babel/packages/babel-plugin-transform-regenerator/test/regenerator-fixtures/async.js

/**
 * Copyright (c) 2014-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

var assert = require("assert");

assert(
  function* () {}.toString().indexOf("regenerator") !== -1,
  "regenerator-transform should be enabled",
);

describe("async functions and await expressions", function () {
  describe("no-await async function", function () {
    it("should return a Promise", function (done) {
      var called = false;

      async function noAwait(value) {
        called = true;
        return value;
      }

      var promise = noAwait("asdf");
      assert.strictEqual(called, true);

      promise
        .then(function (value) {
          assert.strictEqual(called, true);
          assert.strictEqual(value, "asdf");
          done();
        })
        .catch(done);
    });
  });

  describe("one-await async function", function () {
    it("should finish asynchronously", function (done) {
      var flag1 = false;
      var flag2 = false;

      async function oneAwait(value) {
        flag1 = true;
        var result = await value;
        flag2 = true;
        return result;
      }

      var promise = oneAwait("asdf");
      assert.strictEqual(flag1, true);
      assert.strictEqual(flag2, false);

      promise
        .then(function (value) {
          assert.strictEqual(flag2, true);
          assert.strictEqual(value, "asdf");
          done();
        })
        .catch(done);
    });
  });

  describe("nested async function calls", function () {
    it("should evaluate in the right order", function (done) {
      var markers = [];

      async function innerMost(marker) {
        markers.push(marker);
        return await marker;
      }

      async function inner(marker) {
        markers.push(marker);

        assert.strictEqual(await innerMost(marker + 1), marker + 1);

        markers.push(marker + 2);

        assert.strictEqual(await innerMost(marker + 3), marker + 3);

        markers.push(marker + 4);
      }

      async function outer() {
        markers.push(0);
        await inner(1);
        markers.push(6);
        await inner(7);
        markers.push(12);
      }

      outer()
        .then(function () {
          var expected = [];
          for (var i = 0; i <= 12; ++i) expected.push(i);
          assert.deepEqual(markers, expected);
          done();
        })
        .catch(done);
    });
  });

  describe("dependent promises", function () {
    it("should be awaitable out of order", function (done) {
      async function outer(value) {
        var resolved = false;
        var p1 = new Promise(function (resolve) {
          setTimeout(function () {
            resolve(value + 1);
            resolved = true;
          }, 0);
        });

        assert.strictEqual(resolved, false);

        var v2 = await p1.then(function (value) {
          return value + 1;
        });

        assert.strictEqual(resolved, true);

        var v1 = await p1;

        return [v1, v2];
      }

      outer(1)
        .then(function (pair) {
          assert.deepEqual(pair, [2, 3]);
          done();
        })
        .catch(done);
    });
  });

  describe("rejected promises", function () {
    it("should cause await expressions to throw", function (done) {
      var error = new Error("rejected");

      async function f(arg) {
        try {
          return await arg;
        } catch (e) {
          assert.strictEqual(e, error);
          return "did throw";
        }
      }

      Promise.all([
        f(Promise.reject(error)),
        f(Promise.resolve("did not throw")),
      ])
        .then(function (results) {
          assert.deepEqual(results, ["did throw", "did not throw"]);
          done();
        })
        .catch(done);
    });

    it("should be returned by exceptional async functions", function (done) {
      var error = new Error("rejected");

      async function e(arg) {
        if (arg) {
          throw arg;
        }
        return "did not throw";
      }

      async function f(arg) {
        return await e(arg);
      }

      async function g(arg) {
        return await f(arg);
      }

      async function h(arg) {
        return await Promise.all([g(arg), Promise.resolve("dummy")]);
      }

