Bug: unbalanced <li> tag emitted in synopsis

[adamwight]

While consuming ex_doc epub output and running through a strict linter, I discovered that ex_doc is emitting some bad HTML. This task concerns the broken tags produced by the ExDoc.Formatter.HTML.Templates.synopsis/1 function.

Given minimal .ex input as follows,

defmodule ImbalanceTest do
  @doc """
  ## Options

  - one

  - two
  """
  def nonsense do
  end
end

The low-level method gets called like this,

iex> ExDoc.Formatter.HTML.Templates.synopsis("<h2>Options</h2><ul><li><p>one</p></li><li><p>two</p></li></ul>")
"<h2>Options</h2><ul><li><p>one</p>"

The <p> between list items seems to be key to triggering this bug.

[adamwight]

Here's a shorter, direct invocation which can be turned into a unit test:

iex> ExDoc.Formatter.HTML.Templates.synopsis("<li><p>one</p></li>")
"<li><p>one</p>"

[adamwight]

I've submitted a small patch, but in the long term it seems better to go more in the direction of structured HTML manipulation, eg.

doc
|> Floki.parse_fragment!()
|> Floki.find("p:first-of-type")
|> Floki.raw_html()