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v0.1.2 predates the crate rename (fai-module-sdk) and the WIT 1.1 Context::emit addition; the chain CLI's module scaffold now pins a tag instead of branch=main, so module builds stay reproducible. Example lockfile catches up with the rename. Signed-off-by: flemming-it <sf@flemming.it> |
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| .forgejo/workflows | ||
| crates | ||
| examples | ||
| wit | ||
| .gitignore | ||
| Cargo.lock | ||
| Cargo.toml | ||
| LICENSE | ||
| NOTICE | ||
| README.md | ||
| rust-toolchain.toml | ||
chain-module-sdk
Stable, ergonomic Rust surface for writing Ch∆In modules.
A module written against this crate looks like:
use chain_module_sdk::prelude::*;
#[fai_module]
fn invoke(_ctx: Context, inputs: Inputs) -> Result<Outputs, ModuleError> {
let text = inputs.require_text("input")?;
Ok(Outputs::new().with_text("output", format!("echo: {text}")))
}
That single function — plus a Cargo.toml listing
chain-module-sdk as a dependency — is the entire module. The
#[fai_module] macro generates the wit_bindgen invocation, the
Guest implementation, the type conversions, and the
wit_bindgen::export! glue behind the scenes.
What the SDK gives you
| You get | Instead of |
|---|---|
Inputs::require_text("name") |
manual match payload { Payload::Text(s) => ..., _ => ... } |
Outputs::new().with_json(...)? |
building Vec<(String, Payload)> by hand |
ModuleError::invalid_input("...") |
constructing WIT invocation-error variants |
ctx.emit("progress", ...) |
hand-rolling the host.emit-event import (WIT 1.1) |
#[fai_module] |
wit_bindgen::generate! + Guest impl + export! + #![allow(unsafe_op_in_unsafe_fn)] |
Stability
The SDK insulates module code from the underlying WIT contract
(chain:platform, currently v1.1 — frozen base v1.0 plus the
additive 1.1 emit-event import). The WIT may evolve in
additive minor versions or, eventually, a coordinated v2.0; the
SDK absorbs that change so existing module code keeps compiling.
The SDK ships its own copy of wit/world.wit so that the
proc-macro can embed the contract via include_str! at compile
time. A snapshot test (crates/chain-module-sdk/tests/wit_freeze.rs)
asserts the SHA-256 matches the platform's frozen hash — if the
two ever drift, CI fails.
Versioning
| Track | Stability |
|---|---|
WIT contract (chain:platform) |
v1.1; base frozen at v1.0, minors are additive |
chain-module-sdk Rust API |
Semver; v0.x while ergonomics evolve |
| Per-module versions | Each module repo's own concern |
License
Apache-2.0. See LICENSE.
Author: Dr. Stefan Flemming, Flemming.AI chain@flemming.ai Repository: https://git.flemming.ai/fai/chain-module-sdk-rust