The Touch Device mod is hidden from replays

[ZenoG2]

Type

Cosmetic

Bug description

Touch devices are not signaled correctly.

Screenshots or videos

Version

2024.906.2-lazer

Logs

compressed-logs.zip

[bdach]

So I presume this is happening if the user starts the play using mouse but then starts touching midway through the game because this 100% impacts only some replays. The fact of starting the touching is not conveyed to osu-server-spectator, which is responsible for recording replays, and thus is blissfully unaware of this; submission happens at the end of the score, with TD successfully present, but web will serve the replay recorded by osu-server-spectator raw which means that the information about TD is dropped from the replay.

The two obvious fixes are to either:

• have osu-server-spectator know that mods changed (probably by sending them in the frame bundles - possibly wasteful if not done with a bit of deduplication to only send changes),
• have osu-web correct the replay in post when serving it, similarly to how I believe it currently manufactures the replay headers for stable replays?

@ppy/team-client opinions?