go.opentelemetry.io/otel v1.45.0: Default global TextMapPropagator silently no-ops cross-boundary trace context injection, while Extract yields remote non-recording span contexts without activating spans and malformed baggage is silently dropped

# CSX Sample Notes: OpenTelemetry Go TextMapPropagator and Baggage Lifecycle

## Search Known Solution Result
- `search_known_solution` returned existing OpenTelemetry sample `sha256:3f14ed288a161c7b18e8a641230a1acbbe95a6630bf2bfe7bf77cc02b2958d34` (*"Unwired OpenTelemetry tracers silently emit invalid zero-context spans while batch-buffered tracers drop spans without explicit flush or shutdown"*).
- **Why this sample is distinct**: This sample targets distributed context propagation and baggage extraction across process boundaries (`go.opentelemetry.io/otel/propagation` and `go.opentelemetry.io/otel/baggage`). It proves that `otel.GetTextMapPropagator()` defaults to a silent no-op propagator with 0 fields, that `Extract()` only attaches a non-recording remote `SpanContext` rather than starting an active child span, that unencoded baggage values are rejected on construction but silently dropped on header extraction without error, and that duplicate baggage keys follow last-value-wins precedence.

## What a Model Would Have Written Instead
A model would assume `otel.GetTextMapPropagator()` has W3C `TraceContext` and `Baggage` enabled by default, expect `Extract()` to activate a recording span directly in `context.Context`, and assume malformed or duplicate baggage headers trigger runtime errors or preserve earlier keys.

## How the Wrong Version Fails
It fails silently with a green build: HTTP/RPC handlers compile and execute normally without errors or panics, but cross-service `traceparent` and `baggage` headers are completely omitted on outbound calls, incoming trace contexts remain disconnected/non-recording, and malformed baggage members vanish silently without warning.

{"case":{"caseId":"case:sha256:69824c393b5aa6327151fc6f6bcdff2a38ef162aa87ff32199b5739cf5302283","contract":["assert default global TextMapPropagator has 0 fields and silently no-ops on Extract and Inject","assert composite propagator extracts remote SpanContext and baggage into context","assert extracted context holds non-recording span until explicitly started with Tracer","assert child span started from remote context inherits TraceID with new local SpanID","assert unencoded baggage whitespace returns error on construction but is silently dropped on carrier extraction","assert duplicate baggage keys resolve via last-value-wins precedence during extraction and creation"],"goal":"Default global TextMapPropagator silently no-ops cross-boundary trace context injection, while Extract yields remote non-recording span contexts without activating spans and malformed baggage is silently dropped","kind":"HOW","packages":["pkg:golang/go.opentelemetry.io/otel@v1.45.0","pkg:golang/go.opentelemetry.io/otel/sdk@v1.45.0","pkg:golang/go.opentelemetry.io/otel/trace@v1.45.0"],"schemaVersion":1,"symbols":["go.opentelemetry.io/otel.GetTextMapPropagator","go.opentelemetry.io/otel/propagation.NewCompositeTextMapPropagator","go.opentelemetry.io/otel/propagation.TraceContext","go.opentelemetry.io/otel/propagation.Baggage","go.opentelemetry.io/otel/baggage.NewMember","go.opentelemetry.io/otel/baggage.New","go.opentelemetry.io/otel/trace.SpanContextFromContext"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","ecosystem":"golang","executionContext":"go","language":"go","os":"linux","packageManager":"gomod","runtime":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/go.opentelemetry.io/otel@v1.45.0","pkg:golang/go.opentelemetry.io/otel/sdk@v1.45.0","pkg:golang/go.opentelemetry.io/otel/trace@v1.45.0"],"schemaVersion":1,"symbols":["go.opentelemetry.io/otel.GetTextMapPropagator","go.opentelemetry.io/otel/propagation.NewCompositeTextMapPropagator","go.opentelemetry.io/otel/propagation.TraceContext","go.opentelemetry.io/otel/propagation.Baggage","go.opentelemetry.io/otel/baggage.NewMember","go.opentelemetry.io/otel/baggage.New","go.opentelemetry.io/otel/trace.SpanContextFromContext"],"verifierAdapter":"golang@1"}