      Promise.all([
        h(error).then(
          function () {
            done(new Error("should not have resolved"));
          },
          function (e) {
            assert.strictEqual(e, error);
            return "ok1";
          },
        ),
        h(null).then(function (result) {
          assert.deepEqual(result, ["did not throw", "dummy"]);
          return "ok2";
        }),
      ])
        .then(function (results) {
          assert.deepEqual(results, ["ok1", "ok2"]);
          done();
        })
        .catch(done);
    });

    it("should propagate failure when returned", function () {
      var rejection = new Error("rejection");

      async function f() {
        return new Promise(function (resolve, reject) {
          reject(rejection);
        });
      }

      return f().then(
        function (result) {
          assert.ok(false, "should have been rejected");
        },
        function (error) {
          assert.strictEqual(error, rejection);
        },
      );
    });
  });

  describe("async function expressions", function () {
    it("should be allowed", function (done) {
      (async function (arg) {
        return await arg;
      })(Promise.resolve(1234))
        .then(function (value) {
          assert.strictEqual(value, 1234);
          done();
        })
        .catch(done);
    });
  });

  describe("the this object", function () {
    it("should default to undefined (strict)", function (done) {
      async function f() {
        "use strict";

        return this;
      }

      f()
        .then(function (value) {
          assert.strictEqual(value, undefined);
          done();
        })
        .catch(done);
    });

    it("should respect .call's this", function (done) {
      async function f() {
        return this;
      }

      var self = {};
      f.call(self)
        .then(function (value) {
          assert.strictEqual(value, self);
          done();
        })
        .catch(done);
    });

    it("shouldn't capture this when not needed", function () {
      // https://github.com/babel/babel/issues/4056

      async function f() {
        return 0;
      }

      var source = String(f);
      assert.strictEqual(source.indexOf("this"), -1);
    });
  });
});

describe("async generator functions", function () {
  // Transforming this currently leaves behind a `regeneratorRuntime` reference,
  // rather than referencing the helper.
  it.skip("should return a working AsyncIterator", function () {
    var markers = [];

    async function* gen(arg) {
      markers.push(0);
      var sent = yield arg;
      markers.push(1);
      var result = await sent;
      markers.push(2);
      assert.strictEqual(await (yield "second"), "sent after second");
      markers.push(3);
      return result;
    }

    var iter = gen("initial argument");
    assert.deepEqual(markers, []);

    var firstPromise = iter.next();
    assert.deepEqual(markers, [0]);

    return firstPromise
      .then(function (firstResult) {
        assert.deepEqual(firstResult, {
          value: "initial argument",
          done: false,
        });

        assert.deepEqual(markers, [0]);

        return iter.next(
          new Promise(function (resolve) {
            setTimeout(resolve, 100);
          }).then(function () {
            assert.deepEqual(markers, [0, 1]);
            return "will become final result";
          }),
        );
      })
      .then(function (secondResult) {
        assert.deepEqual(secondResult, {
          value: "second",
          done: false,
        });

        assert.deepEqual(markers, [0, 1, 2]);

        return iter.next("sent after second");
      })
      .then(function (finalResult) {
        assert.deepEqual(markers, [0, 1, 2, 3]);
        assert.deepEqual(finalResult, {
          value: "will become final result",
          done: true,
        });
      });
  });

  it("should keep results in order", function () {
    async function* range(limit) {
      var before = [];
      var after = [];
      for (var i = 0; i < limit; ++i) {
        before.push(i);
        yield i;
        after.push(i);
      }
      assert.deepEqual(before, after);
      return before;
    }

    var limit = 10;
    var iter = range(limit);
    var promises = [];
    var results = [];

    for (var i = 0; i < limit; ++i) {
      var promise = iter.next();
      promises.push(promise);

      promise.then(function (result) {
        assert.strictEqual(result.done, false);
        results.push(result);
      });
    }

    assert.deepEqual(results, []);

    return Promise.all(promises)
      .then(function (promiseResults) {
        assert.deepEqual(results, promiseResults);

        return iter.next();
      })
      .then(function (finalResult) {
        assert.deepEqual(
          results.map(function (result) {
            return result.value;
          }),
          finalResult.value,
        );

        assert.strictEqual(finalResult.done, true);
      });
  });

  it("should be able to handle many awaits", function () {
    var awaitCount = 0;

    function countAwait(i) {
      return Promise.resolve(i).then(function () {
        ++awaitCount;
      });
    }

    async function* gen(limit) {
      await countAwait(0);
      yield 1;
      await countAwait(2);
      await countAwait(3);
      yield 4;
      await countAwait(5);
      await countAwait(6);
      await countAwait(7);
      yield 8;
      for (var i = 0; i < limit; ++i) {
        await countAwait(i);
      }
      return "done";
    }

