flemming-it
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The public macro name was the last product-scoped 'fai' identifier in the SDK surface. #[chain_module] is now the primary attribute (README + examples updated); #[fai_module] stays as a delegating alias so modules written before the rename keep compiling. 0.2.1. Signed-off-by: flemming-it <sf@flemming.it>
60 lines
2.2 KiB
Markdown
60 lines
2.2 KiB
Markdown
# chain-module-sdk
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Stable, ergonomic Rust surface for writing Ch∆In modules.
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A module written against this crate looks like:
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```rust
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use chain_module_sdk::prelude::*;
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#[chain_module]
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fn invoke(_ctx: Context, inputs: Inputs) -> Result<Outputs, ModuleError> {
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let text = inputs.require_text("input")?;
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Ok(Outputs::new().with_text("output", format!("echo: {text}")))
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}
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```
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That single function — plus a `Cargo.toml` listing
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`chain-module-sdk` as a dependency — is the entire module. The
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`#[chain_module]` macro generates the `wit_bindgen` invocation, the
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`Guest` implementation, the type conversions, and the
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`wit_bindgen::export!` glue behind the scenes.
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## What the SDK gives you
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| You get | Instead of |
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|---------|-----------|
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| `Inputs::require_text("name")` | manual `match payload { Payload::Text(s) => ..., _ => ... }` |
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| `Outputs::new().with_json(...)?` | building `Vec<(String, Payload)>` by hand |
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| `ModuleError::invalid_input("...")` | constructing WIT `invocation-error` variants |
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| `ctx.emit("progress", ...)` | hand-rolling the `host.emit-event` import (WIT 1.1) |
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| `#[chain_module]` | `wit_bindgen::generate!` + `Guest` impl + `export!` + `#![allow(unsafe_op_in_unsafe_fn)]` |
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## Stability
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The SDK insulates module code from the underlying WIT contract
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(`chain:platform`, currently v1.1 — frozen base v1.0 plus the
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additive 1.1 `emit-event` import). The WIT may evolve in
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additive minor versions or, eventually, a coordinated v2.0; the
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SDK absorbs that change so existing module code keeps compiling.
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The SDK ships its own copy of `wit/world.wit` so that the
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proc-macro can embed the contract via `include_str!` at compile
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time. A snapshot test (`crates/chain-module-sdk/tests/wit_freeze.rs`)
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asserts the SHA-256 matches the platform's frozen hash — if the
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two ever drift, CI fails.
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## Versioning
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| Track | Stability |
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|-------|-----------|
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| WIT contract (`chain:platform`) | v1.1; base frozen at v1.0, minors are additive |
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| `chain-module-sdk` Rust API | Semver; v0.x while ergonomics evolve |
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| Per-module versions | Each module repo's own concern |
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## License
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Apache-2.0. See `LICENSE`.
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Author: Dr. Stefan Flemming, Flemming.AI <chain@flemming.ai>
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Repository: https://git.flemming.ai/fai/chain-module-sdk-rust
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