Fix crash on HTML comments in incoming messages

Author: progval

lib/format/matrix2irc.ex

@@ -33,6 +33,10 @@ defmodule M51.Format.Matrix2Irc do
     end
   end
 
+  def transform({:comment, _comment}, _state) do
+    ""
+  end
+
   def transform({"a", attributes, children}, state) do
     case attributes |> Map.new() |> Map.get("href") do
       nil ->

test/format/common_test.exs

@@ -335,4 +335,8 @@ defmodule M51.FormatTest do
     assert M51.Format.matrix2irc("join <a href=\"https://matrix.to/#/%23\">oh no</a>") ==
              "join oh no <https://matrix.to/#/%23\>"
   end
+
+  test "HTML comment" do
+    assert M51.Format.matrix2irc("foo <!-- bar --> baz") == "foo  baz"
+  end
 end