Test cases for async function and async generator edge-cases

test/language/statements/async-generator/return-undefined-implicit-and-explicit.js

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+// Copyright (C) 2019 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-return-statement-runtime-semantics-evaluation
+description: >
+ Return with an explicit return value awaits this value.
+info: |
+ 13.10.1 Runtime Semantics: Evaluation
+
+ ReturnStatement : return;
+ 1. Return Completion { [[Type]]: return, [[Value]]: undefined, [[Target]]: empty }.
+
+ ReturnStatement : return Expression ;
+ 1. Let exprRef be the result of evaluating Expression.
+ 2. Let exprValue be ? GetValue(exprRef).
+ 3. If ! GetGeneratorKind() is async, set exprValue to ? Await(exprValue).
+ 4. Return Completion { [[Type]]: return, [[Value]]: exprValue, [[Target]]: empty }.
+
+ 25.5.3.2 AsyncGeneratorStart ( generator, generatorBody )
+
+ ...
+ 5. Set the code evaluation state of genContext such that when evaluation is resumed for that
+ execution context the following steps will be performed:
+ a. Let result be the result of evaluating generatorBody.
+ ...
+ e. If result is a normal completion, let resultValue be undefined.
+ ...
+ g. Return ! AsyncGeneratorResolve(generator, resultValue, true).
+
+includes: [compareArray.js]
+flags: [async]
+features: [async-iteration]
+---*/
+
+// 25.5.3.2, step 5.e: |generatorBody| execution ends with a normal completion.
+async function* g1() {
+ // no return
+}
+
+// 13.10.1: No expression form means direct return.
+async function* g2() {
+ return;
+}
+
+// 13.10.1: Explicit expression requires Await.
+async function* g3() {
+ return undefined; // Return undefined via global value `undefined`.
+}
+
+// 13.10.1: Explicit expression requires Await.
+async function* g4() {
+ return void 0; // Return undefined via void expression.
+}
+
+var expected = [
+ "tick 1",
+
+ "g1 ret",
+ "g2 ret",
+
+ "tick 2",
+
+ "g3 ret",
+ "g4 ret",
+];
+
+var actual = [];
+
+Promise.resolve(0)
+ .then(() => actual.push("tick 1"))
+ .then(() => actual.push("tick 2"))
+ .then(() => {
+ assert.compareArray(actual, expected, "Ticks for implicit and explicit return undefined");
+}).then($DONE, $DONE);
+
+g1().next().then(v => actual.push("g1 ret"));
+g2().next().then(v => actual.push("g2 ret"));
+g3().next().then(v => actual.push("g3 ret"));
+g4().next().then(v => actual.push("g4 ret"));

test/language/statements/async-generator/yield-return-then-getter-ticks.js

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+// Copyright (C) 2019 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-generator-function-definitions-runtime-semantics-evaluation
+description: >
+ Return resumption value is awaited upon and hence is treated as a thenable.
+info: |
+ 14.4.14 Runtime Semantics: Evaluation
+ YieldExpression : yield AssignmentExpression
+
+ ...
+ 3. Let value be ? GetValue(exprRef).
+ 4. If generatorKind is async, then return ? AsyncGeneratorYield(value).
+ ...
+
+ 25.5.3.7 AsyncGeneratorYield ( value )
+ ...
+ 5. Set value to ? Await(value).
+ ...
+ 8. Set the code evaluation state of genContext such that when evaluation is resumed with a
+ Completion resumptionValue the following steps will be performed:
+ ...
+ b. Let awaited be Await(resumptionValue.[[Value]]).
+ ...
+ e. Return Completion { [[Type]]: return, [[Value]]: awaited.[[Value]], [[Target]]: empty }.
+ ...
+
+ 6.2.3.1 Await
+ ...
+ 2. Let promise be ? PromiseResolve(%Promise%, « value »).
+ ...
+
+ 25.6.4.5.1 PromiseResolve ( C, x )
+ ...
+ 3. Let promiseCapability be ? NewPromiseCapability(C).
+ 4. Perform ? Call(promiseCapability.[[Resolve]], undefined, « x »).
+ ...
+
+ 25.6.1.5 NewPromiseCapability ( C )
+ ...
+ 7. Let promise be ? Construct(C, « executor »).
+ ...
+
+ 25.6.3.1 Promise ( executor )
+ ...
+ 8. Let resolvingFunctions be CreateResolvingFunctions(promise).
+ ...
+
+ 25.6.1.3 CreateResolvingFunctions ( promise )
+ ...
+ 2. Let stepsResolve be the algorithm steps defined in Promise Resolve Functions (25.6.1.3.2).
+ 3. Let resolve be CreateBuiltinFunction(stepsResolve, « [[Promise]], [[AlreadyResolved]] »).
+ ...
+
+ 25.6.1.3.2 Promise Resolve Functions
+ ...
+ 9. Let then be Get(resolution, "then").
+ ...
+
+includes: [compareArray.js]
+flags: [async]
+features: [async-iteration]
+---*/
+
+var expected = [
+ "start",
+
+ // `Await(value)` promise resolved.
+ "tick 1",
+
+ // "then" of `resumptionValue.[[Value]]` accessed.
+ "get then",
+
+ // `Await(resumptionValue.[[Value]])` promise resolved.
+ "tick 2",
+];
+
+var actual = [];
+
+async function* f() {
+ actual.push("start");
+ yield 123;
+ actual.push("stop - never reached");
+}
+
+Promise.resolve(0)
+ .then(() => actual.push("tick 1"))
+ .then(() => actual.push("tick 2"))
+ .then(() => {
+ assert.compareArray(actual, expected, "Ticks for return with thenable getter");
+}).then($DONE, $DONE);
+
+var it = f();
+
+// Start generator execution.
+it.next();
+
+// Stop generator execution.
+it.return({
+ get then() {
+ actual.push("get then");
+ }
+});

test/language/statements/async-generator/yield-star-async-from-sync-iterator-inaccessible.js

