fix(test): Fixture args accept readonly tuples by ntucker · Pull Request #4250 · reactive/data-client

ntucker · 2026-10-06T15:34:23Z

Requested by Nathaniel · project thread

Motivation

Fixtures written with args: [...] as const failed to type-check when passed to MockResolver, renderDataHook(), renderDataCompose() or mockInitialState() ("The type 'readonly [...]' is 'readonly' and cannot be assigned to the mutable type"). #4246 had to drop as const from docs examples to get them checking, and the root and packages/react README "Integrated data mocking" snippets use exactly this shape.

const fixtures = [
  {
    endpoint: TodoResource.getList,
    args: [{ userId: 1 }] as const,
    response: [{ id: 1, title: 'Write tests', userId: 1 }],
  },
];

// Before: type error on `fixtures`. After: works as written
<MockResolver fixtures={fixtures}>
  <TodoList />
</MockResolver>;

Solution

SuccessFixtureEndpoint.args and ErrorFixtureEndpoint.args are Readonly<Parameters<E>> in @data-client/core/mock and @data-client/test; core's internal dispatchFixture takes readonly any[]. Interceptors take args as function params, so they're unaffected.
Restores as const in the MockResolver and unit-testing docs examples, updates the Fixtures API reference, regenerates skill references and playground editor types.
New fixtures typeperf scenario (100 fixture sets with mutable and as const args, typed Fixture<E>, interceptors, MockResolver, mockInitialState).

Type-check cost (TS 7, fixtures scenario): with as const removed, 74,851 → 74,937 instantiations (+0.11%). As written, master reports 500 errors; this branch 0 errors at 76,837 (new budget entry; other budget entries untouched).

Zero loss: every diagnostic with @ts-expect-error neutralized is identical before and after on tsconfig.test.json, both examples' typetests and app tsconfigs (946 lines, empty diff). A scratch check of typed and untyped as const fixtures passes on TS 4.8, 5.3, 6 and 7, and on 4.0 apart from a pre-existing loose arg check in rest's legacy 4.0 types (unchanged by this PR).

🤖 Generated with Claude Code

https://claude.ai/code/session_01K9dm6BAco8rRjbd6aLcJZB

Generated by Claude Code

Note

Low Risk
Narrow TypeScript-only widening for fixture args; runtime mock behavior is unchanged aside from accepting readonly arrays at compile time.

Overview
Fixture args are typed as Readonly<Parameters<E>> instead of mutable Parameters<E> in @data-client/core and @data-client/test, and mockInitialState’s internal dispatchFixture now accepts readonly any[]. That lets test fixtures use args: [...] as const with MockResolver, mockInitialState(), renderDataHook(), and Vue’s renderDataCompose() without TypeScript assignability errors.

Docs, agent skill references, and playground editor .d.ts files mirror the API change and restore as const in examples. A changeset records patch bumps for core, test, react, and vue. CI typeperf adds a fixtures scenario (mutable and as const args, interceptors, typed fixtures) with a new budget.json entry.

^{Reviewed by Cursor Bugbot for commit 27f7017. Bugbot is set up for automated code reviews on this repo. Configure here.}

Fixtures written with `args: [...] as const` were rejected because `args` was typed as the mutable `Parameters<E>`. Type it as `Readonly<Parameters<E>>` in @data-client/core/mock and @data-client/test, restore `as const` in the docs examples #4246 dropped, and add a `fixtures` typeperf scenario. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01K9dm6BAco8rRjbd6aLcJZB

vercel · 2026-10-06T15:34:30Z

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated
docs-site	Ready	Preview	Oct 6, 2026 3:36pm UTC

chatgpt-codex-connector · 2026-10-06T15:34:36Z

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-06T15:36:36.240107Z	`27f7017`	PR opened

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

Open a pull request for review
Mark a draft as ready
Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

ntucker · 2026-10-06T15:35:05Z

Staff engineer (Cursor agent): LGTM at 27f7017. Widening args to Readonly<Parameters<E>> is the minimal, correct fix: mutable tuples still assign to it, response/interceptors keep spreading Parameters<E>, and nothing at runtime mutates args. The zero-diff diagnostic check across TS versions and the new fixtures typeperf budget (+0.11% instantiations on the like-for-like run) are good evidence, and restoring as const in the docs undoes the #4246 workaround instead of leaving it as drift.

