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

.changeset/legacy-ts-endpoint-libcheck.md

@@ -0,0 +1,30 @@
+---
+'@data-client/endpoint': patch
+'@data-client/rest': patch
+'@data-client/graphql': patch
+---
+
+Fix more TypeScript 4.x errors when `skipLibCheck` is off
+
+[Entity](https://dataclient.io/rest/api/Entity), [Endpoint](https://dataclient.io/rest/api/Endpoint), [Union](https://dataclient.io/rest/api/Union) and [RestEndpoint](https://dataclient.io/rest/api/RestEndpoint) declarations no longer report errors on TypeScript 4.0 through 4.5. On TypeScript 4.0 and 4.1, an `Entity` can be an `Endpoint` schema again.
+
+```ts
+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
+```

.circleci/config.yml

@@ -329,6 +329,8 @@ jobs:
             fi
             yarn run tsc --project examples/todo-app/tsconfig.typetest.json
             yarn run tsc --project examples/github-app/tsconfig.typetest.json
+            # skipLibCheck: false, so the legacy typesVersions outputs get checked too
+            yarn run tsc --project examples/todo-app/tsconfig.typetest-libcheck.json
 
   esmodule-types-latest:
     executor: node

.cursor/rules/ci-config.mdc

@@ -12,7 +12,12 @@ alwaysApply: false
 - Jobs halt via the `halt-unless-relevant-change` command based on flags computed once in `setup` (`.ci-esmodule-relevant`, `.ci-tests-relevant`) and transported via `save_cache`/`restore_cache` (keyed on `CIRCLE_SHA1`) so jobs can halt before paying `attach_workspace`. Missing/unreadable flags fail open (jobs run). On the default branch both flags are always true (a push may carry several commits). The diff uses `--no-renames` so moving a file out of a relevant dir still counts.
   - `esmodule` (validate-esmodule-browser-build, esmodule-types*): a denylist, so new paths fail open. False only when every changed path is provably outside the esmodule jobs' inputs: the shared `DOCS_ONLY` paths (also the `tests` denylist) plus `.vscode/`, `plans/`, root `__tests__/` (excluded by every `tsconfig.compile.json`), `eslint.config.mjs`, `jest.config.js`, `examples/*.md`, and examples the jobs never build (`benchmark`, `benchmark-react`, `coin-app`, `nextjs`, `normalizr-github`, `normalizr-redux`, `test-bundlesize`, `vue-todo-app`). Only add a path if no esmodule job (or the `setup` builds feeding them) reads it.
   - `tests` (lint, typecheck, unit_tests, node_matrix): false only when every changed path is docs/website/tooling (`website/`, `docs/`, `.changeset/`, `.cursor/`, `.agents/`, `.claude/`, `.github/`, root `*.md`), except `website/src/components/Playground/` (has unit tests). When both flags are false, `setup` halts before install.
-- Legacy TS types (`ci:build:legacy-types`, consumed by `esmodule-types`) build inside `setup` (`ci:build:setup:esmodule`) only when the esmodule flag is set; there is no separate job, to keep a job hop off the critical path. In CI it builds only endpoint/normalizr/rest outputs for TS >= 4.0 (`LEGACY_MIN_TS=4.0`), since the oldest TS in the `esmodule-types` matrix is 4.0; release builds (`build:types`) still emit every version. `scripts/build-legacy-types.sh` builds each TS version concurrently; each `ts<version>/` gets the downleveled `lib`, then every newer version's `src-*-types` overlay, then its own. Any change to legacy types building must leave `ts*/` output byte-identical to master (diff it) unless it intentionally changes published types (then add a changeset).
+- Legacy TS types (`ci:build:legacy-types`, consumed by `esmodule-types`):
+  - Built inside `setup` (`ci:build:setup:esmodule`) only when the esmodule flag is set; there is no separate job, to keep a job hop off the critical path.
+  - In CI only endpoint/normalizr/rest outputs for TS >= 4.0 are built (`LEGACY_MIN_TS=4.0`, the oldest TS in the `esmodule-types` matrix); release builds (`build:types`) still emit every version.
+  - `scripts/build-legacy-types.sh` builds each TS version concurrently; each `ts<version>/` gets the downleveled `lib` (with `abstract new` rewritten to `new` below 4.2, which `downlevel-dts` misses), then every newer version's `src-*-types` overlay, then its own. Keep overlays to small single-purpose modules (like `NoInfer.ts`, `tupleTypes.ts`) so whole-file copies can't go stale.
+  - `esmodule-types` also runs `examples/todo-app/tsconfig.typetest-libcheck.json` (`skipLibCheck: false`, `types: []`) so errors inside the legacy outputs fail CI; the other typetests use `skipLibCheck: true`.
+  - Any change to legacy types building must leave `ts*/` output byte-identical to master (diff it) unless it intentionally changes published types (then add a changeset).
 - Never `git fetch --depth` the base branch in the relevance check: a shallow fetch severs the merge base and the three-dot diff fails.
 - Changing root `package.json` `workspaces` requires updating the `setup` job's workspace trimming step.
 

