fix(rest): Guard RestEndpoint against O=any in subclassed constructors

[ntucker]

Follows up on #3845.

Motivation

#3845 fixed PathArgs<any> returning a restrictive index-signature type, but the any also propagates through the searchParams conditional in RestEndpoint<O> and RestEndpointConstructorOptions<O>. When subclassing with O extends RestGenerics = any, the [O['searchParams']] extends [undefined] non-distributive wrapper (added in #3782 for TS6) prevents any from passing through, producing the same restrictive type at a higher level.

Solution

Add unknown extends O ? any : guard before the searchParams conditional in both RestEndpoint<O> and RestEndpointConstructorOptions<O>. This catches O = any before it reaches PathArgs, so subclassed endpoints accept concrete body types.

Includes a detailed comment explaining a known limitation: TypeScript may partially infer O from constructor arguments, widening path literals (e.g., '/users/:id') to string (the RestGenerics constraint) instead of preserving the literal. This is inherent to TypeScript's class constructor inference with complex conditional parameter types and would require restructuring the constructor options type to fix.

Open questions

N/A

Made with Cursor

---

Note

Low Risk
Low risk: this is a TypeScript type-level change plus additional type tests; runtime behavior is unaffected, but it could subtly change inference/acceptance for code that relied on previous any propagation.

Overview
Fixes a TypeScript typing regression where subclassing RestEndpoint with O extends RestGenerics = any could cause any to be blocked by the searchParams conditional and yield overly restrictive URL-param/body types.

Adds an unknown extends O ? any : ... guard to both RestEndpoint and RestEndpointConstructorOptions to restore expected any behavior, and expands the TypeScript test to cover subclassed endpoints with both param and static paths (GET/POST) to ensure concrete body types remain accepted.

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Size Change: 0 B

Total Size: 80.9 kB

ℹ️ View Unchanged

Filename	Size
examples/test-bundlesize/dist/App.js	3.44 kB
examples/test-bundlesize/dist/polyfill.js	307 B
examples/test-bundlesize/dist/rdcClient.js	10.4 kB
examples/test-bundlesize/dist/rdcEndpoint.js	6.35 kB
examples/test-bundlesize/dist/react.js	59.7 kB
examples/test-bundlesize/dist/webpack-runtime.js	726 B

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.08%. Comparing base (9b6c7f4) to head (68b8b29).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3847   +/-   ##
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  Coverage   98.08%   98.08%           
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  Files         152      152           
  Lines        2871     2871           
  Branches      563      563           
=======================================
  Hits         2816     2816           
  Misses         11       11           
  Partials       44       44           

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