logging: support call depth via logr, structured logging

The new releases of klog (via klogr) and logr expose support for call
traces via a new WithCallDepth API in logr.

The new klogr can be configured to pass structured log entries into
klog instead of turning them into a single text message.

vendor/github.com/go-logr/logr/discard.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2020 The logr 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 logr
+
+// Discard returns a valid Logger that discards all messages logged to it.
+// It can be used whenever the caller is not interested in the logs.
+func Discard() Logger {
+	return DiscardLogger{}
+}
+
+// DiscardLogger is a Logger that discards all messages.
+type DiscardLogger struct{}
+
+func (l DiscardLogger) Enabled() bool {
+	return false
+}
+
+func (l DiscardLogger) Info(msg string, keysAndValues ...interface{}) {
+}
+
+func (l DiscardLogger) Error(err error, msg string, keysAndValues ...interface{}) {
+}
+
+func (l DiscardLogger) V(level int) Logger {
+	return l
+}
+
+func (l DiscardLogger) WithValues(keysAndValues ...interface{}) Logger {
+	return l
+}
+
+func (l DiscardLogger) WithName(name string) Logger {
+	return l
+}
+
+// Verify that it actually implements the interface
+var _ Logger = DiscardLogger{}