Sails IDL Client

Goal

Keep Sails builders on the typed pipeline for IDL generation, Rust client generation, and integration wiring.

If a released contract evolves or a new deployed contract version is introduced, keep the generated-client path compatible with the approved cutover plan instead of assuming one regenerated client can replace all consumers immediately.

Default JS Or TS Path

• Treat the program .idl as the source of truth for the interface.
• Generate the normal client with sails-js or sails-cli so the workspace gets lib.ts and typed program or service classes instead of hand-written payload code.
• Pair the generated client with GearApi from @gear-js/api for node connectivity.
• Use parseIdl from the sails-js and sails-js-parser path only when you explicitly need dynamic runtime control rather than pre-generated files.

Build Script Path

• Check the repo's build.rs before inventing a manual IDL step.
• For a dedicated Rust client crate, prefer the standard Sails build-helper path:
  • [build-dependencies] sails-rs = { version = "...", features = ["build"] }
  • fn main() { sails_rs::build_client::<Program>(); }
• Treat direct sails-idl-gen plus sails-client-gen-v2 wiring as a manual fallback for non-standard layouts or explicitly custom generation needs.
• Do not assume a single fixed output location. Depending on the repo, generated .idl and Rust client artifacts may land in OUT_DIR, the client crate output path, or another repo-defined location.

Generated Client Pitfalls

• Custom BTreeMap key types: Public IDL-facing map keys should prefer primitive or tuple types (e.g. u64, (u32, u32), ActorId). Custom struct keys (e.g. BTreeMap<Pos, V>) may fail client-side decoding because the generated type may lack the required ordered-key traits. Stick to primitives or tuples unless generated-client support for that custom key type is confirmed.

Released Contract Evolution

• Treat each .idl as the interface contract for one deployed program version.
• If a new deployed contract version changes the public surface, do not assume every consumer can switch at once.
• Keep old and new generated clients available during cutover when frontend, tests, scripts, or migration tooling still depend on the previous version.
• Regenerate clients as part of release work, but do not treat regeneration alone as compatibility validation.

Frontend IDL Handoff

When a Sails program's IDL is consumed by a frontend in a separate workspace or repo:

• Check in an IDL snapshot in the frontend project so the frontend toolchain can build independently.
• Document the refresh command: after regenerating the IDL from the Rust workspace, copy it to the frontend snapshot location and regenerate the TypeScript client.
• If the IDL is only generated in OUT_DIR during Rust builds, it will not be available to the frontend at build time.

See ../../references/sails-idl-client-pipeline.md for the canonical frontend export pattern.

Inputs

• ../../references/sails-idl-v2-syntax.md — IDL v2 grammar, annotations, types, service/program declarations
• ../../references/sails-header-wire-format.md — Sails Header layout, interface/entry ID derivation, wire examples
• ../../references/sails-cheatsheet.md
• ../../references/sails-idl-client-pipeline.md
• ../../assets/task-plan-template.md
• ../../references/contract-interface-evolution.md

Route Here When

• Check build.rs or generation wiring when it no longer generates the expected artifacts
• the client crate drifted from program changes
• Check output paths and artifact freshness before deeper debugging
• tests are building raw payloads instead of using generated clients
• local smoke needs a typed client path

Guardrails

• Keep generated artifacts aligned with the program contract before deeper debugging.
• Prefer generated client flows in tests and smoke runs when the workspace supports them.
• Do not treat sails-js as a runtime target; it is the JavaScript client library used by generated and dynamic IDL-driven flows.
• Do not replace the standard path with raw ABI, ethers-style bindings, or hand-written SCALE payloads for a standard Vara Sails app.
• Do not treat missing codegen as a reason to bypass the Sails pipeline.
• Do not document sails-idl-gen + sails-client-gen-v2 as the default dedicated-client path when the repo can use sails-rs build helpers.