Is there a use-case for running any other version of flash, than adobe's latest? If not, I'd rather not build an escape hatch here, but have flashplayer kept up to date in supported releases.

I think a better approach would be to join npapi - flashplayer (from mozilla) and ppapi - flashplayer (from chromium) into a single top-level derivation:

• This would join forces to keep flashplayer updated
• Overriding the version (like in this PR) could then be done by package overrides

@bendlas I don't have a use-case for anything but latest Flash (although, heaven's defend them, someone might e.g. for development). But Adobe releases new versions (and yanks the immediately previous one) on their own schedule, which means that until there is an override somewhere, nixpkgs will be able to install Flash only some of the time.

As to joining them into a single derivation - how would that work? The two plugins come from different sources and have different hashes.

Moving the ppapi one to a simple top-level derivation, however, makes complete sense to me. Should we do that?

I don't have a use-case for anything but latest Flash (although, heaven's defend them, someone might e.g. for development).

That's my point exactly. If you were to update your own flashplayer, it should be done in a way that your whole system profits, not just chromium. Hence, the flash should go through pkgs, so that it can be updated via regular packageOverride.

As to joining them into a single derivation - how would that work?

I'm envisioning a single version attribute, that would control both npapi and ppapi flash, since, as you say, both versions are simultaneously released by adobe. Two separate hashes, yes. Ideally, it would come with an update script, writing version info to a json file, and/or be able to be updated by bot.
That said, it should still be two separate derviations (since FF doesn't care about ppapi and vice versa), but we should maximise the chances of somebody updating npapi also updating ppapi.

Moving the ppapi one to a simple top-level derivation, however, makes complete sense to me. Should we do that?

I'd say: go for it. We can still do something about npapi later.

Thank you for your contributions.
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This is still important to me, I would prefer that some kind of flashplayer cache be added or used but in lieu of that having the version exposed would help greatly.

flashplayer is deprecated.