Set column width from the first row when headers are not given

lib/exceed/worksheet.ex

@@ -63,7 +63,7 @@ defmodule Exceed.Worksheet do
             })
           ]),
           Xs.empty_element("sheetFormatPr", %{"baseColWidth" => "8", "defaultRowHeight" => "18"}),
-          cols(headers, opts),
+          cols(headers, content, opts),
           Xs.element("sheetData", sheet_data(content, headers)),
           Xs.empty_element("sheetCalcPr", %{"fullCalcOnLoad" => "1"}),
           Xs.empty_element("printOptions", %{
@@ -89,15 +89,19 @@ defmodule Exceed.Worksheet do
 
   # # #
 
-  defp cols(nil, _), do: []
+  defp cols(nil, content, opts) do
+    case content |> Stream.take(1) |> Enum.to_list() do
+      [headers] -> cols(headers, content, opts)
+    end
+  end
 
-  defp cols(headers, opts) do
+  defp cols(headers, _content, opts) do
     padding = Keyword.get(opts, :col_padding, 4.25)
 
     Xs.element(
       "cols",
       for {header, i} <- Enum.with_index(headers, 1) do
-        width = String.length(header) + padding
+        width = String.length(to_string(header)) + padding
         Xs.empty_element("col", %{"min" => i, "max" => i, "width" => width})
       end
     )

test/exceed/worksheet_test.exs

@@ -126,6 +126,16 @@ defmodule Exceed.WorksheetTest do
       assert String.length(header3) == 6
       assert Xq.attr(col3, "width") == "8.34"
     end
+
+    test "uses the first row of the stream to set column width when headers are not given", %{stream: stream} do
+      ws = Worksheet.new("sheet", nil, Enum.take(stream, 2))
+      xml = Worksheet.to_xml(ws) |> stream_to_xml()
+
+      assert [col1, col2, col3] = Xq.all(xml, "/worksheet/cols/col")
+      assert Xq.attr(col1, "width") == "16.25"
+      assert Xq.attr(col2, "width") == "5.25"
+      assert Xq.attr(col3, "width") == "7.25"
+    end
   end
 
   # # #