Parse a test262-format test and provide API

Usage no npm install needed!

<script type="module">
  import adrianheineTest262Parser from 'https://cdn.skypack.dev/@adrianheine/test262-parser';


Parse test262 test files

This package will allow you to parse test262 test files into their component pieces, for further use and manipulation.



The simplest function exported by this module is parseFile, which expects either a string representing the file contents, or an object with members file and contents, which are strings containing the filename and contents respectively.

The result of parseFile is an object f with (at least) a contents member.

If the input to parseFile contains the special YAML frontmatter comments /*--- ---*/, then the following things are done:

  1. the copyright message is stored in f.copyright
  2. the YAML frontmatter is parsed and stored as an object, f.attrs
  3. the test's async status (true/false) is stored in f.async
  4. f.contents is modified to contain only the text following the YAML closer comment ---*/

If the input does not contain YAML frontmatter, some of the above parsing is still attempted but the f.contents member will remain unchanged. This provides backwards compatibility to test262-runner which uses parseFile to parse test helpers as well as test files.

parseFile examples

'use strict';
var fs = require('fs');
var test262Parser = require('@adrianheine/test262-parser');

var rawTest = fs.readFileSync('built-ins/Array/prototype/includes/array-like.js');

// Pass in file object and it will be mutated with parsed data:
var file = {
    file: 'built-ins/Array/prototype/includes/array-like.js',
    contents: rawTest

// `file` now has `attrs`, `async`, and `copyright` properties, with `contents` modified

// Outputs normalized attributes from the YAML front-matter:
// https://github.com/tc39/test262/blob/master/CONTRIBUTING.md#frontmatter

// Outputs `true` or `false` depending on whether the test is async:
// https://github.com/tc39/test262/blob/master/CONTRIBUTING.md#writing-asynchronous-tests

// Outputs the copyright header:
// https://github.com/tc39/test262/blob/master/CONTRIBUTING.md#copyright

// Outputs the main test body, without the copyright or YAML front-matter.

// You can also parse test contents directly; it will create a file object
var parsedFile = test262Parser.parseFile(rawTest);

console.log(parsedFile.file);      // '<unknown>'
console.log(parsedFile.contents);  // the main test body
console.log(parsedFile.copyright); // the copyright header
console.log(parsedFile.attrs);     // the normalized attributes
consoel.log(parsedFile.async);     // whether or not the test is async


The extractYAML function takes a string containing the text contents and returns back the substring that constitutes the YAML front matter:

'use strict';
var fs = require('fs');
var test262Parser = require('@adrianheine/test262-parser');

var testContents = fs.readFileSync('built-ins/Array/prototype/includes/array-like.js');

var yaml = test262Parser.extractYAML(testContents);

will output

description: Array.prototype.includes works on array-like objects
author: Domenic Denicola

Streaming interface

The default export of the module is a transform stream factory. Every time you write a string or file object to the transform stream, it emits a parsed file object:

'use strict';
var fs = require('fs');
var test262Parser = require('@adrianheine/test262-parser');

var transformStream = test262Parser();

var testContents = fs.readFileSync('built-ins/Array/prototype/includes/array-like.js');

will output to process.stdout the (stringification of the) file object.