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 (opens in a new tab).

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:

TERMINAL

rustup target add wasm32-unknown-unknown

The cosmwasm-check utility

An additional helpful tool for building smart contracts is the cosmwasm-check (opens in a new tab) 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:

TERMINAL

cargo install cosmwasm-check

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

TERMINAL

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 (opens in a new tab) repository and run the testing command in its folder:

TERMINAL

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 (opens in a new tab) 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 (opens in a new tab) utility, first, you need to build a smart contract. Go to some contract directory, for example, contracts/cw1-whitelist, and call cargo wasm:

TERMINAL

cd contracts/cw1-whitelist && cargo wasm

💡

Due to reference types feature enabled by default in the Rust compiler since version 1.82 it is required to use the previous Rust compiler releases until the CosmWasm 2.2 version is released. The CosmWasm 2.2 will enable support for the reference types.

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:

TERMINAL

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!

Tutorial CosmWasm Contract