The original article appeared in the Stylus Saturdays blog

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How to verify your Stylus contracts using the Blockscout’s API

We support verifying Stylus contracts located in public GitHub repositories. The swagger file for our API endpoint to request the verification can be found here. The endpoint accepts the following fields: deployment_transaction, rpc_endpoint, cargo_stylus_version, repository_url, commit, and path_prefix The path_prefix is required so that repositories with several contract crates inside can be used. The repository https://github.com/blockscout/cargo-stylus-test-examples contains some great examples. When a user visits the verification UI, they provide the cargo_stylus_version, repository_url, commit, and path_prefix values. These values, along with the address of the contract being verified, are sent to an Elixir backend. The backend retrieves the deployment_transaction from the internal database, and sends the data it collected so far, and the rpc_endpoint, to a separate verification service. The service validates the repository, clones the repo the user provided, and checks out the commit hash. If path_prefix is provided, it enters the corresponding prefix, which is calculated relative to the repository root directory. Stylus requires the Rust toolchain version to be specified in a rust-toolchain.toml file. The file has to be located inside the working directory. For verification, Blockscout uses the command cargo stylus verify --no-verify --endpoint {rpc_endpoint} --deployment-tx {deployment_transaction}`. We opt out of running verification inside in-stylus docker container by adding the --no-verify flag. We opt out because cargo-stylus requires the docker daemon to be run locally, but we would like to run the service and docker daemon on different machines. We implemented our own docker container startup process which allows us to run containers on the remote docker daemon. cargo stylus verify prints the result into console. We parse the stdout and look for the line: “Verified - contract matches local project's file hashes”. If found, the verification is considered successful, otherwise the verification fails. If successful, we also attempt to retrieve the contract ABI as it is not returned by the verify command. To get the abi, we run the cargo stylus export-abi command, and parse its result. It prints the ABIs of all included contracts, and the verified contract ABI is printed as the last one. The name of this ABI is also used as a contract name inside a response. If you need the code, the main function is implemented here: https://github.com/blockscout/blockscout-rs/blob/main/stylus-verifier/stylus-verifier-logic/src/stylus_sdk_rs.rs#L76 An example of making a request to the Blockscout API for verification: 
curl 'https://arbitrum.blockscout.com/api/v2/smart-contracts/<address_hash>/verification/via/stylus-github-repository' -H 'Content-type: application/json' -d '{"cargo_stylus_version":"v0.5.6","repository_url":"https://github.com/OffchainLabs/stylus-erc20","commit":"d109002ffff3df7589cbbc92f8f104567a84f085","path_prefix":"","license_type":"none"}'