fix: ensure subgraphNFT handles metadata with leading zeros correctly

[tmigone]

Motivation

The tokenURI being reported by SubgraphNFT contract using the tokenURI function is incorrect when the subgraph metadata hash contains leading zeroes. #576 describes the problem in detail.

Changes

• Added test to check for this special case where subgraph metadata hash is of the form 0x00....
• Fix in SubgraphNFT contract

Closes: #576
Signed-off-by: Tomás Migone tomas@edgeandnode.com

[codecov]

Codecov Report

Merging #577 (ff7880e) into dev (6e9b7f1) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##              dev     #577   +/-   ##
=======================================
  Coverage   90.49%   90.49%           
=======================================
  Files          35       35           
  Lines        1747     1747           
  Branches      290      290           
=======================================
  Hits         1581     1581           
  Misses        166      166           

Flag	Coverage Δ
unittests	90.49% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
contracts/discovery/SubgraphNFT.sol	100.00% <100.00%> (ø)

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[pcarranzav]

Since we won't be able to deploy this fix, should we close this and leave the issue open as a known bug? (We can reopen if we ever get a chance to deploy a new SubgraphNFT for whatever reason)