testing: fix source code location printed by testing.T

The funcr log sink must implement the new HelperLogSink
interface (otherwise the wrapper function wouldn't be handled
correctly) and also mark its own wrapper as a helper.

funcr/funcr.go

@@ -36,14 +36,21 @@ func New(fn func(prefix, args string), opts Options) logr.Logger {
 }
 
 func newSink(fn func(prefix, args string), opts Options) logr.LogSink {
-	return &fnlogger{
+	l := &fnlogger{
 		prefix:    "",
 		values:    nil,
 		depth:     0,
 		write:     fn,
 		logCaller: opts.LogCaller,
 		verbosity: opts.Verbosity,
+		helper: opts.Helper,
 	}
+	if l.helper == nil {
+		// We have to have a valid function for GetHelper, so
+		// we might as well just cover the nil case once here.
+		l.helper = func() {}
+	}
+	return l
 }
 
 // Options carries parameters which influence the way logs are generated.
@@ -55,6 +62,10 @@ type Options struct {
 	// Verbosity tells funcr which V logs to be write.  Higher values enable
 	// more logs.
 	Verbosity int
+
+	// Helper is an optional function that funcr must call to mark its own
+	// stack frames as helper functions.
+	Helper func()
 }
 
 // MessageClass indicates which category or categories of messages to consider.
@@ -72,13 +83,15 @@ type fnlogger struct {
 	values    []interface{}
 	depth     int
 	write     func(prefix, args string)
+	helper    func()
 	logCaller MessageClass
 	verbosity int
 }
 
 // Assert conformance to the interfaces.
 var _ logr.LogSink = &fnlogger{}
 var _ logr.CallDepthLogSink = &fnlogger{}
+var _ logr.HelperLogSink = &fnlogger{}
 
 func flatten(kvList ...interface{}) string {
 	if len(kvList)%2 != 0 {
@@ -271,6 +284,7 @@ func (l fnlogger) Info(level int, msg string, kvList ...interface{}) {
 	args = append(args, l.values...)
 	args = append(args, kvList...)
 	argsStr := flatten(args...)
+	l.helper()
 	l.write(l.prefix, argsStr)
 }
 
@@ -288,6 +302,7 @@ func (l fnlogger) Error(err error, msg string, kvList ...interface{}) {
 	args = append(args, l.values...)
 	args = append(args, kvList...)
 	argsStr := flatten(args...)
+	l.helper()
 	l.write(l.prefix, argsStr)
 }
 
@@ -313,3 +328,7 @@ func (l fnlogger) WithCallDepth(depth int) logr.LogSink {
 	l.depth += depth
 	return &l
 }
+
+func (l fnlogger) GetHelper() func() {
+	return l.helper
+}

testing/test.go

@@ -27,7 +27,8 @@ import (
 // Info logs are only enabled at V(0).
 func NewTestLogger(t *testing.T) logr.Logger {
 	fn := func(prefix, args string) {
+		t.Helper()
 		t.Logf("%s: %s", prefix, args)
 	}
-	return funcr.New(fn, funcr.Options{})
+	return funcr.New(fn, funcr.Options{Helper: t.Helper})
 }

testing/test_test.go

@@ -19,6 +19,8 @@ package testing
 import (
 	"fmt"
 	"testing"
+
+	"github.com/go-logr/logr"
 )
 
 func TestTestLogger(t *testing.T) {
@@ -27,4 +29,12 @@ func TestTestLogger(t *testing.T) {
 	logger.V(0).Info("V(0).info")
 	logger.V(1).Info("v(1).info")
 	logger.Error(fmt.Errorf("error"), "error")
+
+	myWrapper(logger, "hello world")
+}
+
+func myWrapper(logger logr.Logger, msg string) {
+	helper, logger := logger.Helper()
+	helper()
+	logger.Info(msg)
 }