1473473 - Expose isClassConstructor in Debugger.Object

Status: RESOLVED FIXED

(DevTools :: Debugger, enhancement, P2)

Description

[Nicolas Chevobbe [:nchevobbe]]

It would be more helpful if it would return "Class", or if not possible, if we had a `isES6Class` or similar so we can expose such information to the end user (for now we represent classes as functions)

Comment 1

[David Walsh :davidwalsh]

:nchevobbe Do you have a samle snippet or good STR so I can see if a contributor wants to take this?

Comment 2

[Nicolas Chevobbe [:nchevobbe]]

Steps to reproduce

1. Open the console
2. Evaluate the following:

class MyClass {};
MyClass;

Expected results

The result is class MyClass

Actual results

The result is function MyClass()

---

I remember looking into that at some point, and you have to go pretty deep in C++ code to see what's happening.
The underlying issue seems to be that classes are only syntax sugar on top of functions.

The attribute is describe in Debugger.Object.md#65-66

Comment 3

[Nicolas Chevobbe [:nchevobbe]]

If someone wants to give it a try:

The property is retrieved from js/src/debugger/Object.cpp#290-298, using DebuggerObject::getClassName which is defined in js/src/debugger/Object.cpp#1573-1592

That calls GetObjectClassName defined in js/src/vm/JSObject-inl.h#613-620, which seems to use js/src/vm/JSObject.h#106.

Comment 4

[Logan Smyth [:loganfsmyth]]

If we want to do this, I think adding .isClassConstructor would be better than changing .class to return Class. From a runtime perspective, a constructor is just a function.

Implementation-wise, JSFunction objects already have an isClassConstructor() method, so the same way we do the other isX checks for function types should also work here, like https://searchfox.org/mozilla-central/rev/11d9c7b7fa82fdfb8ac2a8f0864e9d8d5fe2b926/js/src/debugger/Object.cpp#1544

Comment 5

[Nicolas Chevobbe [:nchevobbe]]

(In reply to Logan Smyth [:loganfsmyth] from comment #4)

If we want to do this, I think adding .isClassConstructor would be better than changing .class to return Class. From a runtime perspective, a constructor is just a function.

Implementation-wise, JSFunction objects already have an isClassConstructor() method, so the same way we do the other isX checks for function types should also work here, like https://searchfox.org/mozilla-central/rev/11d9c7b7fa82fdfb8ac2a8f0864e9d8d5fe2b926/js/src/debugger/Object.cpp#1544

Awesome! I might give it a try then :)

Comment 6

[Nicolas Chevobbe [:nchevobbe]]

Attachment: Bug 1473473 - Expose isClassConstructor in Debugger.Object. r=loganfsmyth.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/68ab3d76c355
Expose isClassConstructor in Debugger.Object. r=loganfsmyth.

Comment 8

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/mozilla-central/rev/68ab3d76c355

Comment 9

[Arthur Iakab [arthur_iakab]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/68ab3d76c355