Current interop issue: some browsers use displayName property

[domenic]

They should only be using name these days, but some still keep it around. Would be good to standardize on this being disallowed and write tests as such.

[ljharb]

@domenic sorry for the delay here; can you elaborate on exactly how (and which) some browsers use this property?

[domenic]

Some browsers use the displayName property of a function, instead of using the function's name property, in stack traces.

As for exactly which, I have the time to raise a known issue for the proposal champions, but not to do the research required to drive the proposal, since I am not a champion myself.

[ljharb]

Thanks; looks like Safari, at least, shows g with:

function f() { return new Error(); }
f.displayName = 'g';
f().stack;

Chrome and Firefox and IE 11 and Edge do not.

cc @msaboff @kmiller68 @erights

[loganfsmyth]

For Firefox/SpiderMonkey, there's also reason to clearly define expectations here because when there is no "name" for a function, SpiderMonkey currently attempts to provide a useful description of where the anonymous function is declared, for example:

function parent() {
  return (() => {
    return new Error().stack;
  })();
}
parent();

results in

parent/<@debugger eval code:3:12
parent@debugger eval code:4:5
@debugger eval code:6:1

with parent/< representing "an anonymous function defined inside 'parent'". There's also other cases like

function parent() {
  return {
    prop: (() => {
      return new Error().stack;
    })()
  }.prop;
}
parent();

which output

parent/<.prop<@debugger eval code:4:14
parent@debugger eval code:5:7
@debugger eval code:8:1