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hackbg / chainlink-terra-cosmwasm-contracts

Chainlink Protocol implementation in CosmWasm (Rust) for Terra blockchain
Apache License 2.0
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chainlink terra

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Chainlink Terra

Developing

Prerequisites

Before starting, make sure you have rustup along with a recent rustc and cargo version installed (1.44.1+).

rustc --version
cargo --version
rustup target list --installed

And you need to have the wasm32-unknown-unknown target installed as well. In case it is missing.

rustup target add wasm32-unknown-unknown

Compiling and running tests

Now that you created your custom contract, make sure you can compile and run it before making any changes. Go into the repository and do:

# this will produce a wasm build in ./target/wasm32-unknown-unknown/release/YOUR_NAME_HERE.wasm for every contract
cargo wasm

# this runs unit tests with helpful backtraces
RUST_BACKTRACE=1 cargo unit-test

# You can also run these commands only for a specific contract. E.g.
cargo wasm -p chainlink-client

Understanding the tests

The main code for each contract is in src/contract.rs and the unit tests there run in pure rust, which makes them very quick to execute and give nice output on failures, especially if you do RUST_BACKTRACE=1 cargo unit-test.

We consider testing critical for anything on a blockchain, and recommend to always keep the tests up to date.

Generating JSON Schema

While the Wasm calls (init, handle, query) accept JSON, this is not enough information to use it. We need to expose the schema for the expected messages to the clients. You can generate this schema by calling cargo schema, which will output 4 files in ./YOUR_CONTRACT/schema, corresponding to the 3 message types the contract accepts, as well as the internal State.

# auto-generate json schema

cd ./contracts/YOUR_CONTRACT
cargo schema

These files are in standard json-schema format, which should be usable by various client side tools, either to auto-generate codecs, or just to validate incoming json wrt. the defined schema.

Preparing the Wasm bytecode for production

Before we upload it to a chain, we need to ensure the smallest output size possible, as this will be included in the body of a transaction. We also want to have a reproducible build process, so third parties can verify that the uploaded Wasm code did indeed come from the claimed rust code.

To solve both these issues, we are using rust-optimizer (or to be specific in our case - workspace-optimizer), a docker image to produce an extremely small build output in a consistent manner. The suggested way to run it is this:

docker run --rm -v "$(pwd)":/code \
  --mount type=volume,source="$(basename "$(pwd)")_cache",target=/code/target \
  --mount type=volume,source=registry_cache,target=/usr/local/cargo/registry \
  cosmwasm/workspace-optimizer:0.11.4

Or using the script that does the same:

./script/optimize.sh

We must mount the contract code to /code. You can use a absolute path instead of $(pwd) if you don't want to cd to the directory first. The other two volumes are nice for speedup. Mounting /code/target in particular is useful to avoid docker overwriting your local dev files with root permissions. Note the /code/target cache is unique for each contract being compiled to limit interference, while the registry cache is global.

This is rather slow compared to local compilations, especially the first compile of a given contract. The use of the two volume caches is very useful to speed up following compiles of the same contract.

This produces an artifacts directory in the root of the workspace. It contains the compiled and optimized WebAssembly output of the contracts along with a Sha256 checksum in hash.txt.

Testing production build

Once we have this compressed contract.wasm, we may want to ensure it is actually doing everything it is supposed to (as it is about 4% of the original size). If you update the "WASM" line in tests/integration.rs, it will run the integration steps on the optimized build, not just the normal build. I have never seen a different behavior, but it is nice to verify sometimes.

static WASM: &[u8] = include_bytes!("../contract.wasm");

Note that this is the same (deterministic) code you will be uploading to a blockchain to test it out, as we need to shrink the size and produce a clear mapping from wasm hash back to the source code.

Contributing

For commit message naming convention we use conventional commits. While this is not enforced, please try to stick to this as it eases the reviewers and also allows us to build automated changelog directly out of the commit messages if compliant to the format.

We use the gitflow workflow this is also helpful.

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