myst-transforms

myst-transforms

unifiedjs transforms for working with MyST Markdown documents.

Overview

These transforms take MDAST from mystjs and turn it into usable forms, enforce document structure, or provide other utilities.

These utilities are available on npm:

npm install myst-transforms

You can use the plugins as follows:

import { unified } from 'unified';
import { mathPlugin } from 'myst-transforms';

unified()
  .use(mathPlugin, { macros: {} }) // Add the plugin with any options
  .run(tree); // Run the mdast through the set of plugins

// The mdast tree has now been modified in place.

List of Transforms

Admonitions : Add headers to each admonition (callout), such as Note or Important. : Optionally replace the header with the first paragraph of text if it is all bold.

Blocks : Ensure that all blocks in a document are not nested.

Caption : Ensure that figure captions are in paragraphs

Code : Audit code to ensure that languages are specified, or provide a default language : Ensure that python as a language is replaced from IPython3 or other kernal-like language specifiers.

CodeBlock : Codeblocks can live inside of figures, have captions and be references. Transformation ensures that this information isn't lost from the original parsing of mdast. : Note: this should move into the parser in the future.

Footnotes : Pull the footnote definitions into a reference object.

HTML : Parse HTML nodes and replace their contents.

HTML Ids : Ensure that referenceable nodes have proper HTML Ids (start with a letter, no spaces or fancy characters) : HTML Ids are more strict than the internal labels used for cross-references, and this is up to the transform to provide, not the renderer.

Images : Add alt text to images if it is not defined, from the captions.

Keys : Add unique identifiers to each node, helpful for rendering as well as referring to a document in the wild. These are not aiming to be persisted across multiple builds of the document, for that you should use a label (and associated HTML Id).

Math : Use KaTeX to create and provide errors/warnings about math rendering.

Math Label : Parse latex to strip \label and simple equation environments from math, and put this in mdast directly.

MyST Cleanup : A few utilities for lifting children and getting rid of some information about the parsed document from MyST. For example, the mystDirective and mystRole wrapper nodes are removed.

Targets : Propagate targets (i.e. (my-id)=) to the following node : Add HTML friendly identifiers to headings.

Plugin Collections

A few of the plugins are exposed in a basicTransformationsPlugin does a number of the expected transformations without any user supplied options. See the code for exactly which plugins are included. If you are depending on this, ideally use the individual plugins directly, which will always provide options.

Enumeration

There are two stages to add information about numbering and cross-referencing of content, specifically, enumerateTargetsPlugin and resolveReferencesPlugin these can be run at different times depending on if you are in a single-document or multi-document setup.

The enumeration transforms require state, and can instantiate a ReferenceState object or a MultiPageReferenceState for collections with multiple pages. The reference resolution is defined in those classes. To create your own reference management, use the IReferenceState interface to pass in.

The enumerateTargetsPlugin should be run early, and registers targets with the state through state.addTarget. This will also tick forward all of the counting in the document (e.g. "Section 3.2.4" or "Figure 5"). The numbering can be configured with a numbering option in the ReferenceState, or your own implementation of counting.

The resolveReferencesPlugin has a number of transformations for (1) links, which identify document level links to other md files; (2) crossReference transforms which link references in the state and replace children with, for example, "Figure 1"; and (3) inserting caption numbers into containers.

Naming Conventions

There are two many types of exports transforms and plugins the plugins are unifiedjs plugins that can be chained together, for example, unified().use(myPlugin, opts).use(myOtherPlugin). These plugins are generally very light wrappers around transforms which are the funcitonal analogues of the plugin. The transforms are called on a tree, for example, myTransform(tree, opts).

In all cases transformations are completed in place on the mdast tree.

Error Reporting

The package uses vfile error reporting messages, this allows you to collect

import { VFile } from 'vfile';

const file = new VFile();

unified()
  .use(mathPlugin, { macros: {} }) // Add the plugin with any options
  .run(tree, file); // Run the mdast through the set of plugins

// Check for errors in the messages:
file.messages;

You can also use vfile-reporter to pretty print the messages for the console.

import { fileWarn } from 'myst-utils';

fileWarn(file, 'Replacing \\begin{eqnarray} with \\begin{align*}', {
  node,
  note: 'Although the standard eqnarray environment is available in LaTeX, ...',
  source: 'myst-transforms:math', // colon separated
  url: 'http://anorien.csc.warwick.ac.uk/mirrors/CTAN/macros/latex/required/amsmath/amsldoc.pdf',
});