backport #4145

Author: SteffenDE

lib/phoenix_live_view/tag_engine.ex

@@ -1098,7 +1098,11 @@ defmodule Phoenix.LiveView.TagEngine do
   defp handle_tag_attrs(state, meta, attrs) do
     Enum.reduce(attrs, state, fn
       {:root, {:expr, _, _} = expr, _attr_meta}, state ->
-        ast = parse_expr!(expr, state.file)
+        ast =
+          case parse_expr!(expr, state.file) do
+            {:@, _, _} = ast -> ast
+            ast -> expand_with_line(ast, meta[:line], state.caller)
+          end
 
         # If we have a map of literal keys, we unpack it as a list
         # to simplify the downstream check.

test/phoenix_live_view/html_engine_test.exs

@@ -44,6 +44,13 @@ defmodule Phoenix.LiveView.HTMLEngineTest do
     end
   end
 
+  defmacro test_attr_macro(a) do
+    case a do
+      :base -> quote do: [{"style", "display: flex;"}, {"other", "foo"}, {"another", @bar}]
+      _ -> quote do: a
+    end
+  end
+
   def assigns_component(assigns) do
     ~H"{inspect(Map.delete(assigns, :__changed__))}"
   end
@@ -216,6 +223,15 @@ defmodule Phoenix.LiveView.HTMLEngineTest do
 
     assert %Phoenix.LiveView.Rendered{static: ["<div", " d2=\"2\"", "></div>"]} =
              eval(template, assigns)
+
+    # macro is expanded
+    template = ~S|<div {test_attr_macro(:base)} />|
+
+    assert %Phoenix.LiveView.Rendered{static: ["<div style=\"", "\" other=\"foo\"", "></div>"]} =
+             eval(template, %{bar: "baz"})
+
+    assert render(template, %{bar: "baz"}) ==
+             ~S|<div style="display: flex;" other="foo" another="baz"></div>|
   end
 
   test "optimizes attributes with literal string values" do