module sample

go 1.26.5

require (
	go.opentelemetry.io/otel v1.45.0
	go.opentelemetry.io/otel/sdk v1.45.0
	go.opentelemetry.io/otel/trace v1.45.0
)

require (
	github.com/cespare/xxhash/v2 v2.3.0 // indirect
	github.com/go-logr/logr v1.4.4 // indirect
	github.com/go-logr/stdr v1.2.2 // indirect
	github.com/google/uuid v1.6.0 // indirect
	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
	go.opentelemetry.io/otel/metric v1.45.0 // indirect
	golang.org/x/sys v0.47.0 // indirect
)

github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
github.com/go-logr/logr v1.4.4 h1:tG4xh9yMsRCAiodLVTxyrkzSZ9+o0L1Kg/+cPVcbP/8=
github.com/go-logr/logr v1.4.4/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
go.opentelemetry.io/otel v1.45.0 h1:pdrWmLHofpubmArBv1LgFSv1Z0Ie/ppdZzu+kUN5EeU=
go.opentelemetry.io/otel v1.45.0/go.mod h1:XZxIqPapzEYnhNSScF5DIqXhm/rYi0FzCe2XddAwZfQ=
go.opentelemetry.io/otel/metric v1.45.0 h1:7Eg1uH7CJ5cXv9is6tnBe1FI6rj1nwUdbFypRm3br/M=
go.opentelemetry.io/otel/metric v1.45.0/go.mod h1:HAPbm1nd3p1PmFH7v2dR+6BjXxw+Lq4a2+pndMAm08s=
go.opentelemetry.io/otel/sdk v1.45.0 h1:4VVSMgQ83dUgW2aoX5f6JgLvHwIvzcuLnF9lUdCSpCw=
go.opentelemetry.io/otel/sdk v1.45.0/go.mod h1:Sr40LgXV7DsKMMJMKOhUWOgMWTfAaqvm2kF0g7ilwuA=
go.opentelemetry.io/otel/sdk/metric v1.45.0 h1:oVFszMfyj1Am6s24Vtc7wBb8BKLcwepJjNEYILuiE3o=
go.opentelemetry.io/otel/sdk/metric v1.45.0/go.mod h1:vUWUxDZvu1WVRj8JA8S0AdhsPrZoDpA2DdZauIh4mDA=
go.opentelemetry.io/otel/trace v1.45.0 h1:l/mP6Uv7oNO7/TblbhpbgMidxhq1uO/rPsikOyVhxag=
go.opentelemetry.io/otel/trace v1.45.0/go.mod h1:qoJJA2xNMnxRrdISU/kLtfUH2wNeQbiv+jhs/CxI8bc=
go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package sample_test

import (
	"context"
	"net/url"
	"sort"
	"testing"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/baggage"
	"go.opentelemetry.io/otel/propagation"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
	"go.opentelemetry.io/otel/trace"
)

func TestDefaultPropagatorSilentNoOp(t *testing.T) {
	ctx := context.Background()

	// Setup a carrier with valid W3C traceparent and baggage headers
	incomingCarrier := propagation.MapCarrier{
		"traceparent": "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01",
		"baggage":     "user_id=usr_99,role=admin",
	}

	// Trap 1: A naive model expects otel.GetTextMapPropagator() to have W3C propagators enabled by default.
	// In reality, the default global propagator is a no-op that silently ignores incoming headers.
	defaultProp := otel.GetTextMapPropagator()
	if fields := defaultProp.Fields(); len(fields) != 0 {
		t.Errorf("default TextMapPropagator must have 0 fields, got %v", fields)
	}

	extractedCtx := defaultProp.Extract(ctx, incomingCarrier)

	// Extracted SpanContext remains completely invalid (all zeroes)
	sc := trace.SpanContextFromContext(extractedCtx)
	if sc.IsValid() {
		t.Errorf("default propagator must NOT extract valid SpanContext without registration")
	}

	// Extracted Baggage remains empty
	bg := baggage.FromContext(extractedCtx)
	if bg.Len() != 0 {
		t.Errorf("default propagator must NOT extract Baggage without registration, got len %d", bg.Len())
	}

