Recode

Recode is a tiny unified interface for translating javascript into UNIST compliant jsAST format, performing transformations, and converting them back again!

Production

This library is not production ready. Look forward to when the npm version no longer is tagged -experimental

Introduction

Out of the box, recode transpiles javascript: javascript code is given, reformatted, and rewritten. Pass in some scripts, out come some scripts. Usually small programmatically irrelevant details are stripped (such as idiosyncratic spacing habits, or strange parenthesis placement). However, a lot more can be done by passing in plugins.

Vision

Recode will bridge the three largest tree transforming javascript plugin ecosystems: Babel, Acorn, and Unified.

Installation

NPM:

npm install node-recode

Usage

var recode = require('recode');
var fs = require('fs')
var exampleJS = fs.readFileSync('./example.js', 'utf8')
var map = require('unist-util-map');
var select = require('unist-util-select');

recode()
  .use(function example () {
    return function transformer (ast) {
      var target;
      select(ast, 'VariableDeclarator').forEach(function retrieveVariableName (node) {
        if (node.type.match(/VariableDeclarator/)) {

            //Grab where require is called, and where it requires 'recode'
            if (select(node, 'Callee Identifier[name=require]').length > 0 && 
                select(node, 'CallExpression Literal[value*=recode]').length > 0) {

              //Retrieve the variable identifier set here.
              var varNameNode = select(node, 'VariableIdentification Identifier')

              //Save it for mischevious.
              target = varNameNode[0].name
            }
        }
      })
      
      return map(ast, function (node) {
        if (node.type.match('Identifier') && node.name === target) {

          //Rename the recode variable everywhere it is mentioned in this program
          node.name = "TheGreatestLibraryEver"

        }
        return node
      });
    }
  })
  .process(exampleJS, function (err, file) {
    console.log(file.contents);
  });

Yields:

var TheGreatestLibraryEver = require('recode');
var fs = require('fs');
var exampleJS = fs.readFileSync('./example.js', 'utf8');
var map = require('unist-util-map');
var select = require('unist-util-select');
TheGreatestLibraryEver().use(function example() {
    return function transformer(ast) {
        var target;
        select(ast, 'VariableDeclarator').forEach(function retrieveVariableName(node) {
            if (node.type.match(/VariableDeclarator/)) {
                //Grab where require is called, and where it requires 'recode'
                if (select(node, 'Callee Identifier[name=require]').length > 0 && select(node, 'CallExpression Literal[value*=recode]').length > 0) {
                    //Retrieve the variable identifier set here.
                    var varNameNode = select(node, 'VariableIdentification Identifier');    //Save it for mischevious.
                    //Save it for mischevious.
                    target = varNameNode[0].name;
                }
            }
        });
        return map(ast, function (node) {
            if (node.type.match('Identifier') && node.name === target) {
                //Rename the recode variable everywhere it is mentioned in this program
                node.name = 'TheGreatestLibraryEver';
            }
            return node;
        });
    };
}).process(exampleJS, function (err, file) {
    console.log(file.contents);
});

Acknowledgments

This library has only been made possible by the work of Titus Wormer. Everything about Recode has been modeled after his Rehype, Remark, and Retext libraries, even the name! The tests couldn't be possible if not for the espree repository itself.

Todo

• [ ] Extend tests to verify support for ES2015, ES6, ES7
• [ ] Spread Operator
• [ ] Usage Documentation (hint: it assumes you are using a vfile)
• [ ] jsAST Specification
• [ ] BabylonAST<>jsAST