8 releases

0.1.1 Nov 21, 2022
0.1.0 Nov 17, 2022
0.0.5 May 18, 2022

#52 in #wit

23 downloads per month

MIT and LGPL-3.0-or-later

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Just raen build to add fully-typed, discoverable interfaces to your smart contracts.

RAEN Admin and New Tools Coming Soon can use these interfaces to make life easier.

Without RAEN, there's no easy way for smart contract authors or the people building apps on top of their contracts to know what methods a smart contract has, or what arguments they take. Ethereum solves this with ABIs, JSON files that contract authors need to distribute off-chain to app-builders or documentation-maintainers who want to integrate with or describe the contract. Pagoda fka Near Inc is working on a clone of Ethereum's approach.

RAEN leap-frogs this approach. It uses a Wasm-compatible standard that is more compact than JSON, can be auto-translated to Pagoda's ABI or other formats like OpenRPC, and will one day merge with Wasm core. And RAEN injects Wit directly into the smart contract while reducing overall contract size. No more searching GitHub for ABI files. Now they can all live right on-chain.

In a RAEN-maximized version of NEAR, anyone will be able to easily generate cross-contract call logic, TypeScript libraries, CLIs, Admin UIs / interactive documentation, Subgraphs and more, just using a contract name.

The best part? Getting started couldn't be easier. It's one command. Just build your contracts with raen build.

Rust-only, for now. New to Rust or NEAR? Check out The RAEN Guide.


About the name

"RAEN" is "NEAR" spelled backwards. It is pronounced the same as "rain".


New to Rust? Step-by-step instructions on the Guide.


raen is a Rust crate and can be installed via cargo:

cargo install raen

If you don't yet have Rust, you will need to install it before running the above command. On Linux or MacOS, use the following command:

curl --proto '=https' --tlsv1.2 https://sh.rustup.rs -sSf | sh

source $HOME/.cargo/env

Then, add the wasm32-unknown-unknown toolchain. This toolchain is required because NEAR contracts need to be compiled to [Wasm] with architecture and platform both "unknown".

rustup target add wasm32-unknown-unknown

Then follow these instructions for setting up Rust.

npm (optionally)

raen is also distributed on npm which wraps the rust binary built for your computer:

npm install --global raen-cli

Additional requirements

raen is designed as an extension for near-cli-rs, but until this project is stable you need to install the JS version near-cli to deploy your contracts.

npm install --global near-cli


For an intro to NEAR, Rust, and RAEN, see ✨ The Guide ✨. The basics:

In a NEAR smart contract project:

raen build --release

This builds the contract (or contracts if you're using a Rust workspace), embeds the contract's types in a Custom Section, and places them in ./target/res/crate_name.wasm.

You can then deploy as usual with near-cli. With dev-deploy:

near dev-deploy --wasmFile ./target/res/crate_name.wasm

With deploy:

near deploy --wasmFile ./target/res/crate_name.wasm --accountId YOUR_ACCOUNT_NAME_HERE

Various current and future tooling can now use your contract's types to make your life easier. For example, you can enter your contract's address at raen.dev/admin for a full admin panel.

Learn: How it works: Wasm 💖️ Wit

[Wit] is an emerging standard to ease interoperability between programs compiled to WebAssembly, aka [Wasm]. (Wit stands for "WebAssembly Interface Types.") Wit will eventually merge with Wasm, allowing all compiled Wasm modules to explain their interfaces to other Wasm modules and their developers.

NEAR runs Wasm. Any Wasm language, though Rust has the most mature tooling and documentation.

When you build your smart contracts with raen, it injects a full Wit specification for your contract into a Wasm Custom Section. It compresses it with brotli to reduce storage requirements.

How much does this increase your contract size? In our tests so far, contracts compiled with raen end up smaller than before!

raen uses witme to generate the Wit and inject it into the Wasm Custom Section. Under the hood, witme uses walrus, which optimizes the Wasm enough to reduce the total contract size, even with the Wit. We will add full benchmarks soon.

(Note that currently a JSON AJV specification is added to a Wasm Custom Section instead of Wit, since 1. No Wit-to-AJV tooling currently exists for browsers, 2. This admin panel relies on AJV, and 3. No other tooling currently makes use of Wit. The AJV custom section will be swapped for a Wit custom section once Wit settles on an initial syntax version.)

This admin panel then reads in that Custom Section, decompresses the brotli, and uses react-jsonschema-form to allow interacting with the contract.


witgen macro

If you define a type that RAEN doesn't recognize (such as in this line type Amount = Balance; where RAEN doesn't recognize Amount), your build may result in an error like:

You probably need to add a `witgen` macro to the missing type

Add 'witgen' as a dependency to add to type definition. e.g.

Error: no type named `amount`

// Or 
You probably need to add a `witgen` macro to the missing type

Add 'witgen' as a dependency to add to type definition. e.g.

   1 use witgen::witgen;
   3 /// Type exposed by contract API
   4 #[witgen]
   5 struct Foo {}
Error: no type named `amount`
     --> index.ts:9:73
    9 | transfer-from-escrow: function(destination-account: account-id, amount: amount)
      |                                                                         ^-----

To fix this:

  1. You might want to run cargo add witgen (which will edit your Cargo.toml to include a line like witgen = "0.14.0").
  2. Add use witgen::witgen; near the top of the file that was causing the error.
  3. Add #[witgen] as a line before the definition of the type. E.g.:
use witgen::witgen;

type Amount = Balance;


Now including the following in your Cargo.toml will allow projects to include your wit types in their generated wit.

export = true


  • Clone this repository
  • Build with cargo build
  • Send us issues or pull requests with questions and we'll improve this section!


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