# @suaveplan/i18n-formatter-display-name - Intl.DisplayNames wrapper for the @suaveplan/i18n family — locale-aware language/region/script/currency/calendar display names. Per-(locale, type, style, fallback) cache, Zod-validated options, OTel histogram + cache-hit counter, structured I18nError mapping. Universal leaf package.

## Summary

Wrapper around `Intl.DisplayNames` for the `@suaveplan/i18n` family —
locale-aware language, region, script, currency, and calendar display
names. Universal leaf package; depends only on
`@suaveplan/i18n-shared`, `@suaveplan/types`, `@suaveplan/error`,
`@opentelemetry/api`, and `zod`.

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## Documentation tree

- [formatter](./src/formatter/formatter.md) — `DisplayNameFormatter` and the `formatDisplayName` standalone helper expose `Intl.DisplayNames` for the `@suaveplan/i18…
  - [formatter](./src/formatter/formatter.md) — `DisplayNameFormatter` and the `formatDisplayName` standalone helper expose `Intl.DisplayNames` for the `@suaveplan/i18…
- [helpers](./src/helpers/helpers.md) — The five ergonomic helpers (`formatLanguageName`, `formatRegionName`, `formatCurrencyName`, `formatScriptName`, `format…
  - [helpers](./src/helpers/helpers.md) — The five ergonomic helpers (`formatLanguageName`, `formatRegionName`, `formatCurrencyName`, `formatScriptName`, `format…
- [observability](./src/observability/observability.md) — The DisplayName formatter exports two OpenTelemetry instruments and a small in-memory state ring so spec-conformance te…
  - [observability](./src/observability/observability.md) — The DisplayName formatter exports two OpenTelemetry instruments and a small in-memory state ring so spec-conformance te…
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## Why this exists

The 14-package i18n modular split (cross-cutting design
`2026-05-05-i18n-modular-split.md`) lifts each `Intl.*` wrapper out of
the monolith into its own sibling package. Lifting the display-name
helper out of `@suaveplan/i18n` lets consumers that only need
country-name / currency-name rendering pull a single small package
instead of the entire i18n core.

The package adds the canonical Wave-3 formatter shape on top of the
monolith's standalone helper: Zod-validated options, a per-(locale,
type, style, fallback) cache, OTel histogram + cache-hit counter, the
class wrapper for symmetry with `NumberFormatter` /
`RelativeTimeFormatter` / `ListFormatter` / `DateFormatter`, and five
ergonomic helpers that pre-bind `formatDisplayName` with each
canonical `type` value.

## Install

```bash
bun add @suaveplan/i18n-formatter-display-name
```

## Quick Start

```ts
import {
    DisplayNameFormatter,
    formatDisplayName,
    formatLanguageName,
    formatRegionName,
    formatCurrencyName,
} from "@suaveplan/i18n-formatter-display-name";

formatDisplayName("GB", "en-GB", { type: "region" }); // "United Kingdom"
formatLanguageName("fr", "en-GB"); // "French"
formatRegionName("US", "en-GB"); // "United States"
formatCurrencyName("USD", "en-GB"); // "US Dollar"

const f = new DisplayNameFormatter({ type: "region", style: "short" });
f.format("DE", "en-GB"); // "Germany"
```

## Modules

| Subpath | Description |
|---|---|
| `@suaveplan/i18n-formatter-display-name` | Root barrel — class + standalones + helpers + observability |
| `@suaveplan/i18n-formatter-display-name/formatter` | `DisplayNameFormatter`, `formatDisplayName`, types, schema |
| `@suaveplan/i18n-formatter-display-name/helpers` | Five ergonomic helpers — `formatLanguageName`, `formatRegionName`, `formatCurrencyName`, `formatScriptName`, `formatCalendarName` |

## Modules Documentation

- [formatter.md](src/formatter.md) — `DisplayNameFormatter` class, `formatDisplayName`, `clearDisplayNameCache`
- [helpers.md](src/helpers.md) — five ergonomic helpers
- [observability.md](src/observability.md) — OTel histogram + cache-hit counter

## Public Surface (snapshot)

| Export | Kind | Origin |
|---|---|---|
| `DisplayNameFormatter` | class | `formatter.ts` |
| `formatDisplayName` | function | `formatter.ts` |
| `clearDisplayNameCache` | function | `formatter.ts` |
| `DisplayNameFormatterOptionsSchema` | Zod schema | `formatter.schemas.ts` |
| `DisplayNameFormatterOptions` | type | `formatter.types.ts` |
| `DisplayNameType` | type | `formatter.types.ts` |
| `DisplayNameStyle` | type | `formatter.types.ts` |
| `DisplayNameFallback` | type | `formatter.types.ts` |
| `DisplayNameFormatterCacheKey` | type | `formatter.types.ts` |
| `formatLanguageName` | function | `helpers.ts` |
| `formatRegionName` | function | `helpers.ts` |
| `formatCurrencyName` | function | `helpers.ts` |
| `formatScriptName` | function | `helpers.ts` |
| `formatCalendarName` | function | `helpers.ts` |
| `recordDisplayNameFormat` | function | `observability.ts` |
| `recordDisplayNameCacheHit` | function | `observability.ts` |
| `getDisplayNameMetricsState` | function | `observability.ts` |
| `resetDisplayNameMetricsState` | function | `observability.ts` |

## Versioning

Part of the 14-package i18n modular-split rollout. Stays at `0.1.0`
until the slim core (Wave 6) cuts the family `1.0.0` release.