kubernetes · PersistentJZH · Jul 25, 2025 · Aug 9, 2025
diff --git a/staging/src/k8s.io/component-base/featuregate/feature_gate.go b/staging/src/k8s.io/component-base/featuregate/feature_gate.go
@@ -165,6 +165,7 @@ type MutableVersionedFeatureGate interface {
 	// Otherwise, the emulationVersion will be the same as the binary version.
 	// If set, the feature defaults and availability will be as if the binary is at the emulated version.
 	SetEmulationVersion(emulationVersion *version.Version) error
+
 	// GetAll returns a copy of the map of known feature names to versioned feature specs.
 	GetAllVersioned() map[Feature]VersionedSpecs
 	// AddVersioned adds versioned feature specs to the featureGate.
@@ -543,6 +544,16 @@ func (f *featureGate) GetAllVersioned() map[Feature]VersionedSpecs {
 }
 
 func (f *featureGate) SetEmulationVersion(emulationVersion *version.Version) error {
+	return f.setEmulationVersionWithContext(context.Background(), emulationVersion)
+}
+
+// SetEmulationVersionWithContext allows passing a context for test logger support.
+// This is primarily intended for testing scenarios.
+func (f *featureGate) SetEmulationVersionWithContext(ctx context.Context, emulationVersion *version.Version) error {
+	return f.setEmulationVersionWithContext(ctx, emulationVersion)
+}
+
+func (f *featureGate) setEmulationVersionWithContext(ctx context.Context, emulationVersion *version.Version) error {
 	if emulationVersion.EqualTo(f.EmulationVersion()) {
 		return nil
 	}
@@ -561,11 +572,19 @@ func (f *featureGate) SetEmulationVersion(emulationVersion *version.Version) err
 
 	queriedFeatures := f.queriedFeatures.Load().(sets.Set[Feature])
 	known := f.known.Load().(map[Feature]VersionedSpecs)
+	contextLogger := getContextLogger(ctx)
+
 	for feature := range queriedFeatures {
 		newVal := featureEnabled(feature, enabled, known, emulationVersion)
 		oldVal := featureEnabled(feature, f.enabled.Load().(map[Feature]bool), known, f.EmulationVersion())
 		if newVal != oldVal {
-			klog.Warningf("SetEmulationVersion will change already queried feature:%s from %v to %v", feature, oldVal, newVal)
+			warningMsg := fmt.Sprintf("SetEmulationVersion will change already queried feature:%s from %v to %v", feature, oldVal, newVal)
+			// Try to log to context logger first, fallback to global klog
+			if contextLogger != nil {
+				contextLogger.Logf("WARNING: %s", warningMsg)
+			} else {
+				klog.Warningf("%s", warningMsg)
+			}
 		}
 	}
 
@@ -669,6 +688,32 @@ func (f *featureGate) AddMetrics() {
 	}
 }
 
+// testLoggerKey is used to store test logger in context
+type testLoggerKey struct{}
+
+// WithTestLoggerContext returns a context with test logger for redirecting warnings to test output
+func WithTestLoggerContext(ctx context.Context, logger interface {
+	Logf(format string, args ...interface{})
+}) context.Context {
+	return context.WithValue(ctx, testLoggerKey{}, logger)
+}
+
+// getContextLogger retrieves logger from context if available
+func getContextLogger(ctx context.Context) interface {
+	Logf(format string, args ...interface{})
+} {
+	if ctx == nil {
+		return nil
+	}
+	logger, ok := ctx.Value(testLoggerKey{}).(interface {
+		Logf(format string, args ...interface{})
+	})
+	if ok {
+		return logger
+	}
+	return nil
+}
+
 // KnownFeatures returns a slice of strings describing the FeatureGate's known features.
 // preAlpha, Deprecated and GA features are hidden from the list.
 func (f *featureGate) KnownFeatures() []string {

diff --git a/staging/src/k8s.io/component-base/featuregate/testing/feature_gate.go b/staging/src/k8s.io/component-base/featuregate/testing/feature_gate.go
@@ -17,6 +17,7 @@ limitations under the License.
 package testing
 
 import (
+	"context"
 	"fmt"
 	"strings"
 	"sync"
@@ -124,18 +125,37 @@ func SetFeatureGateEmulationVersionDuringTest(tb TB, gate featuregate.FeatureGat
 	tb.Helper()
 	detectParallelOverrideCleanup := detectParallelOverrideEmulationVersion(tb, ver)
 	originalEmuVer := gate.(featuregate.MutableVersionedFeatureGate).EmulationVersion()
-	if err := gate.(featuregate.MutableVersionedFeatureGate).SetEmulationVersion(ver); err != nil {
+
+	if err := setEmulationVersionForTest(gate.(featuregate.MutableVersionedFeatureGate), ver, tb); err != nil {
 		tb.Fatalf("failed to set emulation version to %s during test: %v", ver.String(), err)
 	}
 	tb.Cleanup(func() {
 		tb.Helper()
 		detectParallelOverrideCleanup()
-		if err := gate.(featuregate.MutableVersionedFeatureGate).SetEmulationVersion(originalEmuVer); err != nil {
+		if err := setEmulationVersionForTest(gate.(featuregate.MutableVersionedFeatureGate), originalEmuVer, tb); err != nil {
 			tb.Fatalf("failed to restore emulation version to %s during test", originalEmuVer.String())
 		}
 	})
 }
 
+// setEmulationVersionForTest sets emulation version with test-friendly warning handling.
+// This uses context to redirect warnings to test output.
+func setEmulationVersionForTest(gate featuregate.MutableVersionedFeatureGate, ver *version.Version, tb TB) error {
+	// Check if this gate supports context-aware emulation version setting
+	type contextAwareGate interface {
+		SetEmulationVersionWithContext(ctx context.Context, emulationVersion *version.Version) error
+	}
+
+	if contextGate, ok := gate.(contextAwareGate); ok {
+		// Use context with test logger to redirect warnings to test output
+		ctx := featuregate.WithTestLoggerContext(context.Background(), tb)
+		return contextGate.SetEmulationVersionWithContext(ctx, ver)
+	}
+
+	// Fallback to regular method for implementations that don't support context
+	return gate.SetEmulationVersion(ver)
+}
+
 func detectParallelOverride(tb TB, f featuregate.Feature) func() {
 	tb.Helper()
 	overrideLock.Lock()
@@ -196,5 +216,6 @@ type TB interface {
 	Fatal(args ...any)
 	Fatalf(format string, args ...any)
 	Helper()
+	Logf(format string, args ...interface{})
 	Name() string
 }