datasette-render-markdown

Datasette plugin for rendering Markdown.

Installation

Install this plugin in the same environment as Datasette to enable this new functionality:

datasette install datasette-render-markdown

Usage

You can explicitly list the columns you would like to treat as Markdown using plugin configuration in a metadata.json file.

Add a "datasette-render-markdown" configuration block and use a "columns" key to list the columns you would like to treat as Markdown values:

{
    "plugins": {
        "datasette-render-markdown": {
            "columns": ["body"]
        }
    }
}

This will cause any body column in any table to be treated as markdown and safely rendered using Python-Markdown. The resulting HTML is then run through Bleach to avoid the risk of XSS security problems.

Save this to metadata.json and run Datasette with the --metadata flag to load this configuration:

$ datasette serve mydata.db --metadata metadata.json

The configuration block can be used at the top level, or it can be applied just to specific databases or tables. Here's how to apply it to just the entries table in the news.db database:

{
    "databases": {
        "news": {
            "tables": {
                "entries": {
                    "plugins": {
                        "datasette-render-markdown": {
                            "columns": ["body"]
                        }
                    }
                }
            }
        }
    }
}

And here's how to apply it to every body column in every table in the news.db database:

{
    "databases": {
        "news": {
            "plugins": {
                "datasette-render-markdown": {
                    "columns": ["body"]
                }
            }
        }
    }
}

Columns that match a naming convention

This plugin can also render markdown in any columns that match a specific naming convention.

By default, columns that have a name ending in _markdown will be rendered.

You can try this out using the following query:

select '# Hello there

* This is a list
* of items

[And a link](https://github.com/simonw/datasette-render-markdown).'
as demo_markdown

You can configure a different list of wildcard patterns using the "patterns" configuration key. Here's how to render columns that end in either _markdown or _md:

{
    "plugins": {
        "datasette-render-markdown": {
            "patterns": ["*_markdown", "*_md"]
        }
    }
}

To disable wildcard column matching entirely, set "patterns": [] in your plugin metadata configuration.

Markdown extensions

The Python-Markdown library that powers this plugin supports extensions, both bundled and third-party. These can be used to enable additional Markdown features such as table support.

You can configure support for extensions using the "extensions" key in your plugin metadata configuration.

Since extensions may introduce new HTML tags, you will also need to add those tags to the list of tags that are allowed by the Bleach sanitizer. You can do that using the "extra_tags" key, and you can allow-list additional HTML attributes using "extra_attrs". See the Bleach documentation for more information on this.

Here's how to enable support for Markdown tables:

{
    "plugins": {
        "datasette-render-markdown": {
            "extensions": ["tables"],
            "extra_tags": ["table", "thead", "tr", "th", "td", "tbody"]
        }
    }
}

GitHub-Flavored Markdown

Enabling GitHub-Flavored Markdown (useful for if you are working with data imported from GitHub using github-to-sqlite) is a little more complicated.

First, you will need to install the py-gfm package:

$ pip install py-gfm

Note that py-gfm has a bug that causes it to pin to Markdown<3.0 - so if you are using it you should install it before installing datasette-render-markdown to ensure you get a compatibly version of that dependency.

Now you can configure it like this. Note that the extension name is mdx_gfm:GithubFlavoredMarkdownExtension and you need to allow-list several extra HTML tags and attributes:

{
    "plugins": {
        "datasette-render-markdown": {
            "extra_tags": [
                "hr",
                "br",
                "details",
                "summary",
                "input"
            ],
            "extra_attrs": {
                "input": [
                    "type",
                    "disabled",
                    "checked"
                ],
            },
            "extensions": [
                "mdx_gfm:GithubFlavoredMarkdownExtension"
            ]
        }
    }
}

The <input type="" checked disabled> attributes are needed to support rendering checkboxes in issue descriptions.

Markdown in templates

The plugin introduces a new template tag: {% markdown %}...{% endmarkdown %} - which can be used to render Markdown in your Jinja templates.

{% markdown %}
# This will be rendered as markdown
{% endmarkdown %}

You can use attributes on the {% markdown %} tag to enable extensions and allow-list additional tags and attributes:

{% markdown
  extensions="tables"
  extra_tags="table thead tr th td tbody" 
  extra_attrs="p:id,class a:name,href" %}
## Markdown table

First Header  | Second Header
------------- | -------------
Content Cell  | Content Cell
Content Cell  | Content Cell

<a href="https://www.example.com/" name="namehere">Example</a>
<p id="paragraph" class="klass">Paragraph</p>
{% endmarkdown %}

The extensions= and extra_tags= attributes accept a space-separated list of values.

The extra_attrs= attribute accepts a space-separated list of tag:attr1,attr2 values - each tag can specify one or more attributes that should be allowed.

You can also use the {{ render_markdown(...) }} function, like this:

{{ render_markdown("""
## Markdown table

First Header  | Second Header
------------- | -------------
Content Cell  | Content Cell
Content Cell  | Content Cell
""", extensions=["tables"],
    extra_tags=["table", "thead", "tr", "th", "td", "tbody"])) }}

The {% markdown %} tag is recommended, as it avoids the need to \" escape quotes in your Markdown content.

datasette-render-markdown by simonw