fix(types): Fix endpoint/rest legacy type errors with skipLibCheck off

[ntucker]

Requested by Nathaniel · project thread

Follow-up from #4138 (based on #4122's branch; retargets to master once #4122 merges).

Motivation

Before: with skipLibCheck: false, @data-client/endpoint and @data-client/rest declarations reported errors on TypeScript 4.0–4.5, and on 4.0/4.1 an Entity couldn't be an Endpoint schema (stale 4.0 overlays). CI never noticed because every typetest uses skipLibCheck: true.

After: no errors on 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.7, 4.8, 4.9, 5.0, 5.3, 5.4, and CI now fails if a legacy output regresses.

import { Endpoint, Entity, schema } from '@data-client/endpoint';

class User extends Entity {
  id = '';
  type = 'users';
}
const getUser = new Endpoint(
  (id: string) => fetch(`/users/${id}`).then(res => res.json()),
  { schema: User },
);
const feed = new schema.Union({ users: User }, 'type');

// Before (TypeScript 4.0, skipLibCheck: false):
//   error TS2456: Type alias 'RemoveArray' circularly references itself.
//   error TS2322: Type 'typeof User' is not assignable to type 'EntityInterface<any>'.
// Before (TypeScript 4.2):
//   error TS2344: Type 'TBase' does not satisfy the constraint 'new (...args: any) => any'.
// After: no errors

Solution

• TS 4.0 (no recursive conditional types): RemoveArray and PartialArray move to their own tupleTypes.ts module (PartialArray is still re-exported from utility), so the 4.0 overlay src-4.0-types/tupleTypes.d.ts replaces just those two types, like NoInfer.ts does. RemoveArray is unrolled up to 3 bound args (bind() still types the remaining params); PartialArray is approximated with Partial.
• TS < 4.2 stale overlays: src-4.0-types/schemas/{Entity,EntityTypes}.d.ts were hand copies whose only change was abstract new → new, and had drifted (old normalize/denormalize signatures). build-legacy-types.sh now does that rewrite on the downleveled output for versions below 4.2 (downlevel-dts misses it, 0.11 included), so those copies are deleted and can't go stale again. ts3.4 output improves too.
• TS 4.2 (lib InstanceType only accepts concrete new): EntityTypes/EntityMixin use a new internal ConstructorInstance<>, identical to the 4.3+ lib InstanceType. (AbstractInstanceType<> isn't a drop-in: it resolves constructor type aliases to any.)
• TS 4.2–4.4: UnionInstance's Args drops its EntityFields constraint (only used for queryKey args; the default is unchanged).
• TS 4.0–4.5 (found while verifying, not in the original list): RestEndpoint.getPage passes Extract<O['paginationField'], string>, since those versions don't narrow O['paginationField'] in the true branch.
• CI: esmodule-types (4.0, 4.1, 4.3, 4.8, 5.3) also runs examples/todo-app/tsconfig.typetest-libcheck.json, a standalone consumer of endpoint/normalizr/rest with skipLibCheck: false and types: [] (so @types/react etc. stay out of it). Checked that it fails on fix(types): Apply newer legacy type overlays to older TS outputs #4138's outputs (4.0, 4.1, 4.3) and passes here. ci-config.mdc updated.

Validated: root tsc --project tsconfig.test.json, lint, endpoint/rest/normalizr/graphql unit tests (one EntityMixin.test.ts @ts-expect-error placement fails locally with and without this change; CI is green).

Open questions

TS 3.x (ts3.4/, untested in CI) still reports pre-existing SnapshotInterface.d.ts rest-element errors; not addressed here.

🤖 Generated with Claude Code

https://claude.ai/code/session_01AMEHZGboXdMFRkF4D2ktki

[changeset-bot]

🦋 Changeset detected

Latest commit: ac19e20

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 10 packages

Name	Type
@data-client/endpoint	Patch
@data-client/rest	Patch
@data-client/graphql	Patch
example-benchmark	Patch
example-benchmark-react	Patch
normalizr-github-example	Patch
normalizr-redux-example	Patch
normalizr-relationships	Patch
test-bundlesize	Patch
coinbase-lite	Patch

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs-site	Ignored	Preview	Oct 4, 2026 3:22am UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.87%. Comparing base (db068cd) to head (ac19e20).

Additional details and impacted files

@@                      Coverage Diff                      @@
##           claude/project-thread-bw2hx0    #4140   +/-   ##
=============================================================
  Coverage                         97.87%   97.87%           
=============================================================
  Files                               156      156           
  Lines                              3057     3057           
  Branches                            612      612           
=============================================================
  Hits                               2992     2992           
  Misses                               18       18           
  Partials                             47       47           

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