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Showing content from https://github.com/estools/espurify below:

estools/espurify: Clone AST without extra properties

Clone AST without extra properties

const purifiedAstClone = espurify.purifyAst(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.

(note: using espurify as a default exported function is deprecated in favor of named exports aiming ESM era, and will be removed in future major releases)

Supported ECMAScript versions

const customizedCloneFunctionWithAllowList = espurify.cloneWithAllowlist(allowList)

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

(note: espurify.cloneWithWhitelist is still exported but deprecated in favor of more inclusive language and will be removed in future major releases)

const purifiedAstClone = customizedCloneFunctionWithAllowList(originalAst)

Returns new clone of originalAst by customized function.

type default value object N/A

allowList 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'],
    ...

const customizedCloneFunction = espurify.customize(options)

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

const purifiedAstClone = customizedCloneFunction(originalAst)

Returns new clone of originalAst by customized function.

type default value object {}

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

type default value string or number 2025

Indicates the ECMAScript version to clone. Must be either 5, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025.

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.

const espurify = require('espurify');
const estraverse = require('estraverse');
const acorn = require('acorn');
const syntax = estraverse.Syntax;
const assert = require('assert');

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

// Adding extra informations to AST
const originalAst = acorn.parse(jsCode, { locations: true, ranges: true, ecmaVersion: 2022 });
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
const purifiedClone = espurify.purifyAst(originalAst);


// 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'
          }
        ],
        optional: false
      }
    }
  ],
  sourceType: 'script'
});


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

Install

$ npm install --save espurify

Use

const espurify = require('espurify');

Takuto Wada

Licensed under the MIT license.

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