	// Trap 2: Outgoing Inject with default propagator silently does nothing to outgoing carrier.
	mem, err := baggage.NewMember("req_id", "req_123")
	if err != nil {
		t.Fatalf("failed to create baggage member: %v", err)
	}
	bgWithReq, err := baggage.New(mem)
	if err != nil {
		t.Fatalf("failed to create baggage: %v", err)
	}
	outgoingCtx := baggage.ContextWithBaggage(ctx, bgWithReq)

	outgoingCarrier := propagation.MapCarrier{}
	defaultProp.Inject(outgoingCtx, outgoingCarrier)
	if len(outgoingCarrier) != 0 {
		t.Errorf("default propagator Inject must not write headers, got %v", outgoingCarrier)
	}
}

func TestCompositePropagatorAndRemoteSpanState(t *testing.T) {
	ctx := context.Background()

	// Configure composite propagator with TraceContext and Baggage
	composite := propagation.NewCompositeTextMapPropagator(
		propagation.TraceContext{},
		propagation.Baggage{},
	)

	fields := composite.Fields()
	sort.Strings(fields)
	expectedFields := []string{"baggage", "traceparent", "tracestate"}
	if len(fields) != 3 || fields[0] != expectedFields[0] || fields[1] != expectedFields[1] || fields[2] != expectedFields[2] {
		t.Fatalf("expected fields %v, got %v", expectedFields, fields)
	}

	incomingCarrier := propagation.MapCarrier{
		"traceparent": "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01",
		"baggage":     "tenant_id=corp_42",
	}

	extractedCtx := composite.Extract(ctx, incomingCarrier)

	// Trap 3: Extract populates remote SpanContext, but does NOT start a recording span!
	// SpanFromContext returns a non-recording placeholder span.
	remoteSC := trace.SpanContextFromContext(extractedCtx)
	if !remoteSC.IsValid() {
		t.Fatalf("expected valid remote SpanContext")
	}
	if !remoteSC.IsRemote() {
		t.Errorf("extracted SpanContext must be marked as Remote")
	}
	if remoteSC.TraceID().String() != "4bf92f3577b34da6a3ce929d0e0e4736" {
		t.Errorf("unexpected TraceID: %s", remoteSC.TraceID().String())
	}
	if remoteSC.SpanID().String() != "00f067aa0ba902b7" {
		t.Errorf("unexpected SpanID: %s", remoteSC.SpanID().String())
	}

	spanFromCtx := trace.SpanFromContext(extractedCtx)
	if spanFromCtx.IsRecording() {
		t.Errorf("span from extracted context must NOT be recording before Tracer.Start")
	}

	// Baggage is extracted into context
	bg := baggage.FromContext(extractedCtx)
	if bg.Len() != 1 || bg.Member("tenant_id").Value() != "corp_42" {
		t.Errorf("baggage tenant_id not extracted properly")
	}

	// Trap 4: Spawning an actual child span with a configured SDK TracerProvider
	exporter := tracetest.NewInMemoryExporter()
	tp := sdktrace.NewTracerProvider(sdktrace.WithSyncer(exporter))
	defer func() {
		_ = tp.Shutdown(ctx)
	}()

	tracer := tp.Tracer("http-handler")
	childCtx, childSpan := tracer.Start(extractedCtx, "handle-request")

	if !childSpan.IsRecording() {
		t.Errorf("child span created from SDK tracer must be recording")
	}
	childSC := childSpan.SpanContext()
	if childSC.IsRemote() {
		t.Errorf("new local child span must NOT be remote")
	}
	// Child inherits parent TraceID but generates a new distinct SpanID
	if childSC.TraceID() != remoteSC.TraceID() {
		t.Errorf("child TraceID must match parent TraceID")
	}
	if childSC.SpanID() == remoteSC.SpanID() {
		t.Errorf("child SpanID must NOT equal remote parent SpanID")
	}

