fix(share/getters): short-circuit on empty root in ShrexGetter

[distractedm1nd]

Should fix issue where GetEDS hangs on empty data root

To test run:

celestia share get-eds “$(celestia header get-by-height 500 --node.store ~/.celestia-light-mocha-4 | jq .result)” --node.store ~/.celestia-light-mocha-4

with and without the PR

[Wondertan]

So I tested this on LN, and I never triggered hitting. I found though a weird behaviour. It's guaranteed that LN gets an empty block on the first time with slight delay, but it always stuck on the further tries.

[Wondertan]

Note, we need to add empty block test case to our Getter test suite

[distractedm1nd]

Hmm, a swamp test of a LN calling twice resolves both times and logs hitting - I wonder what is different between swamp and the real call. Are you sure the node was running the right build?

[Wondertan]

I'lol double check tmrw @distractedm1nd

[distractedm1nd]

It is logging hit for me every time, and doesn't hang ever even on multiple runs 🤔

But on main, it retrieves after the first time, logging

2023-10-16T14:05:26.436+0200	ERROR	header/p2p	p2p/exchange.go:166	verifying head received from tracked peer	{"tracked peer": "12D3KooWS7CW7y1VRuHif4nJqLyUyUtHaCFmJDEfTd9wMpgFucNk", "height": 290816, "err": "header verification failed: known header: '290816' <= current '290816'"}
2023-10-16T14:05:26.437+0200	ERROR	header/p2p	p2p/exchange.go:166	verifying head received from tracked peer	{"tracked peer": "12D3KooWHHUVwvXgdxg4k2GtfSA6yB6iDJ1fBYnvBU9LhSMzoi2A", "height": 290816, "err": "header verification failed: known header: '290816' <= current '290816'"}
2023-10-16T14:05:26.842+0200	ERROR	header/p2p	p2p/exchange.go:166	verifying head received from tracked peer	{"tracked peer": "12D3KooWQNp5N12C19cDvhDSAVLnW6tYjthZs1abi3mpXpSqwkpJ", "height": 290816, "err": "header verification failed: known header: '290816' <= current '290816'"}
2023-10-16T14:05:26.853+0200	ERROR	header/p2p	p2p/exchange.go:166	verifying head received from tracked peer	{"tracked peer": "12D3KooWHEU9efXKk5PeCyWyNVz2YYwW8bzxv25vjtfiJN6fLpTE", "height": 290816, "err": "header verification failed: known header: '290816' <= current '290816'"}

And then fails the second time.

So confirmed that this is fixing the issue

[codecov-commenter]

Codecov Report

Merging #2846 (617f823) into main (a52e2de) will increase coverage by 0.15%.
Report is 5 commits behind head on main.
The diff coverage is 25.00%.

@@            Coverage Diff             @@
##             main    #2846      +/-   ##
==========================================
+ Coverage   51.30%   51.46%   +0.15%     
==========================================
  Files         168      167       -1     
  Lines       10744    10773      +29     
==========================================
+ Hits         5512     5544      +32     
+ Misses       4750     4727      -23     
- Partials      482      502      +20     

Files	Coverage Δ
share/getters/shrex.go	65.55% <25.00%> (-0.93%)	⬇️

... and 16 files with indirect coverage changes