From 41b41cc599757b2334b27479e78d149c435a1d8d Mon Sep 17 00:00:00 2001
From: Raphael Fakhri <153192858+RaphaelFakhri@users.noreply.github.com>
Date: Tue, 29 Sep 2026 10:40:47 +0000
Subject: [PATCH] ably: fix broken log format when presence history data fails
 to decode

RESTPresence history logged the decode failure with %w, which the logger's
Printf-style formatting renders as %!w(...). Use %v, as the message
decoders in rest_channel.go do.
---
 ably/rest_presence.go      |  2 +-
 ably/rest_presence_test.go | 78 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+), 1 deletion(-)
 create mode 100644 ably/rest_presence_test.go

diff --git a/ably/rest_presence.go b/ably/rest_presence.go
index 9fb4728d..de9604d0 100644
--- a/ably/rest_presence.go
+++ b/ably/rest_presence.go
@@ -248,7 +248,7 @@ func (t *fullPresenceDecoder) decodeMessagesData() {
 		m.Message, err = m.Message.withDecodedData(cipher)
 		if err != nil {
 			// RSL6b
-			t.c.log().Errorf("Couldn't fully decode presence message data from channel %q: %w", t.c.Name, err)
+			t.c.log().Errorf("Couldn't fully decode presence message data from channel %q: %v", t.c.Name, err)
 		}
 	}
 }
diff --git a/ably/rest_presence_test.go b/ably/rest_presence_test.go
new file mode 100644
index 00000000..d3a3fc30
--- /dev/null
+++ b/ably/rest_presence_test.go
@@ -0,0 +1,78 @@
+//go:build !integration
+// +build !integration
+
+package ably_test
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+
+	"github.com/ably/ably-go/ably"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type recordingLogger struct {
+	mtx  sync.Mutex
+	logs []string
+}
+
+func (l *recordingLogger) Printf(level ably.LogLevel, format string, v ...interface{}) {
+	l.mtx.Lock()
+	defer l.mtx.Unlock()
+	l.logs = append(l.logs, fmt.Sprintf(format, v...))
+}
+
+func (l *recordingLogger) lines() []string {
+	l.mtx.Lock()
+	defer l.mtx.Unlock()
+	return append([]string(nil), l.logs...)
+}
+
+func TestRESTPresence_HistoryLogsDecodeFailure(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		rw.Header().Set("Content-Type", "application/json")
+		rw.Write([]byte(`[{"action":2,"clientId":"a","data":"x","encoding":"nonsense"}]`))
+	}))
+	defer server.Close()
+
+	serverURL, err := url.Parse(server.URL)
+	assert.NoError(t, err)
+	port, err := strconv.Atoi(serverURL.Port())
+	assert.NoError(t, err)
+
+	logger := &recordingLogger{}
+	client, err := ably.NewREST(
+		ably.WithTLS(false),
+		ably.WithToken("token"),
+		ably.WithUseBinaryProtocol(false),
+		ably.WithEndpoint(serverURL.Hostname()),
+		ably.WithPort(port),
+		ably.WithLogLevel(ably.LogError),
+		ably.WithLogHandler(logger),
+	)
+	assert.NoError(t, err)
+
+	pages, err := client.Channels.Get("test").Presence.History().Pages(context.Background())
+	assert.NoError(t, err)
+	assert.True(t, pages.Next(context.Background()))
+	assert.Len(t, pages.Items(), 1)
+
+	var found string
+	for _, line := range logger.lines() {
+		if strings.Contains(line, "Couldn't fully decode presence message data") {
+			found = line
+		}
+	}
+	if assert.NotEmpty(t, found, "expected a decode failure to be logged") {
+		assert.NotContains(t, found, "%!", "log line has a formatting error: %s", found)
+		assert.Contains(t, found, "unknown encoding nonsense")
+	}
+}