pegmd

Parses a Markdown document that follows CommonMark v0.30 to an abstract syntax tree by defining its parsing expression grammar (PEG) with pest. The crate also optionally provides a transformer to emit the AST as HTML if the html feature included.

Usage

Creating an AST

The main function exported from the crate, ast::parse_document, accepts a &str and on success returns a Node with the same lifetime as the input.

Traversal

From there, you can traverse the tree by creating a struct that implements the traversal::Vistor trait and providing it to the Node::traverse method.

HTML Conversion

If the html feature is enabled, the crate provides the html::HTMLTransformer struct that implements the Visitor trait to create a well-formatted HTML output.

Unsupported

• Document streaming. Because pest lacks support for streaming, this crate also can't read a document from a stream.

Current Limitations

While the end goal for the parser is to support the entire CommonMark spec, it currently doesn't support:

• Thematic breaks (aka horizontal rules)
• Reference links
• HTML blocks
• Setext headings
• ATX headings with closing hashes
• Entity references
• Using a tilde (~) to fence a codeblock
• Fenced codeblocks without a closing fence run until the end of the document rather than to the end of the container block
• Some of the edge cases for block quotes aren't handled per the spec. Specifically examples 247 through 252

All of these are a WIP and will be added to the parser.