Show invocation line for failing test

tools/rsync/api_test.go

@@ -20,7 +20,8 @@ func run_roundtrip_test(t *testing.T, src_data, changed []byte, num_of_patches,
 	using_serialization := false
 	prefix_msg := func() string {
 		q := utils.IfElse(using_serialization, "with", "without")
-		return fmt.Sprintf("Running %s serialization: src size: %d changed size: %d difference: %d\n", q, len(src_data), len(changed), len(changed)-len(src_data))
+		return fmt.Sprintf("%s: Running %s serialization: src size: %d changed size: %d difference: %d\n",
+			utils.SourceLoc(1), q, len(src_data), len(changed), len(changed)-len(src_data))
 	}
 
 	test_equal := func(src_data, output []byte) {

tools/utils/misc.go

@@ -5,7 +5,9 @@ package utils
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"reflect"
+	"runtime"
 	"strconv"
 
 	"golang.org/x/exp/constraints"
@@ -270,3 +272,25 @@ func IfElse[T any](condition bool, if_val T, else_val T) T {
 	}
 	return else_val
 }
+
+func SourceLine(skip_frames ...int) int {
+	s := 1
+	if len(skip_frames) > 0 {
+		s += skip_frames[0]
+	}
+	if _, _, ans, ok := runtime.Caller(s); ok {
+		return ans
+	}
+	return -1
+}
+
+func SourceLoc(skip_frames ...int) string {
+	s := 1
+	if len(skip_frames) > 0 {
+		s += skip_frames[0]
+	}
+	if _, file, line, ok := runtime.Caller(s); ok {
+		return filepath.Base(file) + ":" + strconv.Itoa(line)
+	}
+	return "unknown"
+}