espurify

Clone AST without extra properties

API

var purifiedAstClone = espurify(originalAst)

Returns new clone of originalAst but without extra properties.

Leaves properties defined in The ESTree Spec (formerly known as Mozilla SpiderMonkey Parser API) only. Also note that extra informations (such as loc, range and raw) are eliminated too.

Supported ECMAScript versions

• ES5
• ES2015
• ES2016
• ES2017
• ES2018
• ES2019

var customizedCloneFunctionWithWhiteList = espurify.cloneWithWhitelist(whiteList)

Returns customized function for cloning AST, with user-provided whiteList.

var purifiedAstClone = customizedCloneFunctionWithWhiteList(originalAst)

Returns new clone of originalAst by customized function.

whiteList

type	default value
object	N/A

whiteList is an object containing NodeType as keys and properties as values.

{
    ArrayExpression: ['type', 'elements'],
    ArrayPattern: ['type', 'elements'],
    ArrowFunctionExpression: ['type', 'id', 'params', 'body', 'generator', 'expression'],
    AssignmentExpression: ['type', 'operator', 'left', 'right'],
    ...

var customizedCloneFunction = espurify.customize(options)

Returns customized function for cloning AST, configured by custom options.

var purifiedAstClone = customizedCloneFunction(originalAst)

Returns new clone of originalAst by customized function.

options

type	default value
object	{}

Configuration options. If not passed, default options will be used.

options.extra

type	default value
array of string	null

List of extra properties to be left in result AST. For example, functions returned by espurify.customize({extra: ['raw']}) will preserve raw properties of Literal. Functions return by espurify.customize({extra: ['loc', 'range']}) will preserve loc and range properties of each Node.

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');

AUTHOR

• Takuto Wada

CONTRIBUTORS

• Renée Kooi
• Andreas Lind

LICENSE

Licensed under the MIT license.