Allow 1 count block request to return 0 blocks

[dapplion]

Issue Addressed

Noted the following bug in ReqResp logic:

• We issue a ReqResp request for blocks where the count of requested elements is 1
• The peer does not have the requested element and returns 0 elements
• We consider that a protocol violation with RPCError::IncompleteStream

Not having a block or blob is tolerated as per the req resp spec. It's the downstream caller that should decide if the peer should have or not that specific element.

Proposed Changes

Rename expected_responses to max_responses, as for multiple responses that what the number really represents. The peer is allow to return less than the request count of elements, including 0.

Add a new function expect_exactly_one_response to differentiate those request where closing the stream before the first element is actually a protocol violation (e.g. status method)

I have reversed some of the if else cases, (from if !condition A else B to if condition B else A, but the actual logic is unchanged.

Additional Info

Please provide any additional information. For example, future considerations
or information useful for reviewers.

[pawanjay176]

Nice catch. LGTM

[realbigsean]

@Mergifyio queue

[mergify]

queue

✅ The pull request has been merged automatically

The pull request has been merged automatically at 5fdd3b3