[Webkit-unassigned] [Bug 146886] Web Inspector: Source links in Event Listeners panel are missing for bound functions

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=146886

--- Comment #3 from Joseph Pecoraro <joepeck at webkit.org> ---
After discussion with Devin, I think what we really want is for getFunctionDetails to provide the complete chain of bound functions. For instance a bound function's target function may itself be a bound function.

You could imagine a chain like this:

    1  function addArguments() {
    2    var sum = 0;
    3    for (var x of arguments) { sum += x; }
    4    return sum;
    5  }
    6  var foo = addArguments.bind(null, 1);
    7  var bar = foo.bind(null, 2);

Where logging `bar` has a chain like this:

    JSBoundFunction (name=bound bound addArguments, location=script.js:7, boundThis=null, boundArguments=[1], scope=...)
      JSBoundFunction (name=bound addArguments, location=script.js:6, boundThis=null, boundArguments=[2], scope=...)
        JSFunction (name=addArguments, location=script.js:1, scope=...)

The frontend should probably get a list of function details about each of these functions in the chain and decide how to display that information. You could think of this as a call stack for the creation of this function and each of its pieces.

Note this chain is always one directional, it cannot be cyclic.

-----

The same data can be useful for backtraces which include bound functions.

For example this test:

    <script>
    function foo() { bar.bind(null)(); }
    function bar() { ({}).x.x; }
    foo();
    </script>

Currently Produces:

    [Error] TypeError: undefined is not an object (evaluating '({}).x.x')
        bar (test.html:2)
        bar
        foo (test.html:1)
        (anonymous function) (test.html:3)

There are a couple things wrong with this. It should produce:

    [Error] TypeError: undefined is not an object (evaluating '({}).x.x')
        bar (test.html:2)
        bound bar (test.html:1)
        foo (test.html:1)
        (global code) (test.html:3)

Note the "bound bar" being the location of the .bind() invocation. It seems JavaScriptCore is not stashing the location this function was created.

-----

So I think in fixing this we should consider consistent displaying of Functions given that any function may be bound and have a chain of origin.

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