libflux/composite_future: propagate child errors to parent #2099
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This is something I ran across in the
job-exec
module, when buildingflux_future_and_then
chains of composite futures.Currently, composite "wait all" and "wait any" futures are fulfilled with success as soon as all or any of their child futures are fulfilled, whether with success or failure. This makes it challenging to use
and_then
chains, which are supposed to break immediately (propagate the error) when an intermediate future is fulfilled with error.This PR just sets up the check for composite future fulfillment to propagate any error from the children to the "parent". To see the exact error or more detail, the user should still iterate over child futures (e.g. to see which future or futures were fulfilled with error)