fix(router-generator): avoid zod function schema for routeTreeFileFooter

[CaliLuke]

Summary

Replace the routeTreeFileFooter function schema in @tanstack/router-generator with a cross-version callable guard.

The current config schema uses z.function().returns(z.array(z.string())), which is a Zod v3-style function schema API and causes compatibility issues for consumers on Zod v4 in this package context.

This change narrows the fix to the actual runtime requirement for routeTreeFileFooter: it only needs to accept either:

• string[]
• a callable that returns string[]

At runtime, the generator only distinguishes between those two shapes:

• Array.isArray(config.routeTreeFileFooter)
• otherwise invoke config.routeTreeFileFooter()

So a typed callable guard is sufficient here and avoids consumer-side patching of installed package files.

Changes

• replace z.function().returns(z.array(z.string())) with z.custom<() => string[]>((value) => typeof value === 'function')
• add config tests covering both array and function forms of routeTreeFileFooter

Why

A downstream consumer currently has to patch the published package after install to keep their app working with Zod v4. This change removes the need for that workaround in the router-generator config surface.

Verification

Ran locally:

• pnpm --dir packages/router-generator exec vitest run tests/config.test.ts
• pnpm --dir packages/router-generator test:types
• pnpm --dir packages/router-generator test:eslint
• pnpm --dir packages/router-generator test:build

All passed.

Summary by CodeRabbit

• New Features

  • The routeTreeFileFooter configuration parameter now accepts both static string arrays and factory functions that dynamically return string arrays, providing greater flexibility in defining route tree footer content at configuration time.

• Tests

  • Added test coverage to verify correct behavior when routeTreeFileFooter is provided as either a static array or a factory function, ensuring proper value preservation.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 3bf8ffa8-1a7f-448b-bf90-0e2c8051644a

📥 Commits

Reviewing files that changed from the base of the PR and between 4ea2a62 and c96cfdb.

📒 Files selected for processing (2)

• packages/router-generator/src/config.ts
• packages/router-generator/tests/config.test.ts

---

📝 Walkthrough

Walkthrough

The pull request introduces schema validation support for routeTreeFileFooter to accept both string arrays and factory functions that return string arrays. A new internal validation schema is added alongside two test cases verifying the updated behavior.

Changes

Cohort / File(s)	Summary
Schema Validation packages/router-generator/src/config.ts	Added internal stringArrayFactorySchema to validate factory functions returning string arrays; updated routeTreeFileFooter union to accept both direct arrays and factory functions.
Test Coverage packages/router-generator/tests/config.test.ts	Added two test cases verifying getConfig accepts routeTreeFileFooter as a factory function and direct array, with proper value preservation.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A schema learns to dance and bend,
Functions and arrays now blend,
Factories spin their clever way,
Validation flourishes today!
✨ One more path, one more friend.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: replacing a Zod function schema with a custom guard for routeTreeFileFooter, which is the primary objective of the PR.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

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🧪 Generate unit tests (beta)

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• Post copyable unit tests in a comment

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[github-actions]

Bundle Size Benchmarks

• Commit: 4ea2a62787d0
• Measured at: 2026-03-07T17:35:16.204Z
• Baseline source: history:4ea2a62787d0
• Dashboard: bundle-size history

Scenario	Current (gzip)	Delta vs baseline	Raw	Brotli	Trend
react-router.minimal	86.84 KiB	0 B (0.00%)	273.33 KiB	75.44 KiB	▁▁▁▁▁██████
react-router.full	89.88 KiB	0 B (0.00%)	283.67 KiB	78.18 KiB	▁▁▁▁▁██████
solid-router.minimal	36.17 KiB	0 B (0.00%)	108.44 KiB	32.49 KiB	▁▁▁▁▁██████
solid-router.full	40.50 KiB	0 B (0.00%)	121.49 KiB	36.40 KiB	▁▁▁▁▁██████
vue-router.minimal	52.03 KiB	0 B (0.00%)	148.42 KiB	46.71 KiB	▁▁▁▁▁██████
vue-router.full	56.85 KiB	0 B (0.00%)	164.01 KiB	51.04 KiB	▁▁▁▁▁██████
react-start.minimal	99.40 KiB	0 B (0.00%)	312.48 KiB	85.98 KiB	▁▁▁▁▁██████
react-start.full	102.78 KiB	0 B (0.00%)	322.29 KiB	88.82 KiB	▁▁▁▁▁██████
solid-start.minimal	48.49 KiB	0 B (0.00%)	146.03 KiB	42.85 KiB	▁▁▁▁▁██████
solid-start.full	53.96 KiB	0 B (0.00%)	161.98 KiB	47.51 KiB	▁▁▁▁▁██████

Trend sparkline is historical gzip bytes ending with this PR measurement; lower is better.

[nx-cloud]

View your CI Pipeline Execution ↗ for commit c96cfdb

Command	Status	Duration	Result
nx affected --targets=test:eslint,test:unit,tes...	✅ Succeeded	13m 9s	View ↗
nx run-many --target=build --exclude=examples/*...	✅ Succeeded	48s	View ↗

---

☁️ Nx Cloud last updated this comment at 2026-03-08 08:19:46 UTC

[pkg-pr-new]

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commit: a3356e2

[codspeed-hq]

Merging this PR will not alter performance

✅ 6 untouched benchmarks

---

_{Comparing CaliLuke:lucacandela/autok-128-router-generator-zod4 (c96cfdb) with main (4ea2a62)}

[CaliLuke]

@tannerlinsley anything else I need to do to get this patch upstreamed?