testing: fix source code location printed by testing.T

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

funcr/funcr.go

@@ -46,15 +46,22 @@ type Underlier interface {
 }
 
 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,
 		logTimestamp: opts.LogTimestamp,
 		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.
@@ -70,6 +77,10 @@ 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 will call to mark its own
+	// stack frames as helper functions.
+	Helper func()
 }
 
 // MessageClass indicates which category or categories of messages to consider.
@@ -89,6 +100,7 @@ type fnlogger struct {
 	values       []interface{}
 	depth        int
 	write        func(prefix, args string)
+	helper       func()
 	logCaller    MessageClass
 	logTimestamp bool
 	verbosity    int
@@ -98,6 +110,7 @@ type fnlogger struct {
 var _ logr.LogSink = &fnlogger{}
 var _ logr.CallDepthLogSink = &fnlogger{}
 var _ Underlier = &fnlogger{}
+var _ logr.CallStackHelperLogSink = &fnlogger{}
 
 func flatten(kvList ...interface{}) string {
 	if len(kvList)%2 != 0 {
@@ -293,6 +306,7 @@ 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)
 }
 
@@ -313,6 +327,7 @@ 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)
 }
 
@@ -342,3 +357,7 @@ func (l fnlogger) WithCallDepth(depth int) logr.LogSink {
 func (l fnlogger) GetUnderlying() func(prefix, args string) {
 	return l.write
 }
+
+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

@@ -19,12 +19,27 @@ package testing
 import (
 	"fmt"
 	"testing"
+
+	"github.com/go-logr/logr"
 )
 
 func TestTestLogger(t *testing.T) {
-	logger := NewTestLogger(t)
-	logger.Info("info")
-	logger.V(0).Info("V(0).info")
-	logger.V(1).Info("v(1).info")
-	logger.Error(fmt.Errorf("error"), "error")
+	log := NewTestLogger(t)
+	log.Info("info")
+	log.V(0).Info("V(0).info")
+	log.V(1).Info("v(1).info")
+	log.Error(fmt.Errorf("error"), "error")
+	Helper(log, "hello world")
+}
+
+func Helper(log logr.Logger, msg string) {
+	helper, log := log.Helper()
+	helper()
+	helper2(log, msg)
+}
+
+func helper2(log logr.Logger, msg string) {
+	helper, log := log.Helper()
+	helper()
+	log.Info(msg)
 }