	// Trap 5: Injecting child context into outgoing downstream carrier
	downstreamCarrier := propagation.MapCarrier{}
	composite.Inject(childCtx, downstreamCarrier)

	expectedPrefix := "00-" + remoteSC.TraceID().String() + "-" + childSC.SpanID().String() + "-01"
	if downstreamCarrier.Get("traceparent") != expectedPrefix {
		t.Errorf("downstream traceparent expected %s, got %s", expectedPrefix, downstreamCarrier.Get("traceparent"))
	}
	if downstreamCarrier.Get("baggage") != "tenant_id=corp_42" {
		t.Errorf("downstream baggage expected tenant_id=corp_42, got %s", downstreamCarrier.Get("baggage"))
	}

	childSpan.End()
}

func TestBaggageValidationAndSilentDropping(t *testing.T) {
	ctx := context.Background()
	bagProp := propagation.Baggage{}

	// Trap 6: Baggage key and value syntax rules per W3C specification.
	// Keys must be RFC 7230 tokens (no spaces or delimiters).
	// Values containing spaces or disallowed delimiters must be percent-encoded upon creation,
	// and Member.Value() holds the decoded value.
	_, errInvalidKey := baggage.NewMember("invalid key", "val")
	if errInvalidKey == nil {
		t.Errorf("baggage.NewMember must fail on key with whitespace")
	}

	_, errInvalidVal := baggage.NewMember("key", "val with spaces")
	if errInvalidVal == nil {
		t.Errorf("baggage.NewMember must fail on raw unencoded whitespace in value")
	}

	encodedVal := url.PathEscape("val with spaces")
	validMem, errValid := baggage.NewMember("valid_key", encodedVal)
	if errValid != nil {
		t.Fatalf("baggage.NewMember failed with percent-encoded value: %v", errValid)
	}
	if validMem.Value() != "val with spaces" {
		t.Errorf("expected decoded member value 'val with spaces', got %s", validMem.Value())
	}
	if validMem.String() != "valid_key=val%20with%20spaces" {
		t.Errorf("expected member string 'valid_key=val%%20with%%20spaces', got %s", validMem.String())
	}

	// Trap 7: When extracting from carrier, malformed baggage headers are silently discarded
	// without raising error or panic, because Extract has no error return path.
	carrierWithMalformed := propagation.MapCarrier{
		"baggage": "invalid key=bad,good_key=good_val,broken=val with spaces",
	}

	extractedCtx := bagProp.Extract(ctx, carrierWithMalformed)
	bg := baggage.FromContext(extractedCtx)

	// Only 'good_key' survives; malformed entries are silently omitted
	if bg.Len() != 1 {
		t.Fatalf("expected exactly 1 valid baggage entry, got %d", bg.Len())
	}
	if bg.Member("good_key").Value() != "good_val" {
		t.Errorf("expected good_key=good_val, got %s", bg.Member("good_key").Value())
	}
	if bg.Member("invalid key").Value() != "" {
		t.Errorf("invalid key should not be present in baggage")
	}
}

func TestBaggageDuplicateKeyLastValueWins(t *testing.T) {
	ctx := context.Background()
	bagProp := propagation.Baggage{}

	// Trap 8: Duplicate keys in baggage header follow 'last-value-wins' semantics in OpenTelemetry Go.
	carrierWithDuplicates := propagation.MapCarrier{
		"baggage": "session_id=111,session_id=222,session_id=333",
	}

	extractedCtx := bagProp.Extract(ctx, carrierWithDuplicates)
	bg := baggage.FromContext(extractedCtx)

	if bg.Len() != 1 {
		t.Fatalf("expected 1 deduplicated baggage entry, got %d", bg.Len())
	}
	if bg.Member("session_id").Value() != "333" {
		t.Errorf("expected session_id=333 (last value wins), got %s", bg.Member("session_id").Value())
	}

	// Also in programmatic baggage.New(m1, m2): last member takes precedence
	m1, _ := baggage.NewMember("key", "first")
	m2, _ := baggage.NewMember("key", "second")
	bgProgrammatic, err := baggage.New(m1, m2)
	if err != nil {
		t.Fatalf("baggage.New failed: %v", err)
	}
	if bgProgrammatic.Member("key").Value() != "second" {
		t.Errorf("expected programmatic duplicate key to take last value 'second', got %s", bgProgrammatic.Member("key").Value())
	}
}