babel-plugin-shield/dist/index.js

A babel plugin to shield code against undefined properties

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _slicedToArray = function () { function sliceIterator(arr, i) { var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"]) _i["return"](); } finally { if (_d) throw _e; } } return _arr; } return function (arr, i) { if (Array.isArray(arr)) { return arr; } else if (Symbol.iterator in Object(arr)) { return sliceIterator(arr, i); } else { throw new TypeError("Invalid attempt to destructure non-iterable instance"); } }; }();

exports.default = function (_ref) {
  var t = _ref.types;

  return {
    visitor: {
      CallExpression: function CallExpression(path) {
        var node = path.node;
        if (t.isIdentifier(node.callee, { name: 'shield_' })) {
          var finalexpr = transform(path, node, t);
          path.replaceWith(finalexpr);
        }
      }
    }
  };
};

function replaceObject(t, expression, variable) {
  switch (expression.type) {
    case 'MemberExpression':
      expression.object = variable;
      break;
    case 'CallExpression':
      expression.callee = variable;
      break;
  }
  return expression;
}

function transformHelper(path, expression, t) {
  var leftExpr,
      rightExpr = expression,
      finalExpr = expression,
      refs = [],
      temp = [],
      newVar;
  if (expression) {
    switch (expression.type) {
      case 'MemberExpression':
        var _transformHelper = transformHelper(path, expression.object, t);

        var _transformHelper2 = _slicedToArray(_transformHelper, 2);

        leftExpr = _transformHelper2[0];
        temp = _transformHelper2[1];

        break;
      case 'CallExpression':
        var _transformHelper3 = transformHelper(path, expression.callee, t);

        var _transformHelper4 = _slicedToArray(_transformHelper3, 2);

        leftExpr = _transformHelper4[0];
        temp = _transformHelper4[1];

        break;
    }
    if (leftExpr) {
      newVar = path.scope.generateUidIdentifier("uid");
      refs = temp.concat(t.variableDeclarator(newVar, leftExpr));
      finalExpr = t.logicalExpression('&&', newVar, replaceObject(t, rightExpr, newVar));
    }
  }
  return [finalExpr, refs];
}

function transform(path, expression, t) {
  var _transformHelper5 = transformHelper(path, expression.arguments[0], t, null),
      _transformHelper6 = _slicedToArray(_transformHelper5, 2),
      logicalExpr = _transformHelper6[0],
      refs = _transformHelper6[1];

  var blockArgs = [t.returnStatement(logicalExpr)];
  if (refs.length > 0) {
    blockArgs = [t.variableDeclaration('var', refs), t.returnStatement(logicalExpr)];
  }

  var newBlock = t.blockStatement(blockArgs);
  return t.expressionStatement(t.callExpression(t.callExpression(t.memberExpression(t.functionExpression(null, [], newBlock, false, false), t.identifier('bind')), [t.thisExpression()]), []));
}