add SetSlogLogger

This is syntactic sugar, but it's still useful because it hides logr from developers who only care about klog and slog.

Author: pohly

contextual_slog.go

@@ -0,0 +1,31 @@
+//go:build go1.21
+// +build go1.21
+
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package klog
+
+import (
+"log/slog"
+
+"github.com/go-logr/logr"
+)
+
+// SetSlogLogger reconfigures klog to log through the slog logger. The logger must not be nil.
+func SetSlogLogger(logger *slog.Logger) {
+SetLoggerWithOptions(logr.FromSlogHandler(logger.Handler()), ContextualLogger(true))
+}

contextual_slog_example_test.go

@@ -0,0 +1,48 @@
+//go:build go1.21
+// +build go1.21
+
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package klog_test
+
+import (
+"log/slog"
+"os"
+
+"k8s.io/klog/v2"
+)
+
+func ExampleSetSlogLogger() {
+state := klog.CaptureState()
+defer state.Restore()
+
+handler := slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+if a.Key == slog.TimeKey {
+// Avoid non-deterministic output.
+return slog.Attr{}
+}
+return a
+},
+})
+logger := slog.New(handler)
+klog.SetSlogLogger(logger)
+klog.Info("hello world")
+
+// Output:
+// level=INFO msg="hello world"
+}