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"await is only valid in async function" when trying to use await in a for loop with TLA support #32708
Description
- Version: 12.14.1
- Platform: macOS 10.14.x
- Subsystem:
What steps will reproduce the bug?
I run node with TLA support flag, I don't get the error if I do await on a top-level, but I do get the error if I do it in a for loop.
How often does it reproduce? Is there a required condition?
$ node --experimental-repl-await
Welcome to Node.js v12.8.1.
Type ".help" for more information.
> const timeout = delay => new Promise((res) => setTimeout(res, delay));
undefined
> timeout(1000).then(() => console.log('aaa'))
Promise { <pending> }
> aaa // this is displayed after 1 second, so it's fine
> await timeout(1000);
undefined // this is executed after 1 second, so it's also fine
> for (const i of [1, 2, 3]) {
... await timeout(1000);
Thrown:
await timeout(1000);
^^^^^
SyntaxError: await is only valid in async function
>
What is the expected behavior?
No error.
What do you see instead?
Error, see above.
Activity
hassaanp commentedon Apr 7, 2020
I think the issue is due to a premature error check that runs before the code block is allowed to be closed.
If you instead write:
It should work as expected.
serge1peshcoff commentedon Apr 7, 2020
@hassaanp yeah I've also just discovered it while trying to reproduce. Do you consider this a bug?
serge1peshcoff commentedon Apr 7, 2020
@hassaanp actually it can be that it's not only repl issue, this is the example that doesn't use repl and still fails (both with for...of loop written with 1 and 3 lines):
hassaanp commentedon Apr 7, 2020
I don't believe this is a bug.
From what I understand, repl behavior is configured by the
--experimental-repl-awaitflag.Using
awaitin a node.js application is only allowed inside an async function. When you execute the filetest.js, the--experimental-repl-awaitflag should not affect it since it runs like any standard node.js application.I could be wrong. Maybe other contributors can chip in.
serge1peshcoff commentedon Apr 7, 2020
@hassaanp yeah but also
node --experimental-repl-await test.jsallowsawaitstatements on the top level (not within loops)devsnek commentedon Apr 7, 2020
There is more general work to move towards a new method of evaluating repl input (using v8 inspector apis), which would fix a number of things, including handling TLA. because of that, i don't think anyone is specifically working on making our acorn parser hacks work better.
serge1peshcoff commentedon Apr 7, 2020
@devsnek is there an open issue on it? if so, I'd rather close this as part of it and subscribe to it instead
devsnek commentedon Apr 7, 2020
@serge1peshcoff v8:6903
BridgeAR commentedon Nov 29, 2021
This is working in newer Node.js versions. Closing.