$ show yuin/goldmark
Goldmark is a CommonMark-compliant Markdown parser and HTML renderer written in Go, designed for high performance and extensibility. The v2 branch introduces a complete redesign with Go generics, a cleaner separation of parser and renderer, and more semantic AST nodes. The core library exposes a `parser` package with `New()` and `Parse()` to produce an AST, and a `renderer/html` package with `New()` and `Render()` to output HTML. Extensions (tables, footnotes, strikethrough, task lists, typographer, linkify, definition lists) are implemented via a well-defined extension pattern using `parser.Extension` and `html.Extension` interfaces, making it straightforward to add custom syntax. The architecture is a library rather than a standalone application; it has no CLI or server, but is used by many static site generators and other tools. The codebase demonstrates strong engineering practices: extensive test coverage (including CommonMark spec tests and fuzzing), benchmarking against the C reference implementation, and a modular design that abstracts parsing, rendering, and text handling. The v2 version is still maturing, with some breaking changes from v1 that may affect third-party extensions, but the core is robust and well-documented.
The LLM identified 3 files worth highlighting for reuse:
Implements the delimiter stack algorithm for parsing emphasis and strong emphasis (and, by extension, strikethrough). The `DelimiterProcessor` interface and `ParseDelimiter` function encapsulate the logic for identifying delimiter runs, tracking their positions, and matching them according to the CommonMark specification. This component is isolated and could be reused in any Go project needing to parse inline markup with delimiters (e.g., custom emphasis syntax, mathematical expressions). It demonstrates non-obvious state machine design and efficient stack management.
Defines `SingleLineValue`, `MultiLineValue`, `Lines`, `Segment`, and `ValueBuilder` types that represent parsed text with source position information and pluggable decoding. The `Decoder` interface allows different text encodings (e.g., identity, HTML entity decoding, Unicode normalization) to be applied lazily. This component is fully self-contained and could be extracted into a standalone library for any project that needs to track source positions while processing text streams (e.g., compilers, linters, static analysis tools). The design elegantly separates raw source segments from decoded content.
Provides the core interfaces and helper types (`util.Prioritized`, `Option`) for building extensions that add parsers, transformers, and renderers to the goldmark pipeline. The `parser.Extension` and `html.Extension[C]` interfaces define a minimal contract that allows any extension to be composed via `WithExtensions`. This pattern is a clean example of a plugin architecture in Go, using generics to support different renderer writer types. It could be reused as a template for extensible systems that need to register prioritized components. The file is small, focused, and demonstrates how to design for composability.