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8.0 Migration Notes


In general, there are a couple things to be aware of when upgrading to 8.0.

  • Some previously deprecated features are now removed: tabbed code blocks via SuperFences and ExtraRawHTML. These were originally deprecated as they are now redundant, and information is provided to allow you to get the same behavior as before.

  • One of the most invasive changes was adding the support of defining arbitrary attributes on code blocks in SuperFences via the brace header format. This caused numerous changes that affects those who define their own custom fences. If you are only using the builtin fences provided by SuperFences, you will likely notice no adverse affects, but will be able to take advantage of new the new features being offered.

Better Support for JS Highlighters

  • SuperFences adds the ability, when using the brace header format (```{.lang .class #id attr=value}) to add arbitrary HTML attributes to code blocks. By default, all classes, IDs and and attributes are added to the code block of the generated output. The one exception is that the default highlight class is always added to the top level element.

    For instance, if a user needed to specify that a line number starts with an attribute data-linenum-start, they could simply use the brace header format to define this new attribute:

    ```{.python data-linenum-start="30"}
    import sys

    Attributes will only be used when Python Markdown's attr_list extension is enabled. Attributes will also be ignored when using Pygments as Pygments doesn't directly support adding IDs or arbitrary attributes.

    This allows for more extensive configuration when using JavaScript highlighters. Now users can set the appropriate attributes to configure line numbers and other highlighter specific features without the Highlight extension getting in the way.

  • Some JS highlighters may require attributes and classes to be assigned to the pre element, so the Highlight extension has added a new feature called code_attr_on_pre. This new option will ensure that custom classes, IDs, and attributes are applied to the pre element instead.

  • By default, JavaScript ready code blocks would normally have the specified language class prefixed with language-. This follows the HTML 5 specification, but some highlighters may prefer something different. The prefix can now be changed with the new Highlight option called language_prefix.

Retired Features

  • The legacy tab feature has been removed from SuperFences. This does not mean tab support is dead as the Tabbed extension actually provides an even more useful, general purpose, solution. It was impossible to keep this legacy feature around, in its current implementation, after the restructure of for attribute list support, so we decided to officially retire this already deprecated feature.

  • ExtraRawHTML has officially been removed. This extension only existed because Python Markdown did not have the feature exposed in a manner that allowed you to use it without including all of their "Extra" extension, now that Python Markdown has exposed this extension by itself, there is no longer a reason for us expose it via ExtraRawHTML. Please use Python Markdown's md_in_html extension instead to get the same exact functionality.

Custom Fence Changes

SuperFences made numerous changes so that users who wish not to use Pygments can set arbitrary attributes via the brace header format so that can more extensively configure their code blocks for JavaScript syntax highlighters. This required changes to how custom fences were handled.

  • Custom fence formatters are now expected to take a new keyword attribute called attrs. attrs contains a dictionary of key/value pairs defining attributes that should be attached to the main block element generated by a given formatter. In general, custom formatters should handle these, but are not required to. At the very least, they should be updated to take the argument even if they don't do anything with them. Custom fences that do not accept this parameter will silently fail. If your custom fence already accepts **kwargs (as recommended in the 7.0 release), your fence should continue to work even you do not do anything with the attributes. No use and apply the new, attributes, you will have to read the attrs parameter and set those to one of the elements in your generated HTML.

  • Custom fence validators have been updated to handle validation of inputs by assigning valid inputs to either an options dictionary or an attrs dictionary. The new function signature looks like this: validator(language, inputs, options, attrs, md):.

    • inputs contains all the parsed key/value pairs and should never be modified. options should have inputs added to it that configure a formatter's features. You should parse, format and assign all inputs that are considered options to the option dictionary.

    • attrs normally would contain copies of any non-option key/value pairs from inputs, unaltered. These would usually be applied to HTML elements as attributes.

    • md is the Markdown class instance and is useful if you want to access meta data or anything else in your validator.

      SuperFences will detect if you are using an older validator and should gracefully transition and use the old format, but it is strongly recommended to use the new format. If you run into any issues, you are required to update to the new format. In a future version, the graceful transition will be removed.

  • Since attributes and options are now parsed via the attr_list extension, custom fences can no longer allow inputs in the form key= (with no value), they must be in the form key, key="value" or key=value. When defining an input in the form key (with no value), the value will be the key name (this is how attr_list handles such cases). To specify an empty key, please use key="".

  • If a custom validator fails, SuperFences will now gracefully handle the error and try the next custom fence in the queue. If a custom formatter fails. If you suspect your custom validator is not working, you should add your own debug code to your custom fence to verify whether it is failing or not.

  • SuperFences will gracefully handle the error and abort processing the fence. If you suspect your custom formatter is not working, you should add your own debug code to your custom fence to verify whether it is failing or not.

New Extension

SaneHeaders implements Markdown headers more like CommonMark. Headers require a space after the # symbol in order for the line to be treated as a header. This allows you to use MagicLink issues at the start of a line. See SaneHeaders documentation for more information.