[Webkit-unassigned] [Bug 165681] New: Web Inspector: Console could be made useful for very simple await expressions

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=165681

            Bug ID: 165681
           Summary: Web Inspector: Console could be made useful for very
                    simple await expressions
    Classification: Unclassified
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Web Inspector
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: joepeck at webkit.org
                CC: bburg at apple.com, caitp at igalia.com, joepeck at webkit.org,
                    mattbaker at apple.com, nvasilyev at apple.com,
                    sbarati at apple.com, timothy at apple.com,
                    utatane.tea at gmail.com,
                    webkit-bug-importer at group.apple.com

Summary:
Console could be made useful for very simple await expressions

In the console it would be really useful to just type:

    json = await fetch("data.json")

However `await` won't work unless it is inside of an async function. So to do something like this you would need to end up with something like:

    var json; (async function() { json = await fetch("data.json") })();

Or, if await was unavailable, then users would have to:

    var json; fetch("data.json").then((x) => { json = x });

I could see a useful convenience for the Inspector Console to allow you to run await expressions to populate a variable. Typing `x = await fetch("foo.json")` will eventually populate `x`. In practice the populate is almost immediate (JavaScript executes very quickly, and a human types relatively slowly). But it can be a long running operation in which case we could inform the user the value has populated.

    Example input:

        (a) await 10
        (b) json = await fetch("data.json")

    Sample Detection:

        1. Input fail to parse normally.
        2. Input succeed parsing if wrapped in "(async function() {" + input + "})"
        3. If there are multiple `await` expressions, bail.
           - Convenience is meant for something very simple, if you are doing complex code just write the full syntax.
        4. If there was an assignment use the variable name, otherwise use $result.
           - We could even make $result a Console ONLY value like $exception, $0, $1..$99 etc

    Transformation for (a) and (b):

        var $result;
        (async function() {
          $result = await 10;
          console.info("`$result` populated");
        })();

        var json;
        (async function() {
             let start = Date.now();
             json = await fetch("data.json");
             let end = Date.now();
             // If this took more than one second to populate, tell the user it populated.
             if ((end - start) > 1000)
                 console.info("`json` populated");
         })();

What do people think?

Advantages: Let users make use of await expressions in the console to simplify poking around in the console
Disadvantages: Obfuscates the fact that await can only be used in async functions. Can be misleading.
Precedent: We already do a convenience conversion for: `{a:1,b:2}` to `({a:1,b:2})` to produce objects instead of producing a Syntax Error for labelled statements

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