Artifact [8b3806e7a2]

Artifact 8b3806e7a2a42604444f5fbcbf33b413399e8136fa08918b3324db54ee5dde66:

• File leaf/agent/internal/natshdr/carrier.go — part of check-in [b53032d01f] at 2026-04-24 16:02:07 on branch trunk — notify: extract shared natshdr.Carrier to kill duplicate header-carrier

  Two copies of natsHeaderCarrier existed (leaf/agent/nats.go and leaf/agent/notify/pubsub.go), both carrying the same latent case-sensitive Get bug that was fixed in Task 6. Extract the type to leaf/agent/internal/natshdr so the next bug can be fixed once.

  While consolidating, drop the 4-tier fallback in Get in favor of a single EqualFold scan. Header maps are tiny (typically 3 entries) and tiers 1-3 were subsumed by tier 4 anyway. The new implementation is demonstrably correct and easier to read. (user: [email protected], size: 1584) [annotate] [blame] [check-ins using] [more...]

// Package natshdr provides a propagation.TextMapCarrier adapter for
// nats.Header so OpenTelemetry propagators can read/write W3C trace
// context directly on a NATS message's headers.
//
// NATS preserves header case on the send side but delivers headers
// lower-cased on the receive side, so Get is case-insensitive; otherwise
// subscribers would miss the injected "traceparent" because the wire
// delivers it as "traceparent" while http.Header.Get canonicalizes the
// lookup key to "Traceparent".
package natshdr

import (
	"net/http"
	"strings"

	"github.com/nats-io/nats.go"
	"go.opentelemetry.io/otel/propagation"
)

// Carrier adapts nats.Header to propagation.TextMapCarrier.
type Carrier nats.Header

// Get returns the first value for the header keyed by any case-variant
// of key, or "" if none is set. Header maps are tiny (typically ≤3
// entries), so an EqualFold scan is simple and demonstrably correct.
func (c Carrier) Get(key string) string {
	for k, v := range c {
		if len(v) > 0 && strings.EqualFold(k, key) {
			return v[0]
		}
	}
	return ""
}

// Set writes the canonical form so both publishers and subscribers
// converge on the same key regardless of direction.
func (c Carrier) Set(key, value string) {
	http.Header(c).Set(key, value)
}

// Keys returns the header names currently present on the carrier.
func (c Carrier) Keys() []string {
	keys := make([]string, 0, len(c))
	for k := range c {
		keys = append(keys, k)
	}
	return keys
}

// Verify Carrier implements TextMapCarrier at compile time.
var _ propagation.TextMapCarrier = Carrier(nil)