prepack/lib/evaluators/LogicalExpression.js

Execute a JS bundle, serialize global state and side effects to a snapshot that can be quickly restored.

"use strict";

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

exports.default = function (ast, strictCode, env, realm) {
  let lref = env.evaluate(ast.left, strictCode);
  let lval = _singletons.Environment.GetValue(realm, lref);

  if (lval instanceof _index.ConcreteValue) {
    let lbool = _singletons.To.ToBoolean(realm, lval);

    if (ast.operator === "&&") {
      // ECMA262 12.13.3
      if (lbool === false) return lval;
    } else {
      (0, _invariant2.default)(ast.operator === "||");
      // ECMA262 12.13.3
      if (lbool === true) return lval;
    }

    let rref = env.evaluate(ast.right, strictCode);
    return _singletons.Environment.GetValue(realm, rref);
  }
  (0, _invariant2.default)(lval instanceof _index.AbstractValue);
  let lcond = _singletons.Environment.GetConditionValue(realm, lref);

  if (!lcond.mightNotBeFalse()) return ast.operator === "||" ? env.evaluate(ast.right, strictCode) : lval;
  if (!lcond.mightNotBeTrue()) return ast.operator === "&&" ? env.evaluate(ast.right, strictCode) : lval;

  // Create empty effects for the case where ast.right is not evaluated
  let [compl1, gen1, bindings1, properties1, createdObj1] = (0, _realm.construct_empty_effects)(realm);
  compl1; // ignore

  // Evaluate ast.right in a sandbox to get its effects
  let wrapper = ast.operator === "&&" ? _singletons.Path.withCondition : _singletons.Path.withInverseCondition;
  let [compl2, gen2, bindings2, properties2, createdObj2] = wrapper(lval, () => realm.evaluateNodeForEffects(ast.right, strictCode, env));

  // Join the effects, creating an abstract view of what happened, regardless
  // of the actual value of lval.
  // Note that converting a value to boolean never has a side effect, so we can
  // use lval as is for the join condition.
  let joinedEffects;
  if (ast.operator === "&&") {
    joinedEffects = _singletons.Join.joinEffects(realm, lval, [compl2, gen2, bindings2, properties2, createdObj2], [lval, gen1, bindings1, properties1, createdObj1]);
  } else {
    joinedEffects = _singletons.Join.joinEffects(realm, lval, [lval, gen1, bindings1, properties1, createdObj1], [compl2, gen2, bindings2, properties2, createdObj2]);
  }
  let completion = joinedEffects[0];
  if (completion instanceof _completions.PossiblyNormalCompletion) {
    // in this case the evaluation of ast.right may complete abruptly, which means that
    // not all control flow branches join into one flow at this point.
    // Consequently we have to continue tracking changes until the point where
    // all the branches come together into one.
    completion = realm.composeWithSavedCompletion(completion);
  }
  // Note that the effects of (non joining) abrupt branches are not included
  // in joinedEffects, but are tracked separately inside completion.
  realm.applyEffects(joinedEffects);

  // return or throw completion
  if (completion instanceof _completions.AbruptCompletion) throw completion;
  (0, _invariant2.default)(completion instanceof _index.Value); // references do not survive join
  if (lval instanceof _index.Value && compl2 instanceof _index.Value) {
    // joinEffects does the right thing for the side effects of the second expression but for the result the join
    // produces a conditional expressions of the form (a ? b : a) for a && b and (a ? a : b) for a || b
    // Rather than look for this pattern everywhere, we override this behavior and replace the completion with
    // the actual logical operator. This helps with simplification and reasoning when dealing with path conditions.
    completion = _index.AbstractValue.createFromLogicalOp(realm, ast.operator, lval, compl2, ast.loc);
  }
  return completion;
};

var _completions = require("../completions.js");

var _realm = require("../realm.js");

var _index = require("../values/index.js");

var _environment = require("../environment.js");

var _singletons = require("../singletons.js");

var _invariant = require("../invariant.js");

var _invariant2 = _interopRequireDefault(_invariant);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
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