Mermaid Parser

Mermaid parser package

How the package works

The package exports a parse function that has two parameters:

1declare function parse<T extends DiagramAST>(
2  diagramType: keyof typeof initializers,
3  text: string
4): T;

How does a Langium-based parser work?

1sequenceDiagram
2actor Package
3participant Module
4participant TokenBuilder
5participant Lexer
6participant Parser
7participant ValueConverter
8
9
10Package ->> Module: Create services
11Module ->> TokenBuilder: Override or/and<br>reorder rules
12TokenBuilder ->> Lexer: Read the string and transform<br>it into a token stream
13Lexer ->> Parser: Parse token<br>stream into AST
14Parser ->> ValueConverter: Clean/modify tokenized<br>rules returned value
15ValueConverter -->> Package: Return AST

• When to override TokenBuilder?

  • To override keyword rules.
  • To override terminal rules that need a custom function.
  • To manually reorder the list of rules.

• When to override Lexer?

  • To modify input before tokenizing.
  • To insert/modify tokens that cannot or have not been parsed.

• When to override LangiumParser?

  • To insert or modify attributes that can't be parsed.

• When to override ValueConverter?

  • To modify the returned value from the parser.