XAST

0-deps configurable Abstract Syntax Tree parser

Features
Browser Support
Installing
Examples
License

Features

Configurable Lexer with predefined tokenizers
Flexible Parser with modulized AST node parsers
TypeScript support
Supports NodeJS and Browser

Support


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Installing

Using yarn:

$ yarn add xast

Using npm:

$ npm install xast

Example

Create an enum parser in file enum.ts

import {
  Parser,
  parsers,
  TokenKind,
  NodeParser,
  Node,
} from 'xast';

export interface EnumValueNode extends Node {
  readonly kind: 'ENUM_VALUE';
  readonly value: parsers.NameNode;
}

export const enumValueParser: NodeParser<EnumValueNode> = {
  kind: 'ENUM_VALUE',
  parse(parser: Parser): EnumValueNode | undefined {
    const start = parser.lexer.token;
    const value = parser.expectParse(parsers.nameParser);

    return parser.node<EnumValueNode>(start, {
      kind: 'ENUM_VALUE',
      value,
    });
  }
}

const KEYWORD = 'enum';

export interface EnumNode extends Node {
  readonly kind: 'ENUM';
  readonly name: parsers.NameNode;
  readonly values: EnumValueNode[];
}

export const enumParser: NodeParser<EnumNode> = {
  kind: 'ENUM',
  trigger: {
    kind: TokenKind.NAME,
    keyword: KEYWORD,
  },
  parse(parser: Parser): EnumNode | undefined {
    const start = parser.lexer.token;
    parser.expectKeyword(KEYWORD);
    const name = parser.expectParse(parsers.nameParser);
    parser.expectToken(TokenKind.BRACE_L);
    const values = parser.delimitedMany(TokenKind.COMMA, enumValueParser);
    parser.expectToken(TokenKind.BRACE_R);
    parser.expectToken(TokenKind.SEMICOLON);

    return parser.node<EnumNode>(start, {
      kind: 'ENUM',
      name,
      values,
    });
  }
}

Parser usage example

import {
  Lexer,
  addDefaultTokenizers,
  Parser,
  parsers
} from 'xast';

import { enumParser } from './enum.ts';

const schema = `enum Test { A, B, C };`;
const lexer = new Lexer(schema);
addDefaultTokenizers(lexer);

const parser = new Parser(lexer);
parser.add(enumParser);
console.log(parser.parseSchema());

Results to the following AST

{
  "kind": "SCHEMA",
  "definitions": [
    {
      "kind": "ENUM",
      "name": {
        "kind": "NAME",
        "value": "Test"
      },
      "values": [
        {
          "kind": "ENUM_VALUE",
          "value": {
            "kind": "NAME",
            "value": "A"
          }
        },
        {
          "kind": "ENUM_VALUE",
          "value": {
            "kind": "NAME",
            "value": "B"
          }
        },
        {
          "kind": "ENUM_VALUE",
          "value": {
            "kind": "NAME",
            "value": "C"
          }
        }
      ]
    }
  ]
}

3axap4eHko/xast

XAST

Table of Contents

Features

Support

Installing

Example

License