Vyper support is limited

[ggrieco-tob]

Echidna works on vyper contracts running the .vy files directly, however:

• properties should be hardcoded in the contract
• any use of framework will fail to work (e.g. brownie).
• slither won't run on it, so there is no constant extraction or assertion detection.
• we still get the constants if they are returned by a function inside the code
• coverage feedback and source code integration works

It is expected to have a limited effectiveness since we cannot get useful constants from the source code.

[ggrieco-tob]

This is something we won't fix unless Vyper has more traction.

[pcaversaccio]

FYI, I added Echidna to my 🐍 snekmate Vyper contracts: pcaversaccio/snekmate#239. Some important learnings:

• hevm doesn't strip whitespace characters (!) when FFI is used,
• use filterFunctions in the Echidna config file to remove crashing calls to the VyperDeployer contract if allContracts: true is used.