "> x.y.z" }
## Usage
<!-- BEGIN inserted moduledoc Earmark -->
### API
#### 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)
All messages are printed to _stderr_.
#### Options:
Options can be passed into `as_html` or `as_html!` according to the [documentation](#as_html/2).
html_doc = Earmark.as_html!(markdown)
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
#### NEW and EXPERIMENTAL: `Earmark.as_ast`
Although well tested the way the exposed AST will look in future versions may change, a stable
API is expected for Earmark v1.6, when the rendered HTML shall be derived from the ast too.
More details can be found in the function's description below.
### 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><del>hello</del></p>\n"
* Syntax Highlighting
The generated code blocks have a corresponding `class` attribute:
iex(2)> Earmark.as_html! ["```elixir", " [] |> Enum.into(%{})", "```"]
"<pre><code class=\"elixir\"> [] |> Enum.into(%{})</code></pre>\n"
which can be customized with the `code_class_prefix` option
iex(3)> Earmark.as_html! ["```elixir", " [] |> Enum.into(%{})", "```"] , %Earmark.Options{code_class_prefix: "lang-"}
"<pre><code class=\"elixir lang-elixir\"> [] |> Enum.into(%{})</code></pre>\n"
* 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.
### 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(4)> markdown = "[link](url) {: .classy}"
...(4)> Earmark.as_html(markdown)
{ :ok, "<p><a href=\"url\" class=\"classy\">link</a></p>\n", []}
For both cases, malformed attributes are ignored and warnings are issued.
iex(5)> [ "Some text", "{:hello}" ] |> Enum.join("\n") |> Earmark.as_html()
{:error, "<p>Some text</p>\n", [{:warning, 2,"Illegal attributes [\"hello\"] ignored in IAL"}]}
It is possible to escape the IAL in both forms if necessary
iex(6)> markdown = "[link](url)\\{: .classy}"
...(6)> Earmark.as_html(markdown)
{:ok, "<p><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(7)> markdown = "hello {:world}"
...(7)> Earmark.as_html!(markdown)
"<p>hello {: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>
## Integration
### 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(8)> [
...(8)> "```elixir",
...(8)> " @tag :hello",
...(8)> "```"
...(8)> ] |> 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-" ...
## 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.
<!-- END inserted moduledoc Earmark -->
## Details
## `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 four 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.
<!-- END inserted functiondoc Earmark.as_html/2 -->
## `Earmark.as_ast/2`
<!-- BEGIN inserted functiondoc Earmark.as_ast/2 -->
**EXPERIMENTAL**, but well tested, just expect API changes in the 1.4 branch
iex(9)> markdown = "My `code` is **best**"
...(9)> {:ok, ast, []} = Earmark.as_ast(markdown)
...(9)> ast
[{"p", [], ["My ", {"code", [{"class", "inline"}], ["code"]}, " is ", {"strong", [], ["best"]}]}]
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(10)> markdown = "```elixir\nIO.puts 42\n```"
...(10)> {:ok, ast, []} = Earmark.as_ast(markdown, code_class_prefix: "lang-")
...(10)> ast
[{"pre", [], [{"code", [{"class", "elixir lang-elixir"}], ["IO.puts 42"]}]}]
**Rationale**:
The AST is exposed in the spirit of [Floki's](https://hex.pm/packages/floki) there might be some subtle WS
differences and we chose to **always** have tripples, even for comments.
We also do return a list for a single node
Floki.parse("<!-- comment -->")
{:comment, " comment "}
Earmark.as_ast("<!-- comment -->")
{:ok, [{:comment, [], [" comment "]}], []}
Therefore `as_ast` is of the following type
@typep tag :: String.t | :comment
@typep att :: {String.t, String.t}
@typep atts :: list(att)
@typep node :: String.t | {tag, atts, ast}
@type ast :: list(node)
<!-- END inserted functiondoc Earmark.as_ast/2 -->
## `Earmark.Transform.transform/2`
<!-- BEGIN inserted functiondoc Earmark.Transform.transform/2 -->
**EXPERIMENTAL**
But well tested, just expect API changes in the 1.4 branch
Takes an ast, and optional options (I love this pun), which can be
a map or keyword list of which the following keys will be used:
- `smartypants:` `boolean`
- `initial_indent:` `number`
- `indent:` `number`
iex(1)> transform({"p", [], [{"em", [], "help"}, "me"]})
"<p>\n <em>\n help\n </em>\n me\n</p>\n"
Right now only transformation to HTML is supported.
The transform is also agnostic to any annotation map that is added to the AST.
Only the `:meta` key is reserved and by passing annotation maps with a `:meta` key
into the AST the result might become altered or an exception might be raised, otherwise...
iex(2)> transform({"p", [], [{"em", [], ["help"], %{inner: true}}], %{level: 1}})
"<p>\n <em>\n help\n </em>\n</p>\n"
<!-- 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
