fix(rest): Keep custom endpoints in resource().extend({...}) result type

[ntucker]

Requested by Nathaniel · project thread

Motivation

Customizing a resource's standard endpoints with .extend({ ... }) kept every endpoint at runtime, but TypeScript lost the ones added before it with .extend('name', options), and the deprecated create.

const UserResource = resource({ path: '/users/:id', schema: User })
  .extend('current', { path: '/user' })
  .extend({ get: { dataExpiryLength: 60000 } });

// Before: Property 'current' does not exist
// After: no error
const me = await ctrl.fetch(UserResource.current);

Solution

The object form of Extendable.extend() now returns CustomResource<...> & Omit<R, keyof ResourceInterface | 'extend'> (also in the TS 4.0/4.1 legacy declaration). Omit is used inline rather than a new helper alias so declaration emit in user code (declaration: true) can still name the type.

New typescript-tests/extendOptions.test.ts covers this, plus regression tests that extend() options are type-checked (dataExpiryLength: 'long' etc.) across RestEndpoint.extend(), resource().extend('key', ...) and resource().extend({ get }).

Verification:

• Zero loss: every diagnostic with all @ts-expect-error neutralized is identical before/after on TS 6, except the fixed Property 'current' does not exist.
• Probed on TS 4.0, 4.1, 4.4, 4.9, 5.3 (legacy declarations) and TS 6/7.
• Type perf (TS 6 instantiations): new 40-resource .extend('current').extend({ get }) scenario 153,915 → 156,556 (+1.7%, previously 40 errors); resources unchanged at 134,294; typical 12,995 → 13,398.

Open questions

From the original brief, two other gaps were checked:

• ep.extend({ dataExpiryLength: 'long' }) already fails on master on every TS version from 4.0 to 7 (the message reads "not assignable to type 'never'"). This PR only adds regression tests for it.
• getOptimisticResponse returning any is not fixed here. The right return type is the raw input the schema normalizes, which is what typed Controller.set() computes in core/src/controller/setManyTypes.ts. That file is being reworked for the set() updater perf regression, so sharing it is queued as a follow-up.

🤖 Generated with Claude Code

https://claude.ai/code/session_0117wFk9RgsnzgqUgJHDepyY

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Generated by Claude Code

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Note

Low Risk
Types-only change in @data-client/rest with no runtime behavior change; slightly richer intersection types (~1.7% more TS instantiations in one stress scenario).

Overview
Fixes a TypeScript-only gap when chaining resource().extend('name', …) with resource().extend({ get: … }) (or other standard endpoint overrides): runtime still had every endpoint, but the object-form return type was only CustomResource<…>, so names like current and deprecated create disappeared from the type.

The object overload of extend() now returns CustomResource<…> & Omit<R, keyof ResourceInterface | 'extend'> in resourceExtendable.ts and the TS 4.1 legacy declarations, so prior custom members stay on the inferred resource type through further chaining.

Adds typescript-tests/extendOptions.test.ts for member preservation and for extend() option validation regressions, plus a patch changeset and a v0.19 blog bullet.

^{Reviewed by Cursor Bugbot for commit e1f1930. Bugbot is set up for automated code reviews on this repo. Configure here.}

[changeset-bot]

🦋 Changeset detected

Latest commit: e1f1930

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

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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Size Change: 0 B

Total Size: 103 kB

ℹ️ View Unchanged

Filename	Size
examples/test-bundlesize/dist/App.js	1.46 kB
examples/test-bundlesize/dist/polyfill.js	307 B
examples/test-bundlesize/dist/rdcClient.js	10.9 kB
examples/test-bundlesize/dist/rdcEndpoint.js	8.07 kB
examples/test-bundlesize/dist/rdcNextjs.js	12.3 kB
examples/test-bundlesize/dist/rdcPipeableStream.js	9.64 kB
examples/test-bundlesize/dist/react.js	59.7 kB
examples/test-bundlesize/dist/webpack-runtime.js	784 B

_{compressed-size-action}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.08%. Comparing base (74a964e) to head (e1f1930).
⚠️ Report is 17 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4184      +/-   ##
==========================================
+ Coverage   98.06%   98.08%   +0.02%     
==========================================
  Files         163      165       +2     
  Lines        3098     3139      +41     
  Branches      617      625       +8     
==========================================
+ Hits         3038     3079      +41     
  Misses         18       18              
  Partials       42       42              

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