fix(types): fix the type definitions for factory models and config, a… by liyown · Pull Request #408 · TanStack/ai

liyown · 2026-03-29T17:13:25Z

🎯 Changes

fix #407

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested this code locally with pnpm run test:pr.

Summary by CodeRabbit

Bug Fixes
- Adapter factories now preserve all parameters that follow the model argument (including required positional arguments such as credentials and label metadata), preventing dropped arguments and restoring expected call behavior.
Refactor
- Improved internal typing and factory inference to reliably retain and surface existing parameters after the model without altering runtime behavior.

coderabbitai · 2026-03-29T17:13:38Z

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packages/ai/tests/extend-adapter.test.ts

📝 Walkthrough

Walkthrough

Rewrites extendAdapter's TypeScript inference to extract model names and preserve all parameters after the model; updates the exported overloads and widens the implementation signature. Adds a changeset documenting the fix and a test asserting required args after the model are preserved.

Changes

Adapter factory parameters preservation fix

Layer / File(s)	Summary
Changeset documentation `.changeset/fix-extend-adapter-rest-args.md`	A patch changeset documents the fix where `extendAdapter` now preserves factory parameters that appear after the model argument, including labels and optionality.
Type inference utilities `packages/ai/src/extend-adapter.ts`	Adds `AnyAdapterFactory`, `InferFactoryModels`, `InferAdapterReturn`, `InferRestArgs`, and composes `ExtendedFactory` to union model names and preserve rest parameters and return types.
Export overloads and implementation signature `packages/ai/src/extend-adapter.ts`	Changes exported `extendAdapter` overload to return `ExtendedFactory<TFactory, TDefs>` and widens the implementation to `AnyAdapterFactory`; runtime behavior remains a passthrough to the original factory.
Type-level tests for post-model args `packages/ai/tests/extend-adapter.test.ts`	Adds `mockChat(model, apiKey, config?)` tests that assert the extended factory keeps `apiKey` required, `config` optional, and enforces invalid-model type errors.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 I nibbled types with gentle care,
Rest args kept safe from thin air,
Models extended, not a one lost,
Hop—extendAdapter fixed at no cost! 🥕

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title indicates a fix to type definitions for factory models and config, which directly aligns with the main change to extendAdapter's type inference.
Description check	✅ Passed	The description is minimal but references the linked issue `#407` and confirms required checklist items were completed.
Linked Issues check	✅ Passed	The PR successfully addresses issue `#407` by fixing type inference for extendAdapter with chat factories, preserving required parameters after the model argument.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the extendAdapter type definitions to preserve parameters, matching the scope defined in issue `#407`.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@packages/typescript/ai/src/extend-adapter.ts`:
- Line 113: The generic constraint for InferRestArgs uses an invalid
rest-parameter type; update the constraint on TFactory from using (...args: any)
to a valid rest tuple type such as (...args: any[]) => any so TypeScript accepts
it. Locate the type alias InferRestArgs and change its constraint to TFactory
extends (...args: any[]) => any (and if other similar generic constraints exist
in the same file, apply the same tuple/array rest fix).

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Push a commit to this branch (recommended)
Create a new PR with the fixes

ℹ️ Review info

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Reviewing files that changed from the base of the PR and between a8a4465 and 0ccbcdf.

📒 Files selected for processing (1)

packages/typescript/ai/src/extend-adapter.ts

coderabbitai · 2026-03-29T17:17:13Z

+/**
+ * Extracts all parameter types after the first parameter from a function.
+ */
+type InferRestArgs<TFactory extends (...args: any) => any> =


⚠️ Potential issue | 🔴 Critical

🧩 Analysis chain

🌐 Web query:

Does TypeScript allow a rest parameter type annotation of any(e.g.,(...args: any) => any), or must it be an array/tuple type like any[]?

💡 Result:

No, TypeScript does not allow a rest parameter type annotation of any like (...args: any) => any. The type annotation for rest parameters must be an array type like any[], a specific array type such as number[], or a tuple type.

