Fix baggage.NewMember to decode the accepted value

CHANGELOG.md

@@ -8,6 +8,9 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Fixed
+- Fix function `baggage.NewMember` to decode the `value` parameter instead of directly use it according to the W3C specification. (#3144)
+
 ### Added
 
 - The metric portion of the OpenCensus bridge (`go.opentelemetry.io/otel/bridge/opencensus`) has been reintroduced. (#3192)

baggage/baggage.go

@@ -263,7 +263,15 @@ func NewMember(key, value string, props ...Property) (Member, error) {
 	if err := m.validate(); err != nil {
 		return newInvalidMember(), err
 	}
-
+	// the accepted value of this function should be decoded
+	// according to the W3C Baggage value specification
+	// e.g. value "%3B" should be treated as its decoded form ";"
+	decodedValue, err := url.QueryUnescape(value)
+	if err != nil {
+		return newInvalidMember(),
+			fmt.Errorf("%w: %q", errInvalidValue, value)
+	}
+	m.value = decodedValue
 	return m, nil
 }
 

baggage/baggage_test.go

@@ -768,6 +768,23 @@ func TestNewMember(t *testing.T) {
 	}
 	assert.Equal(t, expected, m)
 
+	// wrong value with wrong decoding
+	val = "%zzzzz"
+	_, err = NewMember(key, val, p)
+	assert.ErrorIs(t, err, errInvalidValue)
+
+	// value should be decoded
+	val = "%3B"
+	m, err = NewMember(key, val, p)
+	expected = Member{
+		key:        key,
+		value:      ";",
+		properties: properties{{key: "foo", hasData: true}},
+		hasData:    true,
+	}
+	assert.NoError(t, err)
+	assert.Equal(t, expected, m)
+
 	// Ensure new member is immutable.
 	p.key = "bar"
 	assert.Equal(t, expected, m)
@@ -784,6 +801,17 @@ func TestPropertiesValidate(t *testing.T) {
 	assert.NoError(t, p.validate())
 }
 
+func TestMemberString(t *testing.T) {
+	// normal key value pair
+	member, _ := NewMember("key", "value")
+	memberStr := member.String()
+	assert.Equal(t, memberStr, "key=value")
+	// encoded key
+	member, _ = NewMember("key", "%3B")
+	memberStr = member.String()
+	assert.Equal(t, memberStr, "key=%3B")
+}
+
 var benchBaggage Baggage
 
 func BenchmarkNew(b *testing.B) {

propagation/baggage_test.go

@@ -17,6 +17,7 @@ package propagation_test
 import (
 	"context"
 	"net/http"
+	"net/url"
 	"strings"
 	"testing"
 
@@ -46,8 +47,8 @@ func (m member) Member(t *testing.T) baggage.Member {
 		}
 		props = append(props, p)
 	}
-
-	bMember, err := baggage.NewMember(m.Key, m.Value, props...)
+	// when creating a new Member, NewMember only accepted encoded string as value
+	bMember, err := baggage.NewMember(m.Key, url.QueryEscape(m.Value), props...)
 	if err != nil {
 		t.Fatal(err)
 	}