Bug 176685 – Safari 10 /11 problem with if (!await get(something)).

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

This code doesn't work in Safari (10 and 11, with Technology preview 39a), it blocks page rendering and says::

if(!await a(t, "myPromise").content) {
console.log('ByBye');
}

Of course if I remove await from my source code or check it like this:

if (myPromiseContent === 0) {

it works again.

But I can't use "!" with an await? Is it generally wrong? "eslint" doesn't warn me about this.

Am I wrong?

[Alexey Proskuryakov]

Could you please attach a complete reproducible test case?

[GSkachkov]

Will look to this issue

[GSkachkov]

I'm receiving error in following script:
```
(async () => { 
     var obj = { content: Promise.resolve('abc') }; 
     var a = !await obj.content; 
     console.log(a); 
})();
// SyntaxError: Unexpected identifier 'obj'. Expected ';' after variable declaration.
```
Work well if wraps await in parentheses:
```
(async () => { 
     var obj = { content: Promise.resolve('abc') }; 
     var a = !(await obj.content); 
     console.log(a); 
})();
```

[GSkachkov]

Created attachment 322700 [details]
Patch

WiP. Need more tests

[GSkachkov]

Created attachment 322850 [details]
Patch

Patch

[Saam Barati]

Comment on attachment 322850 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=322850&action=review

> Source/JavaScriptCore/parser/Parser.cpp:4447
> +        else if (currentFunctionScope()->isAsyncFunctionBoundary())

Is this the grammar that is specified?

[GSkachkov]

Comment on attachment 322850 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=322850&action=review

I think I'll update ChangeLog description to the link of the spec

>> Source/JavaScriptCore/parser/Parser.cpp:4447
>> +        else if (currentFunctionScope()->isAsyncFunctionBoundary())
> 
> Is this the grammar that is specified?

This is how I understand Note 1 in https://tc39.github.io/ecma262/#sec-async-function-definitions:

```
AsyncFunctionBody:
          FunctionBody[~Yield, +Await]

AwaitExpression[Yield]:
          awaitUnaryExpression[?Yield, +Await]

Note 1
await is parsed as an AwaitExpression when the [Await] parameter is present. The [Await] parameter is present in the following contexts:
In an AsyncFunctionBody.
In the FormalParameters of an AsyncFunctionDeclaration and AsyncFunctionExpression. AwaitExpression in this position is a Syntax error via static semantics.
```
I hope this is  correct understanding of the spec.

[GSkachkov]

Created attachment 323048 [details]
Patch

Fix ChangeLog description

[WebKit Commit Bot]

Comment on attachment 323048 [details]
Patch

Clearing flags on attachment: 323048

Committed r223043: <http://trac.webkit.org/changeset/223043>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/34882523>

[Ryan Haddad]

This change caused 32 test262 "failures" which are seemingly unexpected passes:

test262.yaml/test262/test/language/expressions/async-arrow-function/await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/async-function/await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/async-function/await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/async-function/named-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/async-function/named-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/async-generator/await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/async-generator/await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/async-generator/named-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/async-generator/named-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/class/async-gen-method-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/class/async-gen-method-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/class/async-gen-method-static-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/class/async-gen-method-static-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/class/async-method-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/class/async-method-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/class/async-method-static-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/class/async-method-static-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/object/method-definition/async-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/object/method-definition/async-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/object/method-definition/async-gen-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/expressions/object/method-definition/async-gen-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/async-function/await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/async-function/await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/async-generator/await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/async-generator/await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/class/async-gen-method-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/class/async-gen-method-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/class/async-gen-method-static-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/class/async-gen-method-static-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/class/async-method-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/class/async-method-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/class/async-method-static-await-as-identifier-reference.js.default-strict: ERROR: Unexpected exit code: 0
test262.yaml/test262/test/language/statements/class/async-method-static-await-as-identifier-reference.js.default: ERROR: Unexpected exit code: 0

https://build.webkit.org/builders/Apple%20El%20Capitan%20Release%20Test262%20%28Tests%29/builds/4709

I will update the expectations.

[Ryan Haddad]

(In reply to Ryan Haddad from comment #12)
> I will update the expectations.
Done in https://trac.webkit.org/changeset/223067/webkit

[Alexey Shvayka]

*** Bug 177851 has been marked as a duplicate of this bug. ***