Fix hardhat_reset (#667) and add unit tests

[cgewecke]

Co-authored-by: Andres Adjimann [email protected]

Have written a test for #667 but it fails. My expectation is that given a contract with 2 simple functions I can:

• call function 1
• hardhat_reset
• call function 2

... and have 100% line coverage. Instead I see this:

In the hardhat code it looks like the hardhat node is destroyed and recreated on each reset event. For solidity-coverage to re-attach a step listener to its vm it's important that we get a reference to the new node object. Have found this to be impossible so far.

Event listeners attached to the new (or is it old for some reason?) vm never fire.

Note: I've slightly modified the logic in the new PR to use an env scoped reference to the network provider but the incorrect behavior exists for #667's approach as well. Have also tried:

• using setTimeout in various places to make sure I'm not running into an event related race condition.
• re-running nomiclabsUtils.setupHardhatNetwork(env, api, ui) in the reset event call back
  • interestingly, during the attachment sequence this discovered a root provider object with no hardhat node object. It's possible we may not be able to get a new reference to the node because of the way the provider object is proxied on reset in hardhat-ethers

[codecov-commenter]

Codecov Report

Merging #681 (a0cc952) into master (cdab28c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #681   +/-   ##
=======================================
  Coverage   98.69%   98.69%           
=======================================
  Files          22       22           
  Lines         993      996    +3     
=======================================
+ Hits          980      983    +3     
  Misses         13       13           

Impacted Files	Coverage Δ
plugins/hardhat.plugin.js	93.68% <100.00%> (+0.20%)	⬆️

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[jummy123]

Thank you for your work on this fix ❤️