# Changelog — einherjar/core

All notable changes to this module are documented here.
Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
This module adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

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## [1.0.0] — 2026-05-28

### Added

#### `launcher`

- `Launcher` interface — `Append`, `BeforeStart`, `Run`, `Shutdown`
- `New(logger logging.Logger, opts ...Options) Launcher` — constructs the lifecycle
  orchestrator; takes `contracts/logging.Logger` (not the concrete `logz` type)
- `Hook` type (`func() error`) — assembly-phase callback registered via `BeforeStart`
- `Config` struct — `ComponentStopTimeout time.Duration` with `env:"EINHERJAR_COMPONENT_STOP_TIMEOUT" envDefault:"15s"` (`caarlos0/env` syntax)
- Startup banner — printed to stdout before any slog output; disabled via
  `EINHERJAR_BANNER=off` or `EINHERJAR_BANNER=false`
- Components accepted as `lifecycle.Component` from `contracts` — not a locally
  defined interface; any type that satisfies `contracts/lifecycle.Component` is
  directly compatible

#### `logz`

- `Config` struct — `Level slog.Level`, `JSON bool`, `StaticArgs []any`, `Writer io.Writer`
  - `Level` and `JSON` carry `env` and `envDefault` tags (`caarlos0/env` syntax); `StaticArgs` and `Writer` are programmatic-only fields without tags
  - Env vars: `EINHERJAR_LOG_LEVEL` (default `INFO`), `EINHERJAR_LOG_JSON` (default `false`)
- `New(cfg Config) logging.Logger` — returns `contracts/logging.Logger`; the
  concrete `slogLogger` struct is unexported
- Error enrichment — when the error passed to `Logger.Error` satisfies
  `errs.CodedError` or `errs.ContextualError` (from `contracts/errs`), the
  corresponding `error_code` field and context key-value pairs are automatically
  appended to the log record; this replaces the private duck-typed bridge used in
  micro-lib's `logz`
- Context helpers — `WithRequestID`, `GetRequestID`, `WithField`, `WithFields`
- `Logger.WithContext(ctx)` — extracts `request_id` and extra fields from context
  and attaches them to every subsequent log record

#### `xerrors`

- `Code` type (stable string wire values, gRPC-aligned)
- **16 error code constants** — complete gRPC canonical set plus `ErrGone` (HTTP 410)
  - New over micro-lib: `ErrOutOfRange` (gRPC OUT_OF_RANGE, HTTP 400),
    `ErrAborted` (gRPC ABORTED, HTTP 409), `ErrDataLoss` (gRPC DATA_LOSS, HTTP 500)
- `Code.Description()` — human-readable description for each code
- `Err` struct — `code`, `message`, `err` (cause), `fields` (context), `platformCode`
- Base constructors: `New(code, message)`, `Wrap(code, message, err)`
- **16 convenience constructors** (one per code): `InvalidInput`, `OutOfRange`,
  `Unauthorized`, `PermissionDenied`, `NotFound`, `AlreadyExists`, `Aborted`,
  `Gone`, `PreconditionFailed`, `RateLimited`, `Cancelled`, `Internal`, `DataLoss`,
  `NotImplemented`, `Unavailable`, `DeadlineExceeded`
- Builder methods: `WithContext`, `WithError`, `WithPlatformCode`
- Accessors: `Code()`, `Message()`, `Fields()`, `PlatformCode()`, `Detailed()`
- Standard interfaces: `error`, `Unwrap`, `json.Marshaler`
- Compile-time assertions: `var _ errs.CodedError = (*Err)(nil)` and
  `var _ errs.ContextualError = (*Err)(nil)` — formalises the duck-type bridge
  from micro-lib into an explicit, verifiable contract

#### `valid`

- `Validator` interface — `Struct(v any) error`
- `New(opts ...Option) Validator` — constructs a validator backed by
  `go-playground/validator/v10` (backend is hidden; never exposed in the public API)
- `MessageProvider` interface — `Message(field, tag, param string) string`
- `DefaultMessages` — built-in English message provider
- `SpanishMessages` — opt-in Spanish message provider
- `Option` type and `WithMessageProvider(mp MessageProvider) Option`
- `FieldLevel` interface — passed to custom validator functions; exposes `Field() reflect.Value`, `Param() string`, `FieldName() string`; go-playground backend never visible
- `WithCustomValidator(tag string, fn func(FieldLevel) bool) Option` — registers a custom validation tag at construction time; panics on empty or conflicting tag
- `OverrideProvider(handlers map[string]func(field, param string) string, base MessageProvider) MessageProvider` — composes a tag→message handler map with a fallback; use for custom tag messages without re-implementing built-ins
- **Full built-in tag coverage** in `DefaultMessages` and `SpanishMessages` — all go-playground/validator tags have specific messages (fields, network, strings, format, comparisons, other; ~150 tags total)
- Field names in error context prefer the json struct tag, falling back to the Go
  field name
- Error codes: `ErrInvalidInput` for constraint failures, `ErrInternal` for
  non-struct arguments — both returned as `*xerrors.Err`

### Design Notes

1. **Contracts as the source of truth.** `launcher` accepts `lifecycle.Component`
   and `logging.Logger` from `contracts`. It does not define its own lifecycle
   interface. Any type that satisfies the contracts interface is directly compatible —
   no adapters needed.

2. **Duck typing replaced by explicit interfaces.** micro-lib's `logz` detected
   enrichable errors via private `errorWithCode`/`errorWithContext` interfaces.
   `core/logz` detects them via `contracts/errs.CodedError` and `contracts/errs.ContextualError`.
   The decoupling (logz does not import xerrors) is preserved; the contract is now
   visible. See [ADR-002](docs/adr/ADR-002-logz-contracts-errs.md).

3. **Complete gRPC error code set.** micro-lib's `xerrors` had 13 codes. `core/xerrors`
   adds the three missing gRPC codes (`OUT_OF_RANGE`, `ABORTED`, `DATA_LOSS`) and
   provides a named convenience constructor for every code — `New()` and `Wrap()` are
   reserved for edge cases.

4. **One module, four sub-packages.** The consolidation eliminates four-way version
   coordination for a set of packages that always ship and upgrade together.
   See [ADR-001](docs/adr/ADR-001-core-module-composition.md).

5. **Startup banner.** The launcher prints an ASCII art banner to stdout before any
   structured log output. It is disabled via `EINHERJAR_BANNER=off`, not via code
   changes, so production deployments can suppress it without modifying the service.

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[1.0.0]: https://code.nochebuena.dev/einherjar/core/releases/tag/v1.0.0