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+// Copyright (C) 2019 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-createasyncfromsynciterator
+description: >
+ Async-from-Sync Iterator instances are not accessible from user code.
+info: |
+ 25.1.4.1 CreateAsyncFromSyncIterator ( syncIteratorRecord )
+ 1. Let asyncIterator be ! ObjectCreate(%AsyncFromSyncIteratorPrototype%, « [[SyncIteratorRecord]] »).
+ 2. Set asyncIterator.[[SyncIteratorRecord]] to syncIteratorRecord.
+ 3. Let nextMethod be ! Get(asyncIterator, "next").
+ 4. Let iteratorRecord be Record { [[Iterator]]: asyncIterator, [[NextMethod]]: nextMethod, [[Done]]: false }.
+ 5. Return iteratorRecord.
+
+ 14.4.14 Runtime Semantics: Evaluation
+ YieldExpression : yield * AssignmentExpression
+ 1. Let generatorKind be ! GetGeneratorKind().
+ ...
+ 4. Let iteratorRecord be ? GetIterator(value, generatorKind).
+ ...
+
+ 7.4.1 GetIterator ( obj [ , hint [ , method ] ] )
+ ...
+ 3. If method is not present, then
+ a. If hint is async, then
+ i. Set method to ? GetMethod(obj, @@asyncIterator).
+ ii. If method is undefined, then
+ 1. Let syncMethod be ? GetMethod(obj, @@iterator).
+ 2. Let syncIteratorRecord be ? GetIterator(obj, sync, syncMethod).
+ 3. Return ? CreateAsyncFromSyncIterator(syncIteratorRecord).
+ ...
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var AsyncIteratorPrototype = Object.getPrototypeOf(async function*(){}.constructor.prototype.prototype);
+
+Object.defineProperty(AsyncIteratorPrototype, Symbol.iterator, {
+ get() {
+ throw new Error("@@iterator accessed");
+ }
+});
+
+Object.defineProperty(AsyncIteratorPrototype, Symbol.asyncIterator, {
+ get() {
+ throw new Error("@@asyncIterator accessed");
+ }
+});
+
+async function* g() {
+ yield* [];
+}
+g().next().then(() => $DONE(), $DONE);

test/language/statements/async-generator/yield-star-normal-notdone-iter-value-throws.js

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+// Copyright (C) 2019 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-generator-function-definitions-runtime-semantics-evaluation
+description: >
+ Abrupt completion when calling IteratorValue is propagated when received.[[Type]] is normal.
+info: |
+ 14.4.14 Runtime Semantics: Evaluation
+ YieldExpression : yield* AssignmentExpression
+
+ ...
+ 7. Repeat,
+ a. If received.[[Type]] is normal, then
+ ...
+ vi. If generatorKind is async, then set received to AsyncGeneratorYield(? IteratorValue(innerResult)).
+ ...
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var token = {};
+
+var asyncIter = {
+ [Symbol.asyncIterator]() {
+ return this;
+ },
+ next() {
+ return {
+ done: false,
+ get value() {
+ throw token;
+ }
+ };
+ }
+};
+
+async function* f() {
+ var thrown;
+ try {
+ yield* asyncIter;
+ } catch (e) {
+ thrown = e;
+ }
+ return thrown;
+}
+
+var iter = f();
+
+iter.next().then(({value}) => {
+ assert.sameValue(value, token);
+}).then($DONE, $DONE);

test/language/statements/async-generator/yield-star-return-notdone-iter-value-throws.js

@@ -0,0 +1,63 @@
+// Copyright (C) 2019 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-generator-function-definitions-runtime-semantics-evaluation
+description: >
+ Abrupt completion when calling IteratorValue is propagated when received.[[Type]] is return.
+info: |
+ 14.4.14 Runtime Semantics: Evaluation
+ YieldExpression : yield* AssignmentExpression
+
+ ...
+ 7. Repeat,
+ ...
+ c. Else,
+ i. Assert: received.[[Type]] is return.
+ ...
+ ix. If generatorKind is async, then set received to AsyncGeneratorYield(? IteratorValue(innerReturnResult)).
+ ...
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var token = {};
+
+var asyncIter = {
+ [Symbol.asyncIterator]() {
+ return this;
+ },
+ next() {
+ return {
+ done: false,
+ value: undefined,
+ };
+ },
+ return() {
+ return {
+ done: false,
+ get value() {
+ throw token;
+ }
+ };
+ }
+};
+
+async function* f() {
+ var thrown;
+ try {
+ yield* asyncIter;
+ } catch (e) {
+ thrown = e;
+ }
+ return thrown;
+}
+
+var iter = f();
+
+iter.next().then(() => {
+ iter.return().then(({value}) => {
+ assert.sameValue(value, token);
+ }).then($DONE, $DONE);
+}).catch($DONE);