    var iter = gen(100);

    return iter
      .next()
      .then(function (result) {
        assert.strictEqual(awaitCount, 1);

        assert.deepEqual(result, {
          value: 1,
          done: false,
        });

        return iter.next();
      })
      .then(function (result) {
        assert.strictEqual(awaitCount, 3);

        assert.deepEqual(result, {
          value: 4,
          done: false,
        });

        return iter.next();
      })
      .then(function (result) {
        assert.strictEqual(awaitCount, 6);

        assert.deepEqual(result, {
          value: 8,
          done: false,
        });

        return iter.next();
      })
      .then(function (result) {
        assert.strictEqual(awaitCount, 6 + 100);

        assert.deepEqual(result, {
          value: "done",
          done: true,
        });

        return iter.next();
      })
      .then(function (result) {
        assert.deepEqual(result, {
          value: void 0,
          done: true,
        });
      });
  });

  it("should not propagate exceptions between iterations", function () {
    async function* gen() {
      yield 1;
      yield 2;
    }

    var iter = gen();

    return iter
      .next()
      .then(function (result) {
        assert.deepEqual(result, {
          value: 1,
          done: false,
        });

        return iter.throw(new Error("thrown from first yield"));
      })
      .then(
        function () {
          throw new Error("should have thrown");
        },
        function (error) {
          assert.strictEqual(error.message, "thrown from first yield");
          return iter.next();
        },
      )
      .then(function (result) {
        assert.deepEqual(result, {
          value: void 0,
          done: true,
        });
      });
  });

  it("should allow yielding a rejected Promise", function () {
    var yielded = new Error("yielded rejection");
    var returned = new Error("returned rejection");

    async function* gen() {
      assert.strictEqual(yield "first yielded", "first sent");
      try {
        assert.strictEqual(yield Promise.reject(yielded), "not reached");
      } catch (e) {
        assert.strictEqual(yield e, "second sent");
        return Promise.reject(returned);
      }
    }

    var iter = gen();

    return iter
      .next()
      .then(function (result) {
        assert.deepEqual(result, {
          value: "first yielded",
          done: false,
        });
        return iter.next("first sent");
      })
      .then(function (result) {
        assert.deepEqual(result, {
          value: yielded,
          done: false,
        });
        return iter.next("second sent");
      })
      .then(
        function (result) {
          assert.ok(false, "should have returned a rejected Promise");
        },
        function (error) {
          assert.strictEqual(error, returned);
        },
      );
  });

  it("should work with nested arrow functions", async function () {
    var a = async b => {
      return await (async () => {
        return await b();
      })();
    };

    assert.strictEqual(await a(() => Promise.resolve(1234)), 1234);
  });

  it("should support super.method(...) in async methods", async function () {
    class A {
      async method() {
        return "from A";
      }
    }

    class B extends A {
      async method() {
        return "from B " + (await super.method());
      }
    }

    assert.strictEqual(await new B().method(), "from B from A");
  });
});

describe("update operators", function () {
  it("should read left side before yielding", function () {
    let x = 0;

    function* test() {
      x += yield;
    }

    var gen = test();
    gen.next();
    x += 1;
    assert.strictEqual(x, 1);

    gen.next(2);
    assert.strictEqual(x, 2);
  });

  it("should explode left side before yielding", function () {
    let obj = { count: 0 };

    function* test() {
      obj[yield "key"] += yield "value";
    }

    var gen = test();

    assert.deepEqual(gen.next(), { value: "key", done: false });
    assert.strictEqual(obj.count, 0);

    assert.deepEqual(gen.next("count"), { value: "value", done: false });
    assert.strictEqual(obj.count, 0);

    obj.count += 1;
    assert.strictEqual(obj.count, 1);

    assert.deepEqual(gen.next(2), { value: void 0, done: true });
    assert.strictEqual(obj.count, 2);
  });

  it("should read left side before awaiting", function () {
    let x = 0;

    async function test(val) {
      x += await val;
      return x;
    }

    const promise = test(2);
    x += 1;

    return promise.then(result => {
      assert.strictEqual(result, 2);
    });
  });
});