fix(rest): Fix type errors when using concrete body types with subclassed RestEndpoint

[ntucker]

Motivation

Subclassing RestEndpoint with O extends RestGenerics = any — the standard pattern for adding auth headers, custom serialization, etc. — produced type errors when specifying concrete body types. PathArgs<any> evaluated to KeysToArgs<string> ({[x:string]: string|number}), a restrictive index-signature that rejected concrete body objects.

This was introduced in #3782 (TypeScript 6 upgrade), where [O['searchParams']] extends [undefined] tuple wrapping was added to prevent undefined→any widening in non-strict mode. That fix was correct for union types, but regressed the O = any case.

Solution

Add unknown extends S ? any as the first branch in PathArgs and PathArgsAndSearch. This detects any specifically (unknown extends any is true, unknown extends string is false) and short-circuits to any, allowing normal type inference for subclassed endpoints.

Uses unknown extends S instead of the standard 0 extends 1 & T IsAny pattern because the latter doesn't resolve correctly inside constrained generic parameters (S extends string) in TypeScript 6.

Changes:

• pathTypes.ts: Add unknown extends S ? any guard to PathArgs and PathArgsAndSearch
• pathTypes.test.ts: Assert PathArgs<any> and PathArgsAndSearch<any> equal any
• types.test.ts: Add inheritance tests with AuthdEndpoint<O extends RestGenerics = any> covering constructor, extend, and path changes with concrete body types

Open questions

N/A

Made with Cursor

---

Note

Low Risk
Type-level changes to PathArgs/PathArgsAndSearch affect TypeScript inference for generic path values; runtime behavior is unchanged and coverage is added via TS tests.

Overview
Fixes a TypeScript regression where subclassing RestEndpoint with O extends RestGenerics = any caused overly-restrictive path arg inference, which then rejected concrete body types.

Updates PathArgs and PathArgsAndSearch to short-circuit to any when the path type is any, and adds TypeScript tests covering PathArgs<any> plus common subclassing/extend() scenarios. Generated playground .d.ts types are updated accordingly, and a patch changeset documents the fix.

^{Written by Cursor Bugbot for commit 3f62c46. This will update automatically on new commits. Configure here.}

[changeset-bot]

🦋 Changeset detected

Latest commit: 3f62c46

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

This PR includes changesets to release 4 packages

Name	Type
@data-client/rest	Patch
example-benchmark-react	Patch
test-bundlesize	Patch
coinbase-lite	Patch

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Project	Deployment	Actions	Updated (UTC)
docs-site	Ready	Preview, Comment	Apr 1, 2026 1:31pm

[github-actions]

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

_{compressed-size-action}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.08%. Comparing base (ea9bb2d) to head (0e44fd9).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3845   +/-   ##
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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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