fix: align group private chat permission semantics

server/db/adapter.go

@@ -406,6 +406,7 @@ type TenantBusinessAdapter interface {
 	TenantGroupMemberGet(t.TenantID, string, t.Uid) (*t.GroupMember, error)
 	TenantGroupMemberList(t.TenantID, string, t.GroupMemberListOptions) ([]t.GroupMember, string, error)
 	TenantGroupMemberUpdate(t.TenantID, string, t.Uid, t.GroupMemberPatch) (*t.GroupMember, error)
+	TenantUsersShareOpenPrivateGroup(t.TenantID, t.Uid, t.Uid) (bool, error)
 	TenantGroupInvitationCreate(t.TenantID, *t.GroupInvitation) (*t.GroupInvitation, error)
 	TenantGroupInvitationAccept(t.TenantID, string, t.Uid, any, time.Time) (*t.GroupInvitation, error)
 	TenantGroupJoinRequestCreate(t.TenantID, *t.GroupJoinRequest) (*t.GroupJoinRequest, error)

server/db/mysql/group_schema_test.go

@@ -171,3 +171,24 @@ func TestSharedDBGroupFileLinkIncludesTenantID(t *testing.T) {
 		t.Fatal("TenantGroupFileCreate must not rely on im_filemsglinks.tenant_id default")
 	}
 }
+
+func TestTenantUsersShareOpenPrivateGroupChecksBothMembersAndSetting(t *testing.T) {
+	source, err := os.ReadFile("tenant_groups.go")
+	if err != nil {
+		t.Fatal(err)
+	}
+	body := sourceBetween(t, string(source), "func (a *adapter) TenantUsersShareOpenPrivateGroup", "\nfunc (a *adapter) TenantGroupMemberUpdate")
+	for _, required := range []string{
+		"INNER JOIN im_group_members AS gm2",
+		"gm2.topic=gm1.topic",
+		"INNER JOIN im_group_settings AS gs",
+		"gs.member_private_chat=1",
+		"gm1.member_status=?",
+		"gm2.member_status=?",
+		"gs.group_status=?",
+	} {
+		if !strings.Contains(body, required) {
+			t.Fatalf("TenantUsersShareOpenPrivateGroup must check active shared group and setting; missing %q", required)
+		}
+	}
+}

server/db/mysql/tenant_groups.go

@@ -394,6 +394,39 @@ func (a *adapter) TenantGroupMemberList(id t.TenantID, topic string, opts t.Grou
 	return items, next, rows.Err()
 }
 
+func (a *adapter) TenantUsersShareOpenPrivateGroup(id t.TenantID, userID, peerID t.Uid) (bool, error) {
+	if tenantAdp, err := a.routeGroupTenant(id); err != nil {
+		return false, err
+	} else if tenantAdp != a {
+		return tenantAdp.TenantUsersShareOpenPrivateGroup(id, userID, peerID)
+	}
+	if userID.IsZero() || peerID.IsZero() || userID == peerID {
+		return false, t.ErrMalformed
+	}
+	ctx, cancel := a.getContext()
+	if cancel != nil {
+		defer cancel()
+	}
+	var exists int
+	err := a.db.GetContext(ctx, &exists, tenantShardSQL(id, `
+		SELECT 1
+		FROM im_group_members AS gm1
+		INNER JOIN im_group_members AS gm2
+			ON gm2.tenant_id=gm1.tenant_id AND gm2.topic=gm1.topic
+		INNER JOIN im_group_settings AS gs
+			ON gs.tenant_id=gm1.tenant_id AND gs.topic=gm1.topic
+		WHERE gm1.tenant_id=? AND gm1.user_id=? AND gm1.member_status=?
+			AND gm2.user_id=? AND gm2.member_status=?
+			AND gs.group_status=? AND gs.member_private_chat=1
+		LIMIT 1`),
+		id, decodeUID(userID), t.GroupMemberStatusActive,
+		decodeUID(peerID), t.GroupMemberStatusActive, t.GroupStatusActive)
+	if err == sql.ErrNoRows {
+		return false, nil
+	}
+	return exists == 1, err
+}
+
 func (a *adapter) TenantGroupMemberUpdate(id t.TenantID, topic string, uid t.Uid, patch t.GroupMemberPatch) (*t.GroupMember, error) {
 	if tenantAdp, err := a.routeGroupTenant(id); err != nil {
 		return nil, err