Citations:

1: https://www.typescriptlang.org/docs/handbook/2/functions.html

2: https://www.typescriptlang.org/docs/handbook/functions.html

3: https://www.typescriptlang.org/docs/handbook/2/functions

🏁 Script executed:

head -n 120 packages/typescript/ai/src/extend-adapter.ts | tail -n 20

Repository: TanStack/ai

Length of output: 541

Fix invalid rest-parameter typing in generic constraint.

Line 113 uses (...args: any), but TypeScript requires rest parameters to be array or tuple types (e.g., any[]). This will cause a TypeScript compilation error.

Suggested fix

-type InferRestArgs<TFactory extends (...args: any) => any> = +type InferRestArgs<TFactory extends (...args: any[]) => any> = Parameters<TFactory> extends [any, ...infer Rest] ? Rest : []

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

type InferRestArgs<TFactory extends (...args: any) => any> =

type InferRestArgs<TFactory extends (...args: any[]) => any> =

Parameters<TFactory> extends [any, ...infer Rest] ? Rest : []

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed. In `@packages/typescript/ai/src/extend-adapter.ts` at line 113, The generic constraint for InferRestArgs uses an invalid rest-parameter type; update the constraint on TFactory from using (...args: any) to a valid rest tuple type such as (...args: any[]) => any so TypeScript accepts it. Locate the type alias InferRestArgs and change its constraint to TFactory extends (...args: any[]) => any (and if other similar generic constraints exist in the same file, apply the same tuple/array rest fix).

…nd add InferRestArgs utility type

…ving unused InferConfig type

…, add regression test Review follow-ups for TanStack#408: - InferRestArgs now matches [any?, ...] so factories with an optional first parameter don't silently drop their trailing args - Extract the extended signature into a named ExtendedFactory type and restore an explicit return type on extendAdapter (no cast needed) - Add a regression test for 3-parameter factories like createAnthropicChat(model, apiKey, config?) (TanStack#407) - Add a patch changeset for @tanstack/ai Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Replace any-typed function shapes with a sound AnyAdapterFactory constraint built on never params / unknown return (parameters are contravariant, so never accepts every factory). The deliberate model-union widening now lives in an overload signature instead of an unchecked assignment, so no cast or any remains anywhere in the file. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

…ories Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tombeckenham

Thank you so much for supplying the PR for this @liyown. I've locked down the types a bit further to remove type any - which we're actively trying to weed out of the codebase.

coderabbitai Bot reviewed Mar 29, 2026

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tombeckenham self-assigned this May 29, 2026

15367279252qq.com and others added 3 commits June 4, 2026 21:01

fix(types): fix the type definitions for factory models and config, a…

033ddf7

…nd add InferRestArgs utility type

refactor(types): simplify type definitions for factory models by remo…

8633c8a

…ving unused InferConfig type

tombeckenham force-pushed the fix/fix-extend-adapter-error-infer-type branch from 0ccbcdf to 865a2e8 Compare June 4, 2026 11:17

tombeckenham force-pushed the fix/fix-extend-adapter-error-infer-type branch from 3735a3f to b391615 Compare June 4, 2026 11:32

test(types): assert invalid model names are rejected for 3-param fact…

c345a73

…ories Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tombeckenham approved these changes Jun 5, 2026

View reviewed changes

tombeckenham merged commit c0af426 into TanStack:main Jun 5, 2026
3 checks passed

github-actions Bot mentioned this pull request Jun 5, 2026

ci: Version Packages #703

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fix(types): fix the type definitions for factory models and config, a…#408

fix(types): fix the type definitions for factory models and config, a…#408
tombeckenham merged 5 commits into
TanStack:mainfrom
liyown:fix/fix-extend-adapter-error-infer-type

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	type InferRestArgs<TFactory extends (...args: any) => any> =
	type InferRestArgs<TFactory extends (...args: any[]) => any> =
	Parameters<TFactory> extends [any, ...infer Rest] ? Rest : []

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liyown commented Mar 29, 2026 •

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