espurify

What is espurify?

The espurify npm package is used to create a deep copy of an ESTree-compliant AST (Abstract Syntax Tree) while removing extra properties that are not part of the ESTree specification. This is useful for ensuring that ASTs are standardized and can be used in various tools and libraries that expect a clean, compliant AST.

What are espurify's main functionalities?

Deep Copy of ESTree AST

This feature allows you to create a deep copy of an ESTree-compliant AST while removing any extra properties that are not part of the ESTree specification. The code sample demonstrates parsing JavaScript code into an AST using Acorn, and then purifying that AST using espurify.

const espurify = require('espurify');
const acorn = require('acorn');

const code = 'const x = 42;';
const ast = acorn.parse(code, { ecmaVersion: 2020 });
const purifiedAst = espurify(ast);

console.log(JSON.stringify(purifiedAst, null, 2));

Other packages similar to espurify

estraverse

Estraverse is a package for traversing and manipulating ESTree-compliant ASTs. While it does not specifically purify ASTs by removing non-standard properties, it provides powerful traversal and manipulation capabilities that can be used in conjunction with espurify.

escodegen

Escodegen is a package for generating JavaScript code from an ESTree-compliant AST. It focuses on code generation rather than purification, but it can be used to regenerate code from a purified AST created by espurify.

esprima

Esprima is a high-performance, standard-compliant JavaScript parser that produces ESTree-compliant ASTs. While it does not purify ASTs, it can be used to generate the initial AST that can then be purified using espurify.

README

espurify

Clone new AST without extra properties

API

var purifiedAstClone = espurify(originalAst)

Returns new clone of originalAst but without extra properties.

Leave properties defined in Mozilla JavaScript AST spec only (Note: location informations are eliminated too).

EXAMPLE

var espurify = require('espurify'),
    estraverse = require('estraverse'),
    esprima = require('esprima'),
    syntax = estraverse.Syntax,
    assert = require('assert');

var jsCode = 'assert("foo")';

// Adding extra informations to AST
var originalAst = esprima.parse(jsCode, {tolerant: true, loc: true, raw: true});
estraverse.replace(originalAst, {
    leave: function (currentNode, parentNode) {
        if (currentNode.type === syntax.Literal && typeof currentNode.raw !== 'undefined') {
            currentNode['x-verbatim-bar'] = {
                content : currentNode.raw,
                precedence : 18  // escodegen.Precedence.Primary
            };
            return currentNode;
        } else {
            return undefined;
        }
    }
});


// purify AST
var purifiedClone = espurify(originalAst);


// original AST is not modified
assert.deepEqual(originalAst, {
  type: 'Program',
  body: [
    {
      type: 'ExpressionStatement',
      expression: {
        type: 'CallExpression',
        callee: {
          type: 'Identifier',
          name: 'assert',
          loc: {
            start: {
              line: 1,
              column: 0
            },
            end: {
              line: 1,
              column: 6
            }
          }
        },
        arguments: [
          {
            type: 'Literal',
            value: 'foo',
            raw: '"foo"',
            loc: {
              start: {
                line: 1,
                column: 7
              },
              end: {
                line: 1,
                column: 12
              }
            },
            "x-verbatim-bar": {
              content: '"foo"',
              precedence: 18
            }
          }
        ],
        loc: {
          start: {
            line: 1,
            column: 0
          },
          end: {
            line: 1,
            column: 13
          }
        }
      },
      loc: {
        start: {
          line: 1,
          column: 0
        },
        end: {
          line: 1,
          column: 13
        }
      }
    }
  ],
  loc: {
    start: {
      line: 1,
      column: 0
    },
    end: {
      line: 1,
      column: 13
    }
  },
  errors: []
});


// Extra properties are eliminated from cloned AST
assert.deepEqual(purifiedClone, {
    type: 'Program',
    body: [
        {
            type: 'ExpressionStatement',
            expression: {
                type: 'CallExpression',
                callee: {
                    type: 'Identifier',
                    name: 'assert'
                },
                arguments: [
                    {
                        type: 'Literal',
                        value: 'foo'
                    }
                ]
            }
        }
    ]
});

INSTALL

via npm

Install

$ npm install --save espurify

Use

var espurify = require('espurify');

via bower

Install

$ bower install --save espurify

Load (espurify function is exported)

<script type="text/javascript" src="./path/to/bower_components/espurify/build/espurify.js"></script>

AUTHOR

• Takuto Wada

LICENSE

Licensed under the MIT license.

Changelog

1.0.1 (2015-03-06)

• replace Array#indexOf with indexof module to deal with older browsers (4ba0bd51)
• ship browser build with npm module too (47e0cc85)

Moved repository to estools (2014-11-24)

Moved repository from twada/espurify to estools/espurify.