1512292 - [meta] Better stacks in debugger when paused in async code

Status: RESOLVED DUPLICATE of bug 1523865

(DevTools :: Debugger, enhancement)

Description

[Jason Orendorff [:jorendorff]]

1.  Suppose an async function g does `await f()`.  f is an async function.

    In a later tick, the debugger breaks in f. Only one frame is on the stack
    (the frame for f), but the debugger should show:

        f()
        ------------ async boundary
        g()


2.  Or, if g in turn was called with `await g()` from another async function h,
    then we should show that too:

        f()
        ------------ async boundary
        g()
        h()

    (Maybe with another async boundary; that's a UI decision we can defer.)

3.  Another test case: g does `await f().then(m);`. The debugger should show:

        f()
        ------------ async boundary
        m()
        g()

Comment 1

[Jason Orendorff [:jorendorff]]

What is hard here?

- Identifying and documenting cases to test (but here we have 3 of them to start with)

- Decrypting the promise object graph
    - Exposing all the bits required via Debugger
    - Implementing this in the server and making it maintainable

- Determining how the server should present it to the client
    - Need a way to express "async boundary"
    - Need a way to express "this is like a call frame, only we're going to call it when we get to it (relax, this is fine)"