This library grew from a core idea: that by separating static error definitions (the "what") from dynamic instances (the "why"), we could resolve the common trade-offs between context, type identity, and boilerplate.
This design allows you to create errors with context-specific, type-safe fields without losing their original identity.
Key features:
* Consistent structure for logging, metrics, and APIs
* Compile-time safety for fields (DefineField[T]).
* Clean integration with the Go ecosystem (errors.Is/As, fmt, json, and slog).
* Extensible deserialization (JSON, Protobuf, etc.)
* Built-in redaction for sensitive data (Redacted[T]).
Quick example:
// Define once
var ErrNotFound = errdef.Define("not_found", errdef.HTTPStatus(404))
var UserID, _ = errdef.DefineField[string]("user_id")
// Create instances
err := ErrNotFound.With(ctx, UserID("u123")).New("user not found")
// Still works with standard `errors.Is`
errors.Is(err, ErrNotFound) // true