Environment setup

Rust installation

To work with CosmWasm smart contract, you will need Rust installed on your machine. If you don’t have it, you can find installation instructions on the Rust website.

I assume you are working with the stable Rust channel in this book.

Additionally, you will need the Wasm rust compiler backend installed to build Wasm binaries. To install it, run:

rustup target add wasm32-unknown-unknown

The cosmwasm-check utility

An additional helpful tool for building smart contracts is the cosmwasm-check utility. It allows you to check if the wasm binary is a proper smart contract ready to upload into the blockchain. You can install it using cargo:

cargo install cosmwasm-check

If the installation succeeds, you should be able to execute the utility from your command line.

cosmwasm-check --version

The output should look like this:

Contract checking 1.2.3

Verifying the installation

To guarantee you are ready to build your smart contracts, you need to make sure you can build examples. Check out the cw-plus repository and run the testing command in its folder:

git clone git@github.com:CosmWasm/cw-plus.git && cd ./cw-plus && cargo test

You should see that everything in the repository gets compiled and all tests pass.

The cw-plus is a great place to find example contracts - look for them in the contracts directory. The repository is maintained by CosmWasm creators, so contracts in there should follow good practices.

To verify the cosmwasm-check utility, first, you need to build a smart contract. Go to some contract directory, for example, contracts/cw1-whitelist, and call cargo wasm:

cd contracts/cw1-whitelist && cargo wasm

You should be able to find your output binary in the target/wasm32-unknown-unknown/release/ of the root repo directory - not in the contract directory itself! Now you can check if contract validation passes:

cosmwasm-check ../../target/wasm32-unknown-unknown/release/

cw-plus/contracts/cw1-whitelist $ cosmwasm-check
../../target/wasm32-unknown-unknown/release/cw1_whitelist.wasm Available capabilities: {"iterator",
"cosmwasm_1_1", "cosmwasm_1_2", "stargate", "staking"}
 
../../target/wasm32-unknown-unknown/release/cw1_whitelist.wasm: pass
 
All contracts (1) passed checks!

Macro expansion

In VSCode you can hover over a macro like #[contract], do shift+p and then type: rust analyzer: Expand macro recursively. This will open a window with a fully expanded macro, which you can browse. In Vim you can consider installing the rustaceanvim plugin. You can also use cargo expand tool from CLI, like this:

cargo expand --lib