envcar: normalize cached environment variable names

CHANGELOG.md

@@ -22,6 +22,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Changed
 
 - Prepend `_` to the normalized environment variable name when the key starts with a digit in `go.opentelemetry.io/contrib/propagators/envcar`, ensuring POSIX compliance. (#8678)
+- Normalize cached environment variable names in `go.opentelemetry.io/contrib/propagators/envcar`, aligning `Carrier.Keys` output with the carrier's normalized key format. (#8761)
 
 ### Fixed
 

propagators/envcar/carrier.go

@@ -12,7 +12,7 @@ import (
 )
 
 // Carrier is a TextMapCarrier that uses the environment variables as a
-// storage medium for propagated key-value pairs. The keys are normalised
+// storage medium for propagated key-value pairs. The keys are normalized
 // before being used to access the environment variables.
 // This is useful for propagating values that are set in the environment
 // and need to be accessed by different processes or services.
@@ -43,7 +43,8 @@ func (c *Carrier) fetch() {
 		c.values = make(map[string]string, len(environ))
 		for _, kv := range environ {
 			kvPair := strings.SplitN(kv, "=", 2)
-			c.values[kvPair[0]] = kvPair[1]
+			key := normalize(kvPair[0])
+			c.values[key] = kvPair[1]
 		}
 	})
 }
@@ -74,8 +75,7 @@ func (c *Carrier) Set(key, value string) {
 // The first call to [Carrier.Get] or [Carrier.Keys] for a
 // given Carrier will read and store the values from the
 // environment and all future reads will be from that store.
-// Keys are returned as is, without any normalization, but
-// this behavior is subject to change.
+// The keys are returned in their normalized form.
 func (c *Carrier) Keys() []string {
 	c.fetch()
 	keys := make([]string, 0, len(c.values))

propagators/envcar/carrier_test.go

@@ -61,6 +61,19 @@ func TestExtractValidTraceContextEnvCarrier(t *testing.T) {
 				Remote:     true,
 			}),
 		},
+		{
+			name: "lowercase env names",
+			envs: map[string]string{
+				"traceparent": "00-000000000000007b00000000000001c8-000000000000007b-00",
+				"tracestate":  stateStr,
+			},
+			want: trace.NewSpanContext(trace.SpanContextConfig{
+				TraceID:    traceID,
+				SpanID:     spanID,
+				TraceState: state,
+				Remote:     true,
+			}),
+		},
 	}
 
 	for _, tc := range tests {
@@ -134,21 +147,22 @@ func TestInjectTraceContextEnvCarrier(t *testing.T) {
 }
 
 func TestCarrierKeys(t *testing.T) {
-	t.Setenv("TRACEPARENT", "value")
+	t.Setenv("traceparent", "value")
 
 	c := envcar.Carrier{}
 	keys := c.Keys()
 
 	assert.Contains(t, keys, "TRACEPARENT")
+	assert.NotContains(t, keys, "traceparent")
 }
 
 func TestCarrierSetNilFunc(_ *testing.T) {
 	c := envcar.Carrier{} // SetEnvFunc is nil
 	c.Set("key", "value") // should not panic, just no-op
 }
 
-func TestCarrierGetCaseInsensitive(t *testing.T) {
-	t.Setenv("TRACEPARENT", "myvalue")
+func TestCarrierGetNormalizesKey(t *testing.T) {
+	t.Setenv("traceparent", "myvalue")
 
 	c := envcar.Carrier{}
 	assert.Equal(t, "myvalue", c.Get("traceparent"))