More verbose reporting

eventauth.go

@@ -1019,7 +1019,7 @@ func (m *membershipAllower) membershipAllowedSelf() error { // nolint: gocyclo
 	}
 	if m.newMember.Membership == Knock {
 		if m.joinRule.JoinRule != Knock {
-			return m.membershipFailed()
+			return errorf("the join rule %q does not allow knocking", m.joinRule.JoinRule)
 		}
 		// A user that is not in the room is allowed to knock if the join
 		// rules are "knock" and they are not already joined to, invited to
@@ -1028,13 +1028,13 @@ func (m *membershipAllower) membershipAllowedSelf() error { // nolint: gocyclo
 		if supported, err := m.roomVersion.AllowKnockingInEventAuth(); err != nil {
 			return fmt.Errorf("m.roomVersion.AllowKnockingInEventAuth: %w", err)
 		} else if !supported {
-			return m.membershipFailed()
+			return errorf("knocking is not supported in room version %q", m.roomVersion)
 		}
 		switch m.oldMember.Membership {
 		case Join, Invite, Ban:
 			// The user is already joined, invited or banned, therefore they
 			// can't knock.
-			return m.membershipFailed()
+			return errorf("the knocking user is already joined/invited/banned")
 		default:
 			// A non-joined, non-invited, non-banned user is allowed to knock.
 			return nil
@@ -1122,11 +1122,14 @@ func (m *membershipAllower) membershipAllowedOther() error { // nolint: gocyclo
 			return nil
 		}
 		// A user can invite in response to a knock.
-		if m.joinRule.JoinRule == Knock && m.oldMember.Membership == Knock && senderLevel >= m.powerLevels.Invite {
+		if m.oldMember.Membership == Knock && senderLevel >= m.powerLevels.Invite {
+			if m.joinRule.JoinRule != Knock {
+				return errorf("the join rule %q does not allow knocking", m.joinRule.JoinRule)
+			}
 			if supported, err := m.roomVersion.AllowKnockingInEventAuth(); err != nil {
 				return fmt.Errorf("m.roomVersion.AllowKnockingInEventAuth: %w", err)
 			} else if !supported {
-				return m.membershipFailed()
+				return errorf("knocking is not supported in room version %q", m.roomVersion)
 			}
 			return nil
 		}