Building contracts manually

cargo odra is a great tool to build and test your contracts, but sometimes a better control over the parameters that are passed to the cargo or the compiler is needed.

This is especially useful when the project has multiple features, and there is a need to switch between them during the building and testing.

Knowing that cargo odra is a simple wrapper around cargo, it is easy to replicate the same behavior by using cargo directly.

Building the contract manually

To build the contract manually, cargo odra uses the following command:

ODRA_MODULE=my_contract cargo build --release --target wasm32-unknown-unknown --bin my_project_build_contract

info

Odra uses the environment variable ODRA_MODULE to determine which contract to build.

Assuming that project's crate is named my_project, this command will build the my_contract contract in release mode and generate the wasm file. The file will be put into the target/wasm32-unknown-unknown/release directory under the name my_project_build_contract.wasm.

The Odra Framework expects the contracts to be placed in the wasm directory, and to be named correctly, so the next step would be to move the file:

mv target/wasm32-unknown-unknown/release/my_project_build_contract.wasm wasm/my_contract.wasm

Optimizing the contract

First, cargo odra runs the wasm-opt tool:

wasm-opt --signext-lowering wasm/my_contract.wasm -o wasm/my_contract.wasm

Then it lowers the size of the wasm file with the wasm-strip tool:

wasm-strip wasm/my_contract.wasm

caution

The order matters. wasm-strip removes the sections wasm-opt needs to validate the module, so running it first makes wasm-opt fail with thousands of validation errors.

warning

This step is required, as the wasm file generated by the Rust compiler is not fully compatible with the Casper execution engine.

Running the tests manually

To run the tests manually, Odra needs to know which backend to use. To run tests against Casper backend, the following command needs to be used:

ODRA_BACKEND=casper cargo test

Wrapping up

Let's say we want to build the my_contract in debug mode, run the tests against the casper backend and use the my-own-allocator feature from our my_project project.

To do that, we can use the following set of commands:

ODRA_MODULE=my_contract cargo build --target wasm32-unknown-unknown --bin my_project_build_contract
mv target/wasm32-unknown-unknown/debug/my_project_build_contract.wasm wasm/my_contract.wasm
wasm-opt --signext-lowering wasm/my_contract.wasm -o wasm/my_contract.wasm
wasm-strip wasm/my_contract.wasm
ODRA_BACKEND=casper cargo test --features my-own-allocator