I have been chasing a runaway Electron disk cache on my Mirror (Pi 5, MM 2.34.0) and added what I thought was the obvious fix to my config.js:

electronSwitches: ["disk-cache-size", "104857600"],   // 100 MB

Some months later the cache had grown to 2 GB (260,000+ files in ~/.config/Electron/Cache/Cache_Data/).
My limit appeared to be ignored entirely.

When I looked at js/electron.js line 47 I think I see why, but I want to sanity-check this with the community — maybe I am simply misreading the code.

The line is:

app.commandLine.appendSwitch(...new Set(electronSwitchesDefaults, config.electronSwitches));

As far as I understand it, two things are happening here:

1. new Set(a, b) silently drops the second argument.

The Set constructor signature is new Set([iterable]) — it accepts exactly one iterable. Any further arguments are ignored. So I believe this is equivalent to:

new Set(electronSwitchesDefaults)

and config.electronSwitches never makes it in.
Is that right?
Or am I missing some clever JavaScript I have not seen before?

2. appendSwitch only takes one switch per call.

The Electron docs state the signature is appendSwitch(switch, value?). Spreading a flat array of multiple switches into a single call should — if I understand correctly — only honour the first switch/value pair and silently discard the rest.

The defaults array ([“autoplay-policy”, “no-user-gesture-required”]) happens to be exactly one switch with one value, so that one works. But anything a user adds via config.electronSwitches would never take effect, even if point 1 were fixed.

If both readings are correct, the natural fix would be a loop, something like:

const switches = [["autoplay-policy", "no-user-gesture-required"], ...(config.electronSwitches || [])];
switches.forEach(([s, v]) => app.commandLine.appendSwitch(s, v));

or, if electronSwitches is documented as a flat array, the user-facing schema would need to be specified more clearly first.

My questions to the forum:

• Is my reading of new Set(a, b) correct here?
• Has anyone successfully used electronSwitches to actually change Electron behaviour, and if so, with what syntax?
• Is this maybe legacy code that the community has worked around in other ways I am not aware of?

Thanks,
Ralf