Improve error message on invalid headers

lib/hpax.ex

@@ -298,7 +298,8 @@ defmodule HPAX do
   end
 
   defp encode_headers([{action, name, value} | rest], table, acc)
-       when action in @valid_header_actions and is_binary(name) and is_binary(value) do
+       when action in @valid_header_actions do
+    validate_header(name, value)
     huffman? = table.huffman_encoding == :always
 
     {encoded, table} =
@@ -330,6 +331,15 @@ defmodule HPAX do
     encode_headers(rest, table, [acc, encoded])
   end
 
+  defp validate_header(name, value) when is_binary(name) and is_binary(value) do
+    :ok
+  end
+
+  defp validate_header(name, value) do
+    raise ArgumentError,
+          "expected header name/value to be strings, got: #{inspect(name)}/#{inspect(value)}"
+  end
+
   defp encode_indexed_header(index) do
     <<1::1, Types.encode_integer(index, 7)::bitstring>>
   end

test/hpax_test.exs

@@ -95,6 +95,22 @@ defmodule HPAXTest do
     assert dec_table.entries == [{"b", "B"}, {"a", "A"}]
   end
 
+  test "encode/3 with invalid headers" do
+    table = HPAX.new(1000)
+
+    assert_raise ArgumentError,
+                 ~s(expected header name/value to be strings, got: :foo/"bar"),
+                 fn ->
+                   HPAX.encode([{:store, :foo, "bar"}], table)
+                 end
+
+    assert_raise ArgumentError,
+                 ~s(expected header name/value to be strings, got: "foo"/:bar),
+                 fn ->
+                   HPAX.encode([{:store, "foo", :bar}], table)
+                 end
+  end
+
   property "encode/3 with a single action" do
     table = HPAX.new(500)