Do not wrap pointer-to-struct functool inputs

[PratikDhanave]

Summary

inputFormatFor (tool/functool/func.go) wraps any input whose Kind is not reflect.Struct in inputWrapper[T]. A pointer-to-struct handler has Kind == reflect.Ptr, so it gets wrapped — producing a nested {"Arg0":{...}} schema and rejecting the flat arguments that the equivalent value-receiver handler accepts:

type In struct{ V string `json:"v"` }
functool.MustNew(cfg, func(ctx context.Context, in *In) (string, error) { ... }).
    Call(ctx, `{"v":"hi"}`)
// → validation error: validating root: unexpected additional properties ["v"]

This contradicts jsonformat.ForType, which deliberately dereferences pointers at the root ("Pointers are treated equivalently to non-pointers … with no benefit" to wrapping the root object). So *Struct and Struct handlers should produce the same flat schema, but today only Struct does.

Fix

Dereference pointers before the struct check, so only genuinely non-struct inputs are wrapped.

Public API

No exported symbols change.

Tests

Adds TestFuncTool_PointerStructInput_UsesFlatSchema (black-box): a *struct handler accepts flat arguments. It fails before this change (schema validation rejects the flat args) and passes after.

[Copilot]

Pull request overview

This PR aligns functool input schema generation with jsonformat.ForType by ensuring pointer-to-struct (*Struct) handler inputs are treated the same as value struct (Struct) inputs, avoiding an unnecessary root-level wrapper schema that breaks flat JSON arguments.

Changes:

• Dereference pointer types before deciding whether to wrap the input type in inputWrapper[T].
• Preserve wrapping only for genuinely non-struct root inputs.
• Add a black-box test proving *struct handlers accept flat JSON arguments.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tool/functool/func.go	Dereferences pointer inputs before the struct-kind check to prevent *struct from being wrapped and producing nested schemas.
tool/functool/func_test.go	Adds a regression test validating that *struct inputs use a flat schema and accept flat JSON args.

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