log: default JSON log handler should log all verbosity levels (#29471)

Co-authored-by: lightclient <[email protected]>

Author: Roberto Bayardo

internal/debug/flags.go

@@ -231,9 +231,9 @@ func Setup(ctx *cli.Context) error {
 	case ctx.Bool(logjsonFlag.Name):
 		// Retain backwards compatibility with `--log.json` flag if `--log.format` not set
 		defer log.Warn("The flag '--log.json' is deprecated, please use '--log.format=json' instead")
-		handler = log.JSONHandler(output)
+		handler = log.JSONHandlerWithLevel(output, log.LevelInfo)
 	case logFmtFlag == "json":
-		handler = log.JSONHandler(output)
+		handler = log.JSONHandlerWithLevel(output, log.LevelInfo)
 	case logFmtFlag == "logfmt":
 		handler = log.LogfmtHandler(output)
 	case logFmtFlag == "", logFmtFlag == "terminal":

log/handler.go

@@ -115,8 +115,15 @@ func (l *leveler) Level() slog.Level {
 
 // JSONHandler returns a handler which prints records in JSON format.
 func JSONHandler(wr io.Writer) slog.Handler {
+	return JSONHandlerWithLevel(wr, levelMaxVerbosity)
+}
+
+// JSONHandler returns a handler which prints records in JSON format that are less than or equal to
+// the specified verbosity level.
+func JSONHandlerWithLevel(wr io.Writer, level slog.Level) slog.Handler {
 	return slog.NewJSONHandler(wr, &slog.HandlerOptions{
 		ReplaceAttr: builtinReplaceJSON,
+		Level:       &leveler{level},
 	})
 }
 

log/logger_test.go

@@ -50,6 +50,25 @@ func TestTerminalHandlerWithAttrs(t *testing.T) {
 	}
 }
 
+// Make sure the default json handler outputs debug log lines
+func TestJSONHandler(t *testing.T) {
+	out := new(bytes.Buffer)
+	handler := JSONHandler(out)
+	logger := slog.New(handler)
+	logger.Debug("hi there")
+	if len(out.String()) == 0 {
+		t.Error("expected non-empty debug log output from default JSON Handler")
+	}
+
+	out.Reset()
+	handler = JSONHandlerWithLevel(out, slog.LevelInfo)
+	logger = slog.New(handler)
+	logger.Debug("hi there")
+	if len(out.String()) != 0 {
+		t.Errorf("expected empty debug log output, but got: %v", out.String())
+	}
+}
+
 func BenchmarkTraceLogging(b *testing.B) {
 	SetDefault(NewLogger(NewTerminalHandler(os.Stderr, true)))
 	b.ResetTimer()