Vscode: Support for top-level await operators

[jdavis61]

Will VS Code ever support the ability to execute top-level await operators in the debug console? Currently if you try to execute await outside of an IIFE you will receive the "unexpected indentifer message". Or is there a way to resolve the promise in the IIFE?

My hope is someday the new chrome dev tools functionality may be added to WebStorm. https://developers.google.com/web/updates/2017/08/devtools-release-notes#await

• VSCode Version: 1.18.0
• OS Version: Windows 10

Steps to Reproduce:

1. Open the attached code in VSCode. Set a debug break point at line 7.
2. Click Debug then Start Debbuging. In the debug console type "await testFunction(); " then press enter. SyntaxError: Unexpected identifier appears in the Debug Console.
3. In the debug console, type "(async () => { await testFunction();} )();" then press enter. Promise { pending } appears.

async function testFunction() {
    return new Promise((resolve) => {
        resolve('test');
    });
}

testFunction().then((res) => {
    console.log(res);
});

[weinand]

Node-debug doesn't preprocess the user input in any way before sending it to node.js for evaluation.
So, what you are seeing is expected but I understand it would be nice if VS Code could wrap the expression automagically into a closure.
On the other hand this "magic" could result in strange bugs that are difficult to diagnose.

@roblourens ?

[roblourens]

I believe this will come automatically with newer Chrome and Node versions. Will leave this open on myself to test and verify.

[roblourens]

Chrome sends "(async () => {return (await Promise.resolve('hi'))})()", but the adapter needs to know that it's attached to an appropriate version of Node/Chrome.

[auchenberg]

So the Chrome DevTools front-end sends a special formatted expression for top-level operators @roblourens?

[roblourens]

Right

[laggingreflex]

Does the recently introduced experimental-repl-await in node v10 help with this?

[roblourens]

Probably but it's not necessarily any easier than what I said before.

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[roblourens]

This is actually a fairly easy vscode-chrome-debug-core feature request. I filed https://github.com/Microsoft/vscode-chrome-debug-core/issues/353

[roblourens]

I would take a PR for this. The change will be entirely inside the debug adapter, see https://github.com/Microsoft/vscode-chrome-debug-core/issues/353 and https://github.com/Microsoft/vscode-node-debug2/blob/master/CONTRIBUTING.md

[connor4312]

This appears to happen in the latest stable Chrome (77) and Node.js (12.11) versions.

await Promise.resolve('foo')
SyntaxError: await is only valid in async function

It appears that the Chrome console preprocesses expressions that contain await (if the results here have anything returned from this function), so unfortunately this does not look super trivial to do. I think it'd be appropriate for us to preprocess console input in the same way, as I imagine that most users will expect the debug console in VS Code to behave identically to the one in Chrome.

[merqrial]

...waits patiently...

[jcrben]

I noticed the below over at https://github.com/microsoft/vscode-js-debug

I tried it with https://github.com/request/request-promise-native but not sure how to resolve the promise:

[connor4312]

@jcrben this happens because Chrome/V8 does not let us await if you're paused on a breakpoint. If you're not on a breakpoint and running normally, we can evaluate the given statement(s) and get the promise result back.

[galkowskit]

This is becoming more and more relevant. Deno (a TypeScript runtime) now supports top-level await.

[roblourens]

I'll call this closed based on the fact that it's supported in https://github.com/microsoft/vscode-js-debug (as good as the runtime lets us) and that is the future of JS debugging

[jcrben]

@roblourens @connor4312 is the plan to at some point be able to use this when paused at a breakpoint? That's where I see this as being the most useful.

[connor4312]

You can follow this Chromium issue for that, Ben: https://bugs.chromium.org/p/chromium/issues/detail?id=833928