Combining branch data on parallel runs?

[mjankowski]

I'm attempting to setup a simplecov<>flatware integration on a fairly standard rspec suite. I've got the basic config working, and I can get the normal line coverage results to merge correctly (using LCOV formatter if that matters), but the branch data coverage seems to get dropped when run via the parallel/flatware runner, while it's present when run via the normal non parallel rspec runner.

I see some open PRs/issues (#972 #1084 #1081) related to branch data, so maybe this a known issue...?

Any pointers appreciated, happy to provide more info. Current efforts captured in mastodon/mastodon#30284 (comment)