FOLLOW_UP (not for this PR): SuccessFixtureEndpoint / ErrorFixtureEndpoint are still hand-copied in packages/core/src/mock/fixtureTypes.ts and packages/test/src/fixtureTypes.ts, and this PR had to make the identical edit in both. I assume the copy exists because @data-client/test still peers on @data-client/react ^0.12.15. When that floor next moves to a version whose core ships core/mock, @data-client/test can re-export those types instead of duplicating them, so the next fixture typing change lands once.

github-actions · 2026-10-06T15:36:58Z

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`	12.4 kB
`examples/test-bundlesize/dist/rdcPipeableStream.js`	9.7 kB
`examples/test-bundlesize/dist/react.js`	59.7 kB
`examples/test-bundlesize/dist/webpack-runtime.js`	784 B

_{compressed-size-action}

github-actions

Benchmark React

Details

Benchmark suite	Current: `27f7017`	Previous: `f992c21`	Ratio
`data-client: getlist-100`	`136.99` ops/s (`± 4.1%`)	`139.87` ops/s (`± 5.1%`)	`1.02`
`data-client: getlist-500`	`45.45` ops/s (`± 3.2%`)	`41.75` ops/s (`± 3.9%`)	`0.92`
`data-client: update-entity`	`392.31` ops/s (`± 8.4%`)	`363.76` ops/s (`± 7.6%`)	`0.93`
`data-client: update-user`	`350.99` ops/s (`± 10.0%`)	`312.5` ops/s (`± 6.2%`)	`0.89`
`data-client: getlist-500-sorted`	`45.56` ops/s (`± 9.1%`)	`42.3` ops/s (`± 9.8%`)	`0.93`
`data-client: update-entity-sorted`	`344.83` ops/s (`± 6.6%`)	`298.57` ops/s (`± 5.1%`)	`0.87`
`data-client: update-entity-multi-view`	`357.14` ops/s (`± 7.1%`)	`303.31` ops/s (`± 8.8%`)	`0.85`
`data-client: list-detail-switch-10`	`9.07` ops/s (`± 12.5%`)	`6.71` ops/s (`± 6.5%`)	`0.74`
`data-client: update-user-10000`	`74.36` ops/s (`± 14.8%`)	`70.92` ops/s (`± 11.8%`)	`0.95`
`data-client: invalidate-and-resolve`	`36.5` ops/s (`± 5.7%`)	`35.4` ops/s (`± 6.3%`)	`0.97`
`data-client: unshift-item`	`217.39` ops/s (`± 5.9%`)	`192.31` ops/s (`± 7.1%`)	`0.88`
`data-client: delete-item`	`303.03` ops/s (`± 5.3%`)	`270.27` ops/s (`± 6.1%`)	`0.89`
`data-client: move-item`	`181.82` ops/s (`± 8.7%`)	`168.08` ops/s (`± 9.9%`)	`0.92`

This comment was automatically generated by workflow using github-action-benchmark.

codecov · 2026-10-06T15:38:24Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.10%. Comparing base (a588e9d) to head (27f7017).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4250   +/-   ##
=======================================
  Coverage   98.10%   98.10%           
=======================================
  Files         166      166           
  Lines        3166     3166           
  Branches      626      626           
=======================================
  Hits         3106     3106           
  Misses         18       18           
  Partials       42       42

