TanStack: Fix createServerFn validator mock

[sjh9714]

Closes #35174

What I did

Adds support for the TanStack Start createServerFn().validator(...).handler(...) chain in the @storybook/tanstack-react Start mock. The mock already treated inputValidator as a no-op builder step; validator now behaves the same way so stories using the documented TanStack Start validator syntax do not crash before handler() is mocked.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

No manual UI testing is needed for this mock-builder change. To verify manually, add a story or imported module that defines a server function with createServerFn().validator(...).handler(...); Storybook should load it without createServerFn(...).validator is not a function.

Commands run:

• yarn install --immutable
• yarn nx compile core
• yarn vitest run --config code/frameworks/tanstack-react/vitest.config.ts code/frameworks/tanstack-react/src/export-mocks/start.test.ts (failed before the fix with createServerFn(...).validator is not a function, then passed after the fix)
• cd code && yarn fmt:write
• yarn nx compile eslint-plugin
• yarn --cwd code lint:js:cmd frameworks/tanstack-react/src/export-mocks/start.ts frameworks/tanstack-react/src/export-mocks/start.test.ts
• yarn vitest run --config code/frameworks/tanstack-react/vitest.config.ts code/frameworks/tanstack-react/src/export-mocks/start.test.ts code/frameworks/tanstack-react/src/export-mocks/react-router.test.ts
• yarn nx compile tanstack-react
• yarn nx check tanstack-react
• yarn vitest run code/frameworks/tanstack-react/src/export-mocks/start.test.ts

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Note: I used Codex while preparing this change, reviewed the final diff, and ran the listed checks locally.

Summary by CodeRabbit

• Tests

  • Added test verifying server function creation supports validator chain syntax patterns.

• Chores

  • Extended mock server-function builder with a validator method to support fluent API patterns consistent with existing chainable methods.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 30976c70-5f5e-41e4-a486-c69c33bbfaa0

📥 Commits

Reviewing files that changed from the base of the PR and between beab22c and 3c58fb6.

📒 Files selected for processing (2)

• code/frameworks/tanstack-react/src/export-mocks/start.test.ts
• code/frameworks/tanstack-react/src/export-mocks/start.ts

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📝 Walkthrough

Walkthrough

Adds a validator chainable method to the internal createMockServerFnBuilder in the TanStack React framework mock, following the existing pattern for options, middleware, and inputValidator. A corresponding Vitest test verifies the validator(...).handler(...) chain resolves correctly.

Changes

createServerFn mock validator chain

Layer / File(s)	Summary
builder.validator method and chain test code/frameworks/tanstack-react/src/export-mocks/start.ts, code/frameworks/tanstack-react/src/export-mocks/start.test.ts	Adds builder.validator returning a new createMockServerFnBuilder() instance at line 591–594, and a test asserting createServerFn().validator(...).handler(...) resolves to 'ok'.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

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[sjh9714]

The Danger failure is only asking for labels, but I don't have permission to add labels to this repo. Could a maintainer add the appropriate labels? Suggested based on this fix: bug, ci:normal, and qa:needed.

[theoludwig]

Any news? Would be cool to get this PR merged. cc @ndelangen @huang-julien @valentinpalkovic

[huang-julien]

👍

[storybook-app-bot]

Package Benchmarks

^{Commit: af767bd, ran on 17 July 2026 at 12:20:42 UTC}

The following packages have significant changes to their size or dependencies:

storybook

	Before	After	Difference
Dependency count	73	73	0
Self size	21.32 MB	22.16 MB	🚨 +835 KB 🚨
Dependency size	36.44 MB	36.44 MB	0 B
Bundle Size Analyzer	Link	Link

@storybook/ember

	Before	After	Difference
Dependency count	187	187	0
Self size	13 KB	15 KB	🚨 +2 KB 🚨
Dependency size	30.94 MB	30.94 MB	🎉 -652 B 🎉
Bundle Size Analyzer	Link	Link

@storybook/nextjs

	Before	After	Difference
Dependency count	533	533	0
Self size	640 KB	663 KB	🚨 +23 KB 🚨
Dependency size	62.27 MB	62.31 MB	🚨 +34 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/nextjs-vite

	Before	After	Difference
Dependency count	93	93	0
Self size	1.37 MB	1.39 MB	🚨 +22 KB 🚨
Dependency size	23.97 MB	24.01 MB	🚨 +38 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/react-native-web-vite

	Before	After	Difference
Dependency count	122	122	0
Self size	29 KB	30 KB	🚨 +940 B 🚨
Dependency size	25.04 MB	25.08 MB	🚨 +38 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/react-vite

	Before	After	Difference
Dependency count	83	83	0
Self size	32 KB	36 KB	🚨 +4 KB 🚨
Dependency size	21.75 MB	21.78 MB	🚨 +34 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/react-webpack5

	Before	After	Difference
Dependency count	274	274	0
Self size	23 KB	23 KB	🚨 +777 B 🚨
Dependency size	48.06 MB	48.09 MB	🚨 +34 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/tanstack-react

	Before	After	Difference
Dependency count	84	84	0
Self size	112 KB	110 KB	🎉 -2 KB 🎉
Dependency size	21.78 MB	21.82 MB	🚨 +38 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/cli

	Before	After	Difference
Dependency count	205	205	0
Self size	827 KB	827 KB	🚨 +84 B 🚨
Dependency size	91.32 MB	92.15 MB	🚨 +834 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/codemod

	Before	After	Difference
Dependency count	198	198	0
Self size	32 KB	32 KB	🎉 -115 B 🎉
Dependency size	89.80 MB	90.63 MB	🚨 +835 KB 🚨
Bundle Size Analyzer	Link	Link

create-storybook

	Before	After	Difference
Dependency count	74	74	0
Self size	1.09 MB	1.09 MB	🎉 -720 B 🎉
Dependency size	57.77 MB	58.60 MB	🚨 +835 KB 🚨
Bundle Size Analyzer	node	node

@storybook/react

	Before	After	Difference
Dependency count	59	59	0
Self size	1.49 MB	1.52 MB	🚨 +35 KB 🚨
Dependency size	12.45 MB	12.45 MB	🚨 +81 B 🚨
Bundle Size Analyzer	Link	Link