examples/todo-app/tsconfig.typetest-libcheck.json

@@ -0,0 +1,16 @@
+{
+  // Standalone so it type-checks only @data-client declarations (and their deps)
+  // on every TypeScript in the esmodule-types matrix.
+  "compilerOptions": {
+    "target": "es2020",
+    "module": "esnext",
+    "lib": ["dom", "esnext"],
+    "moduleResolution": "node",
+    "strict": true,
+    "skipLibCheck": false,
+    "skipDefaultLibCheck": true,
+    "types": [],
+    "noEmit": true
+  },
+  "files": ["typetest-libcheck.ts"]
+}

examples/todo-app/typetest-libcheck.ts

@@ -0,0 +1,44 @@
+// Type-checks published declarations (including legacy typesVersions outputs)
+// with skipLibCheck: false; see tsconfig.typetest-libcheck.json
+import { Endpoint, Entity, schema } from '@data-client/endpoint';
+import { denormalize, MemoCache, normalize } from '@data-client/normalizr';
+import { resource, RestEndpoint } from '@data-client/rest';
+
+class User extends Entity {
+  id = '';
+  name = '';
+  type = 'users';
+}
+class Post extends Entity {
+  id = '';
+  title = '';
+  author = User.fromJS();
+  static schema = { author: User };
+}
+
+const getUser = new Endpoint(
+  (id: string) => Promise.resolve({ id, name: 'a', type: 'users' }),
+  { schema: User },
+);
+const twoArgs = new Endpoint((a: string, b: number) =>
+  Promise.resolve({ id: a, title: String(b) }),
+);
+const bound = twoArgs.bind(null, 'x');
+bound(5);
+// @ts-expect-error
+bound('wrong');
+
+const feed = new schema.Union({ users: User }, 'type');
+const PostResource = resource({
+  path: '/posts/:id',
+  schema: Post,
+  paginationField: 'cursor',
+});
+PostResource.getList.getPage({ cursor: 'a' });
+const search = new RestEndpoint({ path: '/search' });
+
+const memo = new MemoCache();
+const { result, entities } = normalize(Post, { id: '1', title: 'hi' });
+denormalize(Post, result, entities);
+
+export { getUser, feed, search, memo };

packages/endpoint/src-4.0-types/tupleTypes.d.ts

@@ -0,0 +1,14 @@
+// Recursive conditional types need TypeScript 4.1, so these are approximated
+
+export type PartialArray<A> = A extends any[] ? Partial<A> : never;
+
+/** Removes Rem's length worth of leading elements from Orig (up to 3) */
+export type RemoveArray<Orig extends any[], Rem extends any[]> =
+  Rem extends [] ? Orig
+  : Rem extends [any] ?
+    Orig extends [any, ...infer R] ? R : never
+  : Rem extends [any, any] ?
+    Orig extends [any, any, ...infer R] ? R : never
+  : Rem extends [any, any, any] ?
+    Orig extends [any, any, any, ...infer R] ? R : never
+  : any[];

packages/endpoint/src-4.2-types/endpointTypes.d.ts

@@ -7,6 +7,7 @@ import type {
   FetchFunction,
   PartialParameters,
 } from './types.js';
+import type { RemoveArray } from './tupleTypes.js';
 export interface EndpointOptions<
   F extends FetchFunction = FetchFunction,
   S extends Schema | undefined = undefined,
@@ -156,11 +157,5 @@ export interface ExtendableEndpointConstructor {
   ): EndpointInstanceInterface<F, S, M> & E;
   readonly prototype: Function;
 }
-type RemoveArray<Orig extends any[], Rem extends any[]> =
-  Rem extends [any, ...infer RestRem] ?
-    Orig extends [any, ...infer RestOrig] ?
-      RemoveArray<RestOrig, RestRem>
-    : never
-  : Orig;
 export {};
 //# sourceMappingURL=endpointTypes.d.ts.map

packages/endpoint/src/endpointTypes.ts

@@ -5,6 +5,7 @@ import type {
   FetchFunction,
   PartialParameters,
 } from './types.js';
+import type { RemoveArray } from './tupleTypes.js';
 
 export interface EndpointOptions<
   F extends FetchFunction = FetchFunction,
@@ -191,10 +192,3 @@ type IfAny<T, Y, N> = 0 extends 1 & T ? Y : N;
 type IfTypeScriptLooseNull<Y, N> = 1 | undefined extends 1 ? Y : N;
 
 type OnlyFirst<A extends unknown[]> = A extends [] ? [] : [A[0]];
-
-type RemoveArray<Orig extends any[], Rem extends any[]> =
-  Rem extends [any, ...infer RestRem] ?
-    Orig extends [any, ...infer RestOrig] ?
-      RemoveArray<RestOrig, RestRem>
-    : never
-  : Orig;

packages/endpoint/src/schema.d.ts

@@ -228,8 +228,8 @@ export interface UnionConstructor {
  */
 export interface UnionInstance<
   Choices extends EntityMap = any,
-  Args extends EntityFields<AbstractInstanceType<Choices[keyof Choices]>> =
-    EntityFields<AbstractInstanceType<Choices[keyof Choices]>>,
+  // unconstrained: TypeScript 4.2-4.4 can't prove UnionConstructor's Args satisfy EntityFields
+  Args = EntityFields<AbstractInstanceType<Choices[keyof Choices]>>,
 > {
   readonly _hoistable: true;
   define(definition: Schema): void;