refactor(price-alert): port to Host trait + MockHost tests (BLEU-851)#22
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refactor(price-alert): port to Host trait + MockHost tests (BLEU-851)#22brunota20 wants to merge 1 commit into
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Validates the host-trait pattern from the M3 tutorial end-to-end on
a real module. The price-alert example now matches the recipe the
tutorial recommends:
modules/examples/price-alert/
├── Cargo.toml adds shepherd-sdk-test as dev-dep
└── src/
├── lib.rs wit_bindgen::generate! + WitBindgenHost
│ adapter + From conversions + Guest impl
└── strategy.rs pure logic against `&impl Host`
+ parse_config + scale_threshold + tests
Strategy logic now takes `&impl shepherd_sdk::host::Host` and never
calls `nexum::host::*` free functions directly. The wit-bindgen
boilerplate (WitBindgenHost struct, ChainHost / LocalStoreHost /
CowApiHost / LoggingHost impls, convert_err / sdk_err_into_wit /
convert_level helpers) lives in lib.rs - mechanical and identical
across modules, a future declarative macro in shepherd-sdk will
elide it.
parse_config now returns `Result<Settings, shepherd_sdk::host::
HostError>` instead of `Result<T, String>`. Carrying the SDK error
through the strategy / adapter / Guest seam means the same domain /
kind / code / message / data fields surface to the operator
verbatim.
Tests: 16 (was 11) - all strategy tests now run against
shepherd_sdk_test::MockHost rather than calling wit-bindgen
directly. The 5 new ones lock the on_block behaviour end-to-end:
- idle when price is on the safe side of the trigger
- triggers below threshold (Direction::Below)
- triggers above threshold (Direction::Above)
- warns + continues on RPC timeout (no propagation into the
supervisor)
- warns on undecodable oracle response
- respects `every_n_blocks` throttle
cargo clippy --all-targets --workspace -- -D warnings clean. .wasm
210 KB (was 206 KB; +4 KB for the adapter boilerplate, which
deduplicates against shepherd-sdk so future modules add no extra
cost).
This was referenced Jun 17, 2026
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Summary
Closes the loop opened by BLEU-841 (mock host) + BLEU-846 (example) + BLEU-848 (tutorial). The price-alert module now matches the recipe the tutorial recommends.
```
modules/examples/price-alert/
├── Cargo.toml + shepherd-sdk-test as dev-dep
└── src/
├── lib.rs wit_bindgen::generate! + WitBindgenHost
│ adapter + From conversions + Guest impl
└── strategy.rs pure logic against
&impl Host+ parse_config + scale_threshold + tests
```
What changed
strategy.rsand takes&impl shepherd_sdk::host::Host. No direct `nexum::host::*` calls in there.lib.rscarries the wit-bindgen adapter boilerplate (will be folded into a declarative macro in shepherd-sdk in a future cleanup).Numbers
.wasmThe .wasm grows by 4 KB because of the adapter boilerplate; alloy + shepherd-sdk dedupe so future modules pay zero extra.
Stacks on #21 (rust-idiomatic pass).
Linear: BLEU-851.
Test plan