An Asciidoc extension for converting syntax grammars into RailRoad diagrams.

The extension reads a block containing an EBNF grammar, and converts the block into a railroad diagram.

= Test file

[grammkit]
----
start = left ("+" / "-") right
number = digits
digits = "1" / "2" / "3"
left = "("
right = ")"
----

Behind the scenes, asciidoctor-grammkit uses the most excellent Grammkit to do all the grunt work, which means the extension can parse ebnf, pegjs, and ohm formats to produce the diagrams.

The extension will produce a set of clickable references along with each diagram in the syntax tree; if you'd prefer to have the diagrams without references (though I'm not sure why you would) then add a references option to the grammkit tag.

= Test file

[grammkit, references="false"]
----
start = left ("+" / "-") right
number = digits
digits = "1" / "2" / "3"
left = "("
right = ")"
----

You can also supply a format parameter to tag:

= Test file

[grammkit, format="ebnf"]
----
Query	  ::=  	Prologue
                    ( SelectQuery | ConstructQuery | DescribeQuery | AskQuery )
Prologue	  ::=  	BaseDecl? PrefixDecl*
BaseDecl	  ::=  	'BASE' IRI_REF
PrefixDecl	  ::=  	'PREFIX' PNAME_NS IRI_REF
SelectQuery	  ::=  	'SELECT' ( 'DISTINCT' | 'REDUCED' )? ( Var+ | '*' ) DatasetClause* WhereClause SolutionModifier
ConstructQuery	  ::=  	'CONSTRUCT' ConstructTemplate DatasetClause* WhereClause SolutionModifier
DescribeQuery	  ::=  	'DESCRIBE' ( VarOrIRIref+ | '*' ) DatasetClause* WhereClause? SolutionModifier
AskQuery	  ::=  	'ASK' DatasetClause* WhereClause
DatasetClause	  ::=  	'FROM' ( DefaultGraphClause | NamedGraphClause )
DefaultGraphClause	  ::=  	SourceSelector
NamedGraphClause	  ::=  	'NAMED' SourceSelector
SourceSelector	  ::=  	IRIref
WhereClause	  ::=  	'WHERE'? GroupGraphPattern
SolutionModifier	  ::=  	OrderClause? LimitOffsetClauses?
LimitOffsetClauses	  ::=  	( LimitClause OffsetClause? | OffsetClause LimitClause? )
OrderClause	  ::=  	'ORDER' 'BY' OrderCondition+
OrderCondition	  ::=  	( ( 'ASC' | 'DESC' ) BrackettedExpression )
                                | ( Constraint | Var )
LimitClause	  ::=  	'LIMIT' INTEGER
OffsetClause	  ::=  	'OFFSET' INTEGER
----

Grammkit is pretty good at working out what sort of syntax language you're using (ebnf, pegjs, or ohm), but if you have a syntax error in your spec, then adding a format will give you error messages which you may find a bit more useful.

The extension is set up on npmjs, so you can just install it with the following command line:

npm install asciidoctor-grammkit

The extension works with the Antora technical documentation framework.

1. Install the extension in Antora's home directory. (This should a valid node installation).

   npm install asciidoctor-grammkit

2. Add the extension to the extensions section of to the Antora playbook

  extensions:
    - ./lib/source-url-include-processor.js
    - ./lib/json-config-ui-block-macro.js
    - ./lib/inline-man-macro.js
    - ./lib/multirow-table-head-tree-processor.js
    - ./lib/swagger-ui-block-macro.js
    - ./lib/markdown-block.js
    - asciidoctor-kroki
    - asciidoctor-external-callout
    - asciidoctor-grammkit

The extension will generate the diagrams in SVG format, but without a stylesheet, they'r not going to much more than dark patches all over the web page. There's a stylesheet in the node package called railroad.css. You should put that wherever the HTML pages are being generated, or add them to your own stylesheet. Alternatively, just copy them from below:

svg.railroad-diagram {
  background-color: rgb(255,255 ,255);
}
svg.railroad-diagram path {
  stroke-width: 3;
  stroke: black;
  fill: none;
}
svg.railroad-diagram text {
  font: bold 14px monospace;
  text-anchor: middle;
  cursor: pointer;
}
svg.railroad-diagram text.label {
  text-anchor: start;
}
svg.railroad-diagram text.comment {
  font: italic 12px monospace;
}
svg.railroad-diagram rect {
  stroke-width: 3;
  stroke: black;
  fill: hsl(120,100%,90%);
}

The extension can run standalone by adding it to Asciidoctor's extension registry.

let {generate_diagram, generate_diagram_from_text} = require('../asciidoctor-grammkit')
const asciidoctor = require('@asciidoctor/core')()
const registry = asciidoctor.Extensions.create()
require('../asciidoctor-grammkit')(registry)


test('Basic Test 1', () => {

    let input_document = ` 
[railroad]
----
start = left ("+" / "-") right
number = digits
----
`

    let converted_doc = asciidoctor.convert(input_document,{safe: 'safe', standalone: true,
        extension_registry: registry})

})