Compile attrs at runtime to enable interpolation

lib/dsl/html.ex

@@ -56,7 +56,8 @@ defmodule Dsl.Html do
       el = unquote(el)
 
       quote do
-        put_buffer(var!(buff, Dsl.Html), "<#{unquote(el)}#{unquote(compile_attrs(attrs))}>")
+        attrs = unquote(attrs)
+        put_buffer(var!(buff, Dsl.Html), "<#{unquote(el)}#{compile_attrs(attrs)}>")
         unquote(inner)
         put_buffer(var!(buff, Dsl.Html), "</#{unquote(el)}>")
       end
@@ -123,9 +124,9 @@ defmodule Dsl.Html do
 
   def insert_props(ast, _inner), do: ast
 
-  defp compile_attrs([]), do: ""
+  def compile_attrs([]), do: ""
 
-  defp compile_attrs(attrs) do
+  def compile_attrs(attrs) do
     for {name, value} <- attrs, into: "" do
       name = name |> Atom.to_string() |> String.replace("_", "-")
 

test/dsl/html_test.exs

@@ -275,5 +275,16 @@ defmodule Dsl.HtmlTest do
       assert result ==
                ~s|<div>:atom</div><div>%{key: &quot;value&quot;}</div><div>{:status, :tuple}</div><div>&quot;string&quot;</div><div>1</div><div>[1, 2, 3]</div>|
     end
+
+    test "can use string interpolation in props" do
+      interop = "hi"
+
+      {:safe, result} =
+        htm do
+          div(class: "#{interop} world")
+        end
+
+      assert result == ~s{<div class="hi world"></div>}
+    end
   end
 end