promslog: Only log basename, not full path

Signed-off-by: Julien <roidelapluie@o11y.eu>

Author: Julien

promslog/slog.go

@@ -66,6 +66,17 @@ var (
 default:
 }
 
+return a
+}
+truncateSourceAttrFunc = func(groups []string, a slog.Attr) slog.Attr {
+if a.Key != slog.SourceKey {
+return a
+}
+
+if src, ok := a.Value.Any().(*slog.Source); ok {
+a.Value = slog.StringValue(filepath.Base(src.File) + ":" + strconv.Itoa(src.Line))
+}
+
 return a
 }
 )
@@ -165,8 +176,9 @@ func New(config *Config) *slog.Logger {
 }
 
 logHandlerOpts := &slog.HandlerOptions{
-Level: config.Level.lvl,
-AddSource: true,
+Level: config.Level.lvl,
+AddSource: true,
+ReplaceAttr: truncateSourceAttrFunc,
 }
 
 if config.Style == GoKitStyle {

promslog/slog_test.go

@@ -146,3 +146,47 @@ func TestDynamicLevels(t *testing.T) {
 })
 }
 }
+
+func TestTruncateSourceFileName_DefaultStyle(t *testing.T) {
+var buf bytes.Buffer
+
+config := &Config{
+Writer: &buf,
+}
+
+logger := New(config)
+logger.Info("test message")
+
+output := buf.String()
+
+if !strings.Contains(output, "source=slog_test.go:") {
+t.Errorf("Expected source file name to be truncated to basename, got: %s", output)
+}
+
+if strings.Contains(output, "/") {
+t.Errorf("Expected no directory separators in source file name, got: %s", output)
+}
+}
+
+func TestTruncateSourceFileName_GoKitStyle(t *testing.T) {
+var buf bytes.Buffer
+
+config := &Config{
+Writer: &buf,
+Style: GoKitStyle,
+}
+
+logger := New(config)
+logger.Info("test message")
+
+output := buf.String()
+
+// In GoKitStyle, the source key is "caller".
+if !strings.Contains(output, "caller=slog_test.go:") {
+t.Errorf("Expected caller to contain basename of source file, got: %s", output)
+}
+
+if strings.Contains(output, "/") {
+t.Errorf("Expected no directory separators in caller, got: %s", output)
+}
+}