From 39676004def5d3cffcff2323d5af02992a4e97cd Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Thu, 3 Nov 2022 20:50:28 -0500
Subject: [PATCH] Fix logger string truncation with UTF-8

fixes #1365
---
 tracelog/tracelog.go      | 10 +++++++++-
 tracelog/tracelog_test.go | 42 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/tracelog/tracelog.go b/tracelog/tracelog.go
index d51b9b95..7b19f343 100644
--- a/tracelog/tracelog.go
+++ b/tracelog/tracelog.go
@@ -7,6 +7,7 @@ import (
 	"errors"
 	"fmt"
 	"time"
+	"unicode/utf8"
 
 	"github.com/jackc/pgx/v5"
 )
@@ -62,6 +63,7 @@ func (f LoggerFunc) Log(ctx context.Context, level LogLevel, msg string, data ma
 // LogLevelFromString converts log level string to constant
 //
 // Valid levels:
+//
 //	trace
 //	debug
 //	info
@@ -100,7 +102,13 @@ func logQueryArgs(args []any) []any {
 			}
 		case string:
 			if len(v) > 64 {
-				a = fmt.Sprintf("%s (truncated %d bytes)", v[:64], len(v)-64)
+				var l int = 0
+				for w := 0; l < 64; l += w {
+					_, w = utf8.DecodeRuneInString(v[l:])
+				}
+				if len(v) > l {
+					a = fmt.Sprintf("%s (truncated %d bytes)", v[:l], len(v)-l)
+				}
 			}
 		}
 		logArgs = append(logArgs, a)
diff --git a/tracelog/tracelog_test.go b/tracelog/tracelog_test.go
index ed0f8eab..ae666066 100644
--- a/tracelog/tracelog_test.go
+++ b/tracelog/tracelog_test.go
@@ -137,6 +137,48 @@ func TestLogQuery(t *testing.T) {
 	})
 }
 
+// https://github.com/jackc/pgx/issues/1365
+func TestLogQueryArgsHandlesUTF8(t *testing.T) {
+	t.Parallel()
+
+	logger := &testLogger{}
+	tracer := &tracelog.TraceLog{
+		Logger:   logger,
+		LogLevel: tracelog.LogLevelTrace,
+	}
+
+	ctr := defaultConnTestRunner
+	ctr.CreateConfig = func(ctx context.Context, t testing.TB) *pgx.ConnConfig {
+		config := defaultConnTestRunner.CreateConfig(ctx, t)
+		config.Tracer = tracer
+		return config
+	}
+
+	pgxtest.RunWithQueryExecModes(context.Background(), t, ctr, nil, func(ctx context.Context, t testing.TB, conn *pgx.Conn) {
+		logger.logs = logger.logs[0:0] // Clear any logs written when establishing connection
+
+		var s string
+		for i := 0; i < 63; i++ {
+			s += "0"
+		}
+		s += "😊"
+
+		_, err := conn.Exec(ctx, `select $1::text`, s)
+		require.NoError(t, err)
+		require.Len(t, logger.logs, 1)
+		require.Equal(t, "Query", logger.logs[0].msg)
+		require.Equal(t, tracelog.LogLevelInfo, logger.logs[0].lvl)
+		require.Equal(t, s, logger.logs[0].data["args"].([]any)[0])
+
+		_, err = conn.Exec(ctx, `select $1::text`, s+"000")
+		require.NoError(t, err)
+		require.Len(t, logger.logs, 2)
+		require.Equal(t, "Query", logger.logs[1].msg)
+		require.Equal(t, tracelog.LogLevelInfo, logger.logs[1].lvl)
+		require.Equal(t, s+" (truncated 3 bytes)", logger.logs[1].data["args"].([]any)[0])
+	})
+}
+
 func TestLogCopyFrom(t *testing.T) {
 	t.Parallel()