babel/lib/6to5/transformation/transformers/generators/runtime.js

/**
* Copyright (c) 2014, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* https://raw.github.com/facebook/regenerator/master/LICENSE file. An
* additional grant of patent rights can be found in the PATENTS file in
* the same directory.
*/

var iteratorSymbol = typeof Symbol === "function" && Symbol.iterator || "@@iterator";
var runtime = global.regeneratorRuntime = exports;
var hasOwn = Object.prototype.hasOwnProperty;

var wrap = runtime.wrap = function wrap(innerFn, outerFn, self, tryList) {
  return new Generator(innerFn, outerFn, self || null, tryList || []);
};

var GenStateSuspendedStart = "suspendedStart";
var GenStateSuspendedYield = "suspendedYield";
var GenStateExecuting = "executing";
var GenStateCompleted = "completed";

// Returning this object from the innerFn has the same effect as
// breaking out of the dispatch switch statement.
var ContinueSentinel = {};

// Dummy constructor that we use as the .constructor property for
// functions that return Generator objects.
var GF = function GeneratorFunction() {};
var GFp = function GeneratorFunctionPrototype() {};
var Gp = GFp.prototype = Generator.prototype;
(GFp.constructor = GF).prototype =
  Gp.constructor = GFp;

// Ensure isGeneratorFunction works when Function#name not supported.
var GFName = "GeneratorFunction";
if (GF.name !== GFName) GF.name = GFName;
if (GF.name !== GFName) throw new Error(GFName + " renamed?");

runtime.isGeneratorFunction = function (genFun) {
  var ctor = genFun && genFun.constructor;
  return ctor ? GF.name === ctor.name : false;
};

runtime.mark = function (genFun) {
  genFun.__proto__ = GFp;
  genFun.prototype = Object.create(Gp);
  return genFun;
};

runtime.async = function (innerFn, outerFn, self, tryList) {
  return new Promise(function (resolve, reject) {
    var generator = wrap(innerFn, outerFn, self, tryList);
    var callNext = step.bind(generator.next);
    var callThrow = step.bind(generator["throw"]);

    function step(arg) {
      var info;
      var value;

      try {
        info = this(arg);
        value = info.value;
      } catch (error) {
        return reject(error);
      }

      if (info.done) {
        resolve(value);
      } else {
        Promise.resolve(value).then(callNext, callThrow);
      }
    }

    callNext();
  });
};

function Generator(innerFn, outerFn, self, tryList) {
  var generator = outerFn ? Object.create(outerFn.prototype) : this;
  var context = new Context(tryList);
  var state = GenStateSuspendedStart;

  function invoke(method, arg) {
    if (state === GenStateExecuting) {
      throw new Error("Generator is already running");
    }

    if (state === GenStateCompleted) {
      throw new Error("Generator has already finished");
    }

    while (true) {
      var delegate = context.delegate;
      var info;

      if (delegate) {
        try {
          info = delegate.iterator[method](arg);

          // Delegate generator ran and handled its own exceptions so
          // regardless of what the method was, we continue as if it is
          // "next" with an undefined arg.
          method = "next";
          arg = undefined;

        } catch (uncaught) {
          context.delegate = null;

          // Like returning generator.throw(uncaught), but without the
          // overhead of an extra function call.
          method = "throw";
          arg = uncaught;

          continue;
        }

        if (info.done) {
          context[delegate.resultName] = info.value;
          context.next = delegate.nextLoc;
        } else {
          state = GenStateSuspendedYield;
          return info;
        }

        context.delegate = null;
      }

      if (method === "next") {
        if (state === GenStateSuspendedStart &&
            typeof arg !== "undefined") {
          // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-generatorresume
          throw new TypeError(
            "attempt to send " + JSON.stringify(arg) + " to newborn generator"
          );
        }

        if (state === GenStateSuspendedYield) {
          context.sent = arg;
        } else {
          delete context.sent;
        }

      } else if (method === "throw") {
        if (state === GenStateSuspendedStart) {
          state = GenStateCompleted;
          throw arg;
        }

        if (context.dispatchException(arg)) {
          // If the dispatched exception was caught by a catch block,
          // then let that catch block handle the exception normally.
          method = "next";
          arg = undefined;
        }

      } else if (method === "return") {
        context.abrupt("return", arg);
      }

      state = GenStateExecuting;

      try {
        var value = innerFn.call(self, context);

        // If an exception is thrown from innerFn, we leave state ===
        // GenStateExecuting and loop back for another invocation.
        state = context.done ? GenStateCompleted : GenStateSuspendedYield;

        info = {
          value: value,
          done: context.done
        };

        if (value === ContinueSentinel) {
          if (context.delegate && method === "next") {
            // Deliberately forget the last sent value so that we don't
            // accidentally pass it on to the delegate.
            arg = undefined;
          }
        } else {
          return info;
        }

      } catch (thrown) {
        state = GenStateCompleted;

        if (method === "next") {
          context.dispatchException(thrown);
        } else {
          arg = thrown;
        }
      }
    }
  }

  generator.next = invoke.bind(generator, "next");
  generator["throw"] = invoke.bind(generator, "throw");
  generator["return"] = invoke.bind(generator, "return");

  return generator;
}

Gp[iteratorSymbol] = function () {
  return this;
};

