# routes/shared/strip-undefined — drop undefined-valued keys

## Purpose

Bridges Zod's optional-field semantics
(`.optional() → string | undefined`) with the suaveplan
`@suaveplan/contacts` input shapes, which use
`exactOptionalPropertyTypes: true` and therefore forbid the
`| undefined` half of optional members. Returning a shallow copy with
`undefined` keys removed lets the route handlers feed Zod output
directly into `repo.create({ ...stripUndefined(parsed.data), tenantId })`
without losing type safety.

Without this helper every route handler would need to manually
re-build the input object key-by-key, or every Zod schema would have
to redefine its optionality via `.transform()`. The helper is the
focused fix.

## Features

- Shallow — preserves nested undefineds because the consumer Zod
  schemas only produce top-level optionals.
- Preserves `null`, `0`, `""`, and `false` (only `undefined` is dropped).
- Pure / type-safe — returns `Partial<T>`-compatible shape.

## Usage: Basic

```ts
import { stripUndefined } from "@suaveplan/api-plugin-contacts";

const parsed = CreateContactSchema.parse(input);
const repoInput = stripUndefined(parsed);
await repo.create({ ...repoInput, tenantId });
```

## Usage: Advanced

```ts
import { stripUndefined } from "@suaveplan/api-plugin-contacts";

function safeMerge<T extends Record<string, unknown>>(base: T, patch: Partial<T>): T {
    return { ...base, ...stripUndefined(patch) } as T;
}
```

## API Reference

- `stripUndefined<T>(input: T): { [K in keyof T]?: T[K] }` — shallow
  copy with `undefined` keys omitted.

## Implementation Notes

- Uses `Object.entries` so symbol-keyed properties are ignored; route
  inputs are always plain objects so this is fine.
- Does not deep-clone — the returned object shares nested references
  with the input.
- The return type widens to `Partial<T>` for ergonomics; the runtime
  contract is stricter (any non-`undefined` original value flows
  through unchanged).