fix(config): route group avatars to avatar bucket, not group bucket

config/config.go

@@ -876,10 +876,25 @@ func (c *Config) GetAvatarPath(uid string) string {
 	return fmt.Sprintf("users/%s/avatar", uid)
 }
 
-// GetGroupAvatarFilePath 获取群头像上传路径
+// GetGroupAvatarFilePath returns the object path for a group's avatar image.
+//
+// The path is routed under the "avatar" bucket so it lands in the publicly
+// readable bucket used by all avatars (user, group, community). Before this
+// fix (GH#21 / octo-server#103) the path started with "group/", which
+// routed the file into the private "group" bucket (intended for group
+// exports, not publicly served images). The MinIO / OSS splitBucketAndObject
+// helper in octo-server selects the destination bucket from the first path
+// segment when it appears in the allow-list, so "avatar/..." → avatar
+// bucket (anonymous-readable) and "group/..." → group bucket (private).
+//
+// Deployments upgrading from a version that stored group avatars under the
+// old "group/" path should either:
+//   - re-generate group avatars (trigger a group-member change), or
+//   - copy the existing objects from the "group" bucket to "avatar" bucket
+//     under the new key layout.
 func (c *Config) GetGroupAvatarFilePath(groupNo string) string {
 	avatarID := crc32.ChecksumIEEE([]byte(groupNo)) % uint32(c.Avatar.Partition)
-	return fmt.Sprintf("group/%d/%s.png", avatarID, groupNo)
+	return fmt.Sprintf("avatar/group/%d/%s.png", avatarID, groupNo)
 }
 
 // GetCommunityAvatarFilePath 获取社区头像上传路径

config/config_avatar_path_test.go

@@ -0,0 +1,70 @@
+package config
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/spf13/viper"
+)
+
+// TestGetGroupAvatarFilePath_BucketPrefix verifies that the group avatar path
+// lands in the "avatar" bucket (publicly readable), not the "group" bucket
+// (private). This is the regression guard for GH#21 / octo-server#103.
+func TestGetGroupAvatarFilePath_BucketPrefix(t *testing.T) {
+	cfg := New()
+	vp := viper.New()
+	cfg.ConfigureWithViper(vp)
+
+	path := cfg.GetGroupAvatarFilePath("g_test_12345")
+
+	// Must start with "avatar/" so splitBucketAndObject routes to the avatar bucket.
+	if !strings.HasPrefix(path, "avatar/") {
+		t.Errorf("GetGroupAvatarFilePath should start with 'avatar/' to route to the public avatar bucket, got %q", path)
+	}
+
+	// Must NOT start with "group/" — that routes to the private group bucket.
+	if strings.HasPrefix(path, "group/") {
+		t.Errorf("GetGroupAvatarFilePath must not start with 'group/' (private bucket), got %q", path)
+	}
+
+	// Must end with ".png" and contain the group number.
+	if !strings.HasSuffix(path, ".png") {
+		t.Errorf("GetGroupAvatarFilePath should end with '.png', got %q", path)
+	}
+	if !strings.Contains(path, "g_test_12345") {
+		t.Errorf("GetGroupAvatarFilePath should contain the group number, got %q", path)
+	}
+
+	// Must contain a "group/" sub-path to namespace group avatars within the avatar bucket.
+	if !strings.Contains(path, "/group/") {
+		t.Errorf("GetGroupAvatarFilePath should contain '/group/' namespace, got %q", path)
+	}
+}
+
+// TestGetGroupAvatarFilePath_Deterministic verifies the same groupNo always
+// produces the same path (partition is deterministic via CRC32).
+func TestGetGroupAvatarFilePath_Deterministic(t *testing.T) {
+	cfg := New()
+	vp := viper.New()
+	cfg.ConfigureWithViper(vp)
+
+	p1 := cfg.GetGroupAvatarFilePath("g_abc")
+	p2 := cfg.GetGroupAvatarFilePath("g_abc")
+	if p1 != p2 {
+		t.Errorf("GetGroupAvatarFilePath should be deterministic: %q != %q", p1, p2)
+	}
+}
+
+// TestGetGroupAvatarFilePath_DifferentGroups verifies distinct groups get
+// distinct paths (collision-free at the groupNo level).
+func TestGetGroupAvatarFilePath_DifferentGroups(t *testing.T) {
+	cfg := New()
+	vp := viper.New()
+	cfg.ConfigureWithViper(vp)
+
+	p1 := cfg.GetGroupAvatarFilePath("g_alice_group")
+	p2 := cfg.GetGroupAvatarFilePath("g_bob_group")
+	if p1 == p2 {
+		t.Errorf("different groups should produce different paths: both %q", p1)
+	}
+}