Improved processing of attachments (#35854) (#36103)

# Conflicts:
#	server/channels/app/slack.go

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/slack.go

@@ -91,7 +91,7 @@ func (a *App) ProcessSlackText(text string) string {
 // documented here: https://api.slack.com/docs/attachments
 func (a *App) ProcessSlackAttachments(attachments []*model.SlackAttachment) []*model.SlackAttachment {
 	var nonNilAttachments = model.StringifySlackFieldValue(attachments)
-	for _, attachment := range attachments {
+	for _, attachment := range nonNilAttachments {
 		attachment.Pretext = a.ProcessSlackText(attachment.Pretext)
 		attachment.Text = a.ProcessSlackText(attachment.Text)
 		attachment.Title = a.ProcessSlackText(attachment.Title)

server/channels/app/slack_test.go

@@ -6,6 +6,8 @@ package app
 import (
 	"testing"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/mattermost/mattermost/server/public/model"
 )
 
@@ -33,6 +35,31 @@ func TestProcessSlackText(t *testing.T) {
 	}
 }
 
+func TestProcessMessageAttachmentsWithNilEntries(t *testing.T) {
+	mainHelper.Parallel(t)
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	attachments := []*model.SlackAttachment{
+		nil,
+		{
+			Pretext: "pretext",
+			Text:    "text",
+			Title:   "title",
+		},
+		nil,
+		{
+			Pretext: "pretext2",
+			Text:    "text2",
+		},
+	}
+
+	result := th.App.ProcessSlackAttachments(attachments)
+	require.Len(t, result, 2)
+	require.Equal(t, "pretext", result[0].Pretext)
+	require.Equal(t, "pretext2", result[1].Pretext)
+}
+
 func TestProcessSlackAnnouncement(t *testing.T) {
 	mainHelper.Parallel(t)
 	th := Setup(t).InitBasic()

server/channels/app/webhook.go

@@ -125,6 +125,14 @@ func (a *App) TriggerWebhook(c request.CTX, payload *model.OutgoingWebhookPayloa
 
 		go func() {
 			defer wg.Done()
+			defer func() {
+				if r := recover(); r != nil {
+					logger.Error("Recovered from panic in outgoing webhook goroutine",
+						mlog.String("url", url),
+						mlog.Any("panic", r),
+					)
+				}
+			}()
 
 			var accessToken *model.OutgoingOAuthConnectionToken