parcel-bundler/lib/visitors/globals.js

Blazing fast, zero configuration web application bundler

'use strict';

const Path = require('path');
const types = require('babel-types');
const matchesPattern = require('./matches-pattern');

const VARS = {
  process: asset => {
    asset.addDependency('process');
    return 'var process = require("process");';
  },
  global: () => 'var global = (1,eval)("this");',
  __dirname: asset => `var __dirname = ${JSON.stringify(Path.dirname(asset.name))};`,
  __filename: asset => `var __filename = ${JSON.stringify(asset.name)};`,
  Buffer: asset => {
    asset.addDependency('buffer');
    return 'var Buffer = require("buffer").Buffer;';
  }
};

module.exports = {
  MemberExpression(node, asset) {
    // Inline environment variables accessed on process.env
    if (matchesPattern(node.object, 'process.env')) {
      let key = types.toComputedKey(node);
      if (types.isStringLiteral(key)) {
        let val = types.valueToNode(process.env[key.value]);
        morph(node, val);
        asset.isAstDirty = true;
        asset.cacheData.env[key.value] = process.env[key.value];
      }
    }
  },

  Identifier(node, asset, ancestors) {
    let parent = ancestors[ancestors.length - 2];
    if (VARS.hasOwnProperty(node.name) && !asset.globals.has(node.name) && types.isReferenced(node, parent)) {
      asset.globals.set(node.name, VARS[node.name](asset));
    }
  },

  Declaration(node, asset, ancestors) {
    // If there is a global declaration of one of the variables, remove our declaration
    let identifiers = types.getBindingIdentifiers(node);
    for (let id in identifiers) {
      if (VARS.hasOwnProperty(id) && !inScope(ancestors)) {
        // Don't delete entirely, so we don't add it again when the declaration is referenced
        asset.globals.set(id, '');
      }
    }
  }
};

function inScope(ancestors) {
  for (let i = ancestors.length - 2; i >= 0; i--) {
    if (types.isScope(ancestors[i]) && !types.isProgram(ancestors[i])) {
      return true;
    }
  }

  return false;
}

// replace object properties
function morph(object, newProperties) {
  for (let key in object) {
    delete object[key];
  }

  for (let key in newProperties) {
    object[key] = newProperties[key];
  }
}