SheliakLyr / syntax-diagrams

Syntax diagrams generator library for Scala

Sequence Diagrams

This library is used to generate syntax diagrams (https://en.wikipedia.org/wiki/Syntax_diagram) from Scala code. Features:

• Grammar is defined directly in Scala
• Diagrams are generated as SVG files:
  • Can be styled via CSS
  • Non-terminals can be rendered as links to separate diagrams

Usage

Diagrams are represented by type Expr. You can use its subclasses to construct primitives and combine them into larger expressions:

• Symbols
  • Terminal(value: String)
  • NonTerminal(value: String)
  • Special(value: String) - special kind of terminal. For example: textual description, regexp etc.
• Combinators
  • Repeat(e: Expr) - at least one e
  • Optional(e: Expr) - e or nothing
  • Choice(es: Seq[Expr]) - selects one of the alternatives
  • Sequence(es: Seq[Expr]) - joins es in a sequence (concatenation)

Diagrams are generated by the method SVG.createDiagram:

def createDiagram(rhs: Expr, options: Options = Options()): Tag

You can specify the following options:

• maxWidth - maximal width of the diagram. This is not a hard constraint - the generator does its best to fit the diagram but it may fail to do so.
• cssClass - css class name used in generated SVG diagram
• embeddedStyle - CSS to embed directly in SVG
• linker: String => String - method used to convert NonTerminals to HTML links. For example "#" + _. By default does nothing (_ => "").
• showNonTerm: String => String - method used to convert NonTerminals to HTML links. For example "#" + _. By default does nothing (_ => "").

Example

See JsonExampleRunner.scala for example that generates a single html page with syntax diagrams for JSON. You can see the generated page here: JSON Syntax