contextual logging: enable by default again

klog.go

@@ -549,7 +549,11 @@ type loggingT struct {
 	vmap map[uintptr]Level
 }
 
-var logging loggingT
+var logging = loggingT{
+	settings: settings{
+		contextualLoggingEnabled: true,
+	},
+}
 
 // setVState sets a consistent state for V logging.
 // l.mu is held.

ktesting/contextual_test.go

@@ -0,0 +1,56 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+Copyright 2020 Intel Coporation.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package ktesting_test
+
+import (
+	"context"
+	"testing"
+
+	"k8s.io/klog/v2"
+	"k8s.io/klog/v2/ktesting"
+)
+
+func TestContextual(t *testing.T) {
+	logger, ctx := ktesting.NewTestContext(t)
+
+	doSomething(ctx)
+
+	// When contextual logging is disabled, the output goes to klog
+	// instead of the testing logger.
+	state := klog.CaptureState()
+	defer state.Restore()
+	klog.EnableContextualLogging(false)
+	doSomething(ctx)
+
+	testingLogger, ok := logger.GetSink().(ktesting.Underlier)
+	if !ok {
+		t.Fatal("Should have had a ktesting LogSink!?")
+	}
+
+	actual := testingLogger.GetBuffer().String()
+	expected := `INFO hello world
+INFO foo: hello also from me
+`
+	if actual != expected {
+		t.Errorf("mismatch in captured output, expected:\n%s\ngot:\n%s\n", expected, actual)
+	}
+}
+
+func doSomething(ctx context.Context) {
+	logger := klog.FromContext(ctx)
+	logger.Info("hello world")
+
+	logger = logger.WithName("foo")
+	ctx = klog.NewContext(ctx, logger)
+	doSomeMore(ctx)
+}
+
+func doSomeMore(ctx context.Context) {
+	logger := klog.FromContext(ctx)
+	logger.Info("hello also from me")
+}