Clarify BeaconBlockAndBlobsSidecarByRoot no blob available

[dapplion]

Peers may not know the slot of a block when requesting by root. So they may request a root via BeaconBlockAndBlobsSidecarByRoot which does not have any associated blob.

• Details of the edge case: EIP-4844: blobs / blocks by root edge case #3113

This situation only applies before finalizing EIP4844_FORK_EPOCH. From discussions in #3139 a simple solution that requires a retry is the best trade-off to minimize complexity.

I picked the error code 3: ResourceUnavailable without strong reasoning. Happy to change to another more meaningful one.

[djrtwo]

nice!

[dapplion]

@djrtwo thanks for the feedback, applied comments. Should there be a sentence noting the consequences of that line if finalized_epoch < current_epoch - MIN_EPOCHS_FOR_BLOBS_SIDECARS_REQUESTS?

• Related to Consider old finalized data available? #3141

[djrtwo]

@dapplion Is that because you don't think the max is clear enough and want to make sure it's called out explictly? or something else

[dapplion]

Wording is clear to us, but the consequences as discussed today are important. So I feel that (for new readers for example) calling out that nuance is a useful pointer

[djrtwo]

I'm fine with an explicit line @dapplion but also happy to merge as is

[g11tech]

Lgtm

[djrtwo]

merging! feel free to add an additional comment in another PR

[ghost]

😱...estoy atónito!!!!