Gp.toString = function () {
  return "[object Generator]";
};

function pushTryEntry(triple) {
  var entry = { tryLoc: triple[0] };

  if (1 in triple) {
    entry.catchLoc = triple[1];
  }

  if (2 in triple) {
    entry.finallyLoc = triple[2];
  }

  this.tryEntries.push(entry);
}

function resetTryEntry(entry, i) {
  var record = entry.completion || {};
  record.type = i === 0 ? "normal" : "return";
  delete record.arg;
  entry.completion = record;
}

function Context(tryList) {
  // The root entry object (effectively a try statement without a catch
  // or a finally block) gives us a place to store values thrown from
  // locations where there is no enclosing try statement.
  this.tryEntries = [{ tryLoc: "root" }];
  tryList.forEach(pushTryEntry, this);
  this.reset();
}

runtime.keys = function (object) {
  var keys = [];
  for (var key in object) {
    keys.push(key);
  }
  keys.reverse();

  // Rather than returning an object with a next method, we keep
  // things simple and return the next function itself.
  return function next() {
    while (keys.length) {
      var key = keys.pop();
      if (key in object) {
        next.value = key;
        next.done = false;
        return next;
      }
    }

    // To avoid creating an additional object, we just hang the .value
    // and .done properties off the next function object itself. This
    // also ensures that the minifier will not anonymize the function.
    next.done = true;
    return next;
  };
};

function values(iterable) {
  var iterator = iterable;
  if (iteratorSymbol in iterable) {
    iterator = iterable[iteratorSymbol]();
  } else if (!isNaN(iterable.length)) {
    var i = -1;
    iterator = function next() {
      while (++i < iterable.length) {
        if (i in iterable) {
          next.value = iterable[i];
          next.done = false;
          return next;
        }
      }
      next.done = true;
      return next;
    };
    iterator.next = iterator;
  }
  return iterator;
}
runtime.values = values;

Context.prototype = {
  constructor: Context,

  reset: function () {
    this.prev = 0;
    this.next = 0;
    this.sent = undefined;
    this.done = false;
    this.delegate = null;

    this.tryEntries.forEach(resetTryEntry);

    // Pre-initialize at least 20 temporary variables to enable hidden
    // class optimizations for simple generators.
    for (var tempIndex = 0, tempName;
         hasOwn.call(this, tempName = "t" + tempIndex) || tempIndex < 20;
         ++tempIndex) {
      this[tempName] = null;
    }
  },

  stop: function () {
    this.done = true;

    var rootEntry = this.tryEntries[0];
    var rootRecord = rootEntry.completion;
    if (rootRecord.type === "throw") {
      throw rootRecord.arg;
    }

    return this.rval;
  },

  dispatchException: function (exception) {
    if (this.done) {
      throw exception;
    }

    var context = this;
    function handle(loc, caught) {
      record.type = "throw";
      record.arg = exception;
      context.next = loc;
      return !!caught;
    }

    for (var i = this.tryEntries.length - 1; i >= 0; --i) {
      var entry = this.tryEntries[i];
      var record = entry.completion;

      if (entry.tryLoc === "root") {
        // Exception thrown outside of any try block that could handle
        // it, so set the completion value of the entire function to
        // throw the exception.
        return handle("end");
      }

      if (entry.tryLoc <= this.prev) {
        var hasCatch = hasOwn.call(entry, "catchLoc");
        var hasFinally = hasOwn.call(entry, "finallyLoc");

        if (hasCatch && hasFinally) {
          if (this.prev < entry.catchLoc) {
            return handle(entry.catchLoc, true);
          } else if (this.prev < entry.finallyLoc) {
            return handle(entry.finallyLoc);
          }

        } else if (hasCatch) {
          if (this.prev < entry.catchLoc) {
            return handle(entry.catchLoc, true);
          }

        } else if (hasFinally) {
          if (this.prev < entry.finallyLoc) {
            return handle(entry.finallyLoc);
          }

        } else {
          throw new Error("try statement without catch or finally");
        }
      }
    }
  },

  _findFinallyEntry: function (finallyLoc) {
    for (var i = this.tryEntries.length - 1; i >= 0; --i) {
      var entry = this.tryEntries[i];
      if (entry.tryLoc <= this.prev &&
          hasOwn.call(entry, "finallyLoc") && (
            entry.finallyLoc === finallyLoc ||
            this.prev < entry.finallyLoc)) {
        return entry;
      }
    }
  },

  abrupt: function (type, arg) {
    var entry = this._findFinallyEntry();
    var record = entry ? entry.completion : {};

    record.type = type;
    record.arg = arg;

    if (entry) {
      this.next = entry.finallyLoc;
    } else {
      this.complete(record);
    }

    return ContinueSentinel;
  },

  complete: function (record) {
    if (record.type === "throw") {
      throw record.arg;
    }

    if (record.type === "break" || record.type === "continue") {
      this.next = record.arg;
    } else if (record.type === "return") {
      this.rval = record.arg;
      this.next = "end";
    }

    return ContinueSentinel;
  },

  finish: function (finallyLoc) {
    var entry = this._findFinallyEntry(finallyLoc);
    return this.complete(entry.completion);
  },

  "catch": function (tryLoc) {
    for (var i = this.tryEntries.length - 1; i >= 0; --i) {
      var entry = this.tryEntries[i];
      if (entry.tryLoc === tryLoc) {
        var record = entry.completion;
        var thrown;
        if (record.type === "throw") {
          thrown = record.arg;
          resetTryEntry(entry, i);
        }
        return thrown;
      }
    }

    // The context.catch method must only be called with a location
    // argument that corresponds to a known catch block.
    throw new Error("illegal catch attempt");
  },

  delegateYield: function (iterable, resultName, nextLoc) {
    this.delegate = {
      iterator: values(iterable),
      resultName: resultName,
      nextLoc: nextLoc
    };

    return ContinueSentinel;
  }
};