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

github-actions

Benchmark

Details

Benchmark suite	Current: `27f7017`	Previous: `f992c21`	Ratio
`normalizeLong`	`536` ops/sec (`±3.39%`)	`529` ops/sec (`±3.12%`)	`0.99`
`normalizeLong Values`	`462` ops/sec (`±1.12%`)	`458` ops/sec (`±0.66%`)	`0.99`
`normalizeLong Scalar`	`444` ops/sec (`±2.74%`)	`438` ops/sec (`±2.95%`)	`0.99`
`normalizeLong Scalar update`	`1109` ops/sec (`±0.33%`)	`1109` ops/sec (`±0.35%`)	`1`
`denormalizeLong`	`295` ops/sec (`±5.76%`)	`277` ops/sec (`±5.86%`)	`0.94`
`denormalizeLong Values`	`272` ops/sec (`±4.97%`)	`263` ops/sec (`±3.98%`)	`0.97`
`denormalizeLong donotcache`	`1335` ops/sec (`±1.55%`)	`1371` ops/sec (`±0.63%`)	`1.03`
`denormalizeLong Values donotcache`	`947` ops/sec (`±0.21%`)	`925` ops/sec (`±1.35%`)	`0.98`
`denormalizeLong Scalar donotcache`	`1527` ops/sec (`±0.37%`)	`1477` ops/sec (`±0.37%`)	`0.97`
`denormalizeShort donotcache 500x`	`1761` ops/sec (`±0.07%`)	`1657` ops/sec (`±0.91%`)	`0.94`
`denormalizeShort 500x`	`722` ops/sec (`±5.74%`)	`708` ops/sec (`±6.66%`)	`0.98`
`denormalizeShort 500x withCache`	`9204` ops/sec (`±0.09%`)	`9194` ops/sec (`±1.81%`)	`1.00`
`queryShort 500x withCache`	`4334` ops/sec (`±0.06%`)	`4209` ops/sec (`±0.21%`)	`0.97`
`buildQueryKey All`	`67328` ops/sec (`±0.52%`)	`65146` ops/sec (`±0.60%`)	`0.97`
`query All withCache`	`7321` ops/sec (`±3.29%`)	`7783` ops/sec (`±2.29%`)	`1.06`
`denormalizeLong with mixin Entity`	`271` ops/sec (`±7.42%`)	`250` ops/sec (`±6.64%`)	`0.92`
`denormalizeLong withCache`	`9424` ops/sec (`±0.22%`)	`9591` ops/sec (`±0.93%`)	`1.02`
`denormalizeLong withCache (Scalar churn)`	`9311` ops/sec (`±0.76%`)	`9512` ops/sec (`±0.85%`)	`1.02`
`denormalizeLong Values withCache`	`8331` ops/sec (`±1.06%`)	`8300` ops/sec (`±1.18%`)	`1.00`
`denormalizeLong Scalar withCache`	`9631` ops/sec (`±0.17%`)	`9765` ops/sec (`±0.24%`)	`1.01`
`denormalizeLong Scalar update withCache`	`7238` ops/sec (`±0.46%`)	`7183` ops/sec (`±0.59%`)	`0.99`
`denormalizeLong All withCache`	`8225` ops/sec (`±0.18%`)	`8152` ops/sec (`±0.36%`)	`0.99`
`denormalizeLong Query-sorted withCache`	`7737` ops/sec (`±2.70%`)	`8157` ops/sec (`±2.05%`)	`1.05`
`denormalizeLongAndShort withEntityCacheOnly`	`2024` ops/sec (`±0.24%`)	`2036` ops/sec (`±0.26%`)	`1.01`
`denormalize bidirectional 50`	`5193` ops/sec (`±10.41%`)	`5082` ops/sec (`±10.27%`)	`0.98`
`denormalize bidirectional 50 donotcache`	`57453` ops/sec (`±0.21%`)	`56500` ops/sec (`±0.21%`)	`0.98`
`getResponse`	`6262` ops/sec (`±5.53%`)	`6497` ops/sec (`±3.96%`)	`1.04`
`getResponse (null)`	`12763374` ops/sec (`±0.44%`)	`13044398` ops/sec (`±0.44%`)	`1.02`
`getResponse (clear cache)`	`248` ops/sec (`±7.66%`)	`236` ops/sec (`±7.93%`)	`0.95`
`getSmallResponse`	`5068` ops/sec (`±1.07%`)	`4987` ops/sec (`±1.08%`)	`0.98`
`getSmallInferredResponse`	`3879` ops/sec (`±0.53%`)	`3886` ops/sec (`±0.21%`)	`1.00`
`getResponse Collection`	`7041` ops/sec (`±1.43%`)	`6885` ops/sec (`±1.87%`)	`0.98`
`get Collection`	`4534` ops/sec (`±0.28%`)	`4168` ops/sec (`±0.28%`)	`0.92`
`get Query-sorted`	`7462` ops/sec (`±2.69%`)	`7342` ops/sec (`±3.52%`)	`0.98`
`setLong`	`529` ops/sec (`±0.21%`)	`528` ops/sec (`±0.33%`)	`1.00`
`setLongWithMerge`	`311` ops/sec (`±1.01%`)	`302` ops/sec (`±0.82%`)	`0.97`
`setLongWithSimpleMerge`	`327` ops/sec (`±0.52%`)	`325` ops/sec (`±1.20%`)	`0.99`
`setSmallResponse 500x`	`1121` ops/sec (`±1.48%`)	`1100` ops/sec (`±1.83%`)	`0.98`
`setMany 50x one-per-row`	`148` ops/sec (`±0.27%`)	`147` ops/sec (`±1.73%`)	`0.99`
`setMany 50 batch`	`4479` ops/sec (`±0.64%`)	`4502` ops/sec (`±0.58%`)	`1.01`
`setMany 500x one-per-row`	`15.17` ops/sec (`±0.44%`)	`14.91` ops/sec (`±0.43%`)	`0.98`
`setMany 500 batch`	`1823` ops/sec (`±0.29%`)	`1822` ops/sec (`±1.06%`)	`1.00`

