Expose the AST in the JavaScript implementation (#109)

Author: aslakhellesoy

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+- [JavaScript] Add `CucumberExpression.ast` and expose the AST types. 
+
 ## [15.0.2] - 2022-03-15
 ### Fixed
 - Add missing `name` field in CommonJS package file ([#87](https://github.com/cucumber/cucumber-expressions/pull/87))

javascript/src/Ast.ts

@@ -40,7 +40,7 @@ export interface Located {
   readonly end: number
 }
 
-export class Node {
+export class Node implements Located {
   constructor(
     public readonly type: NodeType,
     public readonly nodes: readonly Node[] | undefined,
@@ -70,7 +70,7 @@ export enum NodeType {
   expression = 'EXPRESSION_NODE',
 }
 
-export class Token {
+export class Token implements Located {
   readonly type: TokenType
   readonly text: string
   readonly start: number

javascript/src/CucumberExpression.ts

@@ -20,6 +20,7 @@ const ESCAPE_PATTERN = () => /([\\^[({$.|?*+})\]])/g
 export default class CucumberExpression implements Expression {
   private readonly parameterTypes: Array<ParameterType<unknown>> = []
   private readonly treeRegexp: TreeRegexp
+  private readonly ast: Node
 
   /**
    * @param expression
@@ -30,8 +31,8 @@ export default class CucumberExpression implements Expression {
     private readonly parameterTypeRegistry: ParameterTypeRegistry
   ) {
     const parser = new CucumberExpressionParser()
-    const ast = parser.parse(expression)
-    const pattern = this.rewriteToRegex(ast)
+    this.ast = parser.parse(expression)
+    const pattern = this.rewriteToRegex(this.ast)
     this.treeRegexp = new TreeRegexp(pattern)
   }
 
@@ -73,14 +74,14 @@ export default class CucumberExpression implements Expression {
 
   private rewriteAlternation(node: Node) {
     // Make sure the alternative parts aren't empty and don't contain parameter types
-    ;(node.nodes || []).forEach((alternative) => {
+    for (const alternative of node.nodes || []) {
       if (!alternative.nodes || alternative.nodes.length == 0) {
         throw createAlternativeMayNotBeEmpty(alternative, this.expression)
       }
       this.assertNotEmpty(alternative, (astNode) =>
         createAlternativeMayNotExclusivelyContainOptionals(astNode, this.expression)
       )
-    })
+    }
     const regex = (node.nodes || []).map((node) => this.rewriteToRegex(node)).join('|')
     return `(?:${regex})`
   }

javascript/src/index.ts

@@ -1,4 +1,5 @@
 import Argument from './Argument.js'
+import { Located, Node, NodeType, Token, TokenType } from './Ast.js'
 import CucumberExpression from './CucumberExpression.js'
 import CucumberExpressionGenerator from './CucumberExpressionGenerator.js'
 import ExpressionFactory from './ExpressionFactory.js'
@@ -17,7 +18,12 @@ export {
   ExpressionFactory,
   GeneratedExpression,
   Group,
+  Located,
+  Node,
+  NodeType,
   ParameterType,
   ParameterTypeRegistry,
   RegularExpression,
+  Token,
+  TokenType,
 }