fix(membership-fees): show error for unparseable cycle date instead of crashing

Date.from_iso8601/1 returns {:error, reason}, so the with else clause matching a bare :error never fired and an invalid date raised a WithClauseError. Match the real date/calendar error reasons so the user sees the validation message.

lib/mv_web/live/member_live/show/membership_fees_component.ex

@@ -1027,7 +1027,7 @@ defmodule MvWeb.MemberLive.Show.MembershipFeesComponent do
            |> assign(:create_cycle_error, format_error(error))}
       end
     else
-      :error ->
+      {:error, reason} when reason in [:invalid_format, :invalid_date, :incompatible_calendars] ->
         {:noreply,
          socket
          |> assign(:create_cycle_error, gettext("Invalid date format"))}

test/mv_web/member_live/show_membership_fees_test.exs

@@ -268,6 +268,28 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
       # Should not crash
       assert html =~ member.first_name
     end
+
+    test "create_cycle with an unparseable date shows an error instead of crashing", %{conn: conn} do
+      fee_type = create_fee_type(%{interval: :yearly})
+      member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
+
+      {:ok, view, _html} = live(conn, "/members/#{member.id}")
+
+      view
+      |> element("button[phx-click='switch_tab'][phx-value-tab='membership_fees']")
+      |> render_click()
+
+      view
+      |> element("button[phx-click='open_create_cycle_modal']")
+      |> render_click()
+
+      html =
+        view
+        |> element("form[phx-submit='create_cycle']")
+        |> render_submit(%{"date" => "not-a-date", "amount" => "10"})
+
+      assert html =~ "Invalid date format"
+    end
   end
 
   describe "read_only user (Vorstand/Buchhaltung) - no cycle action buttons" do