This comment was automatically generated by workflow using github-action-benchmark.

ntucker self-assigned this Oct 6, 2026

vercel Bot deployed to Preview October 6, 2026 15:36 View deployment

github-actions Bot reviewed Oct 6, 2026

View reviewed changes

ntucker merged commit fc4b015 into master Oct 6, 2026
33 checks passed

ntucker deleted the claude/project-thread-pbehtu branch October 6, 2026 16:15

Navigation Menu

Repository navigation

fix(test): Fixture args accept readonly tuples - #4250

fix(test): Fixture args accept readonly tuples#4250
ntucker merged 1 commit into
masterfrom
claude/project-thread-pbehtu

ntucker commented Oct 6, 2026 •

edited by cursor Bot

Loading

Uh oh!

vercel Bot commented Oct 6, 2026 •

edited

Loading

Uh oh!

chatgpt-codex-connector Bot commented Oct 6, 2026 •

edited

Loading

Uh oh!

ntucker commented Oct 6, 2026

Uh oh!

github-actions Bot commented Oct 6, 2026

Uh oh!

github-actions Bot left a comment

Uh oh!

codecov Bot commented Oct 6, 2026

Uh oh!

github-actions Bot left a comment

Uh oh!

Uh oh!

This branch was successfully deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

ntucker commented Oct 6, 2026 • edited by cursor Bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Motivation

Solution

Uh oh!

vercel Bot commented Oct 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

chatgpt-codex-connector Bot commented Oct 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Codex Review Summary

Uh oh!

ntucker commented Oct 6, 2026

Uh oh!

github-actions Bot commented Oct 6, 2026

Uh oh!

github-actions Bot left a comment

Choose a reason for hiding this comment

Benchmark React

Uh oh!

codecov Bot commented Oct 6, 2026

Codecov Report

Uh oh!

github-actions Bot left a comment

Choose a reason for hiding this comment

Benchmark

Uh oh!

Uh oh!

This branch was successfully deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

ntucker commented Oct 6, 2026 •

edited by cursor Bot

Loading

vercel Bot commented Oct 6, 2026 •

edited

Loading

chatgpt-codex-connector Bot commented Oct 6, 2026 •

edited

Loading