Upgrading

All six @amqp-contract/* packages version together, so upgrade them in lockstep. This page summarizes the changes that require action; the full history lives in the GitHub Releases and each package's CHANGELOG.md.

2.1.x → 2.2.x

Upgrades unthrown to 3.0.0. amqp-contract's own public surface is unchanged. Action is only needed if you author qualify mappers that intentionally route unexpected failures to the Defect channel:

• The standalone Defect constructor is no longer exported.
• qualify now receives a defect callback as its second argument: (cause, defect) => E | defect(cause).

- import { fromPromise, Defect } from "unthrown";
- fromPromise(work(), (cause) => isExpected(cause) ? new MyError(cause) : Defect(cause));
+ import { fromPromise } from "unthrown";
+ fromPromise(work(), (cause, defect) => isExpected(cause) ? new MyError(cause) : defect(cause));

Mappers that only return a modeled error (the common case) are unaffected. If you depend on unthrown directly, bump it to ^3.0.0 so a single copy is shared.

2.0.x → 2.1.x

Upgrades unthrown to 2.0.0, which is additive (adds the AsyncResult value namespace, flatTapErr, isResult). No code changes required.

1.x → 2.0

Upgrades unthrown to 1.0.0, which renames the value constructors — ok → Ok, err → Err, defect → Defect (the lowercase forms are removed). Update every call site that constructs results directly:

- import { ok, err } from "unthrown";
- return ok(undefined).toAsync();
- return err(new RetryableError("...")).toAsync();
+ import { Ok, Err } from "unthrown";
+ return Ok(undefined).toAsync();
+ return Err(new RetryableError("...")).toAsync();

The .match({ ok, err, defect }) handler keys stay lowercase — those are case branches, not constructors. Everything else (fromPromise, fromSafePromise, .unwrap(), .isOk(), …) is unchanged.

0.x → 1.0

Replaces neverthrow with unthrown across all packages. unthrown keeps the errors-as-values model but adds a third Defect channel for unexpected failures. If you consume the Result / AsyncResult values returned by the client, worker, or core, update your call sites:

neverthrow (amqp-contract 0.x)	unthrown (amqp-contract 1.x)
ResultAsync<T, E>	AsyncResult<T, E>
result.match(okFn, errFn)	result.match({ ok, err, defect })
.andThen / .andTee / .orTee	.flatMap / .tap / .tapErr
okAsync(v) / errAsync(e)	ok(v).toAsync() / err(e).toAsync()
ResultAsync.fromPromise(p, mapper)	fromPromise(p, qualify) (free function, mapper required)
._unsafeUnwrap() / ._unsafeUnwrapErr()	.unwrap() / .unwrapErr()
error instanceof HandlerError	isHandlerError(error) (HandlerError is now a union type)

The table shows the constructors as they were on amqp-contract 1.x (lowercase ok / err); if you're upgrading straight to 2.0+, use the capitalized Ok / Err forms from the 1.x → 2.0 section instead.

Error classes (TechnicalError, RetryableError, …) became TaggedErrors with namespaced tags (e.g. "@amqp-contract/TechnicalError") for exhaustive dispatch via matchTags; their Error.name and constructors are unchanged.

See the Error Model guide for the full picture of how results flow through the API.