Palemoon refuses to prettify JS source code if source maps are disabled

[mmouse]

Operating system: Linux (Kubuntu)
Browser version: 33.7.2
32-bit or 64-bit browser?: 64 bit
Problem URL: not specific
Browser theme (if not default):
Installed add-ons: repro with all add-ons disabled
Installed plugins: (about:plugins): none

Problem: when trying to prettify JS source code, a wait popup is displayed for a few seconds then nothing happens: the JS code stays not prettifyed.

Cause: pref devtools.debugger.source-maps-enabled is set to false (default to true)

Now this is making a bit of evil sense, but there is really no reason to check for source maps if the action happens entirely without touching any source map (as these source maps are lacking for most web pages found on the Internet).

Even if there is a good reason to not pretty JS source code if source maps are disabled, an appropriate answer should rather be to display somewhere a message saying what is the problem, and definitely not to actually do the work (debugging the thing makes clear that when the wait popup is displayed the web thread is really producting a pretty JS code and it is entirely correct), while refusing to set it in the debug window, without any notice that something is wrong.

By the way, I don't think now that this feature has any relation to a particular system and think rather that it would probably appear under Windows.

Looking at source history, it seems that this option is not coming from Firefox, it was added in the Palemoon source code. Well, why was it done this way ?

[Moonchild]

Looking at source history, it seems that this option is not coming from Firefox, it was added in the Palemoon source code.

You're mistaken. This was introduced as a preference in the UXP source with its first commit, so it most definitely came from Firefox.

As for the mechanics of this interaction... Nobody has touched that code (devtools are mostly provided as-is from the Mozilla source) but it does make perfect sense that it relies on this plumbing. Prettifying rewrites source files in a very similar way source maps would, so I assume it wants to use the same plumbing, which that pref probably disables.
Note: I didn't look into the code, this is just an educated guess. it could also be a bug, but I can't tell from where I'm sitting at the moment.

[mmouse]

With the first commit ? I looked at it and there was not much use of this option; however it was indeed fleshed out in the ESR 52 commit next day .

I did not find any reference to this option in Firefox source code either, but looking harder, I think I understand why: it seems that Firefox has cut on history in main branch, maybe to make git history less crushing, main branch begins in 2018; however by switching to the oldest ESR in Firefox, 125, whose history begins in 2015, I can find it, and it seems to have been removed in 21369e75a2b60d6d808d531c02101e7b2359aeae - linked to bug

https://bugzilla.mozilla.org/show_bug.cgi?id=1513655

removing source map server handling in Firefox 66 (that is, far after the Palemoon cut-off) because of the 'new Html debugger' replacing it, so I guess that if there was a bug it will not be of concern to Firefox anymore.

[Moonchild]

With the first commit ? I looked at it and there was not much use of this option; however it was indeed fleshed out in the ESR 52 commit next day .

With the first UXP commit of substance, yes. When the FF 52.6.0 source was imported.

(noticed I highlighted the wrong pref. but you get my drift, I hope)