Format inserted/deleted maps in list assertions

lib/ex_unit/lib/ex_unit/diff.ex

@@ -558,15 +558,15 @@ defmodule ExUnit.Diff do
   end
 
   defp move_right({y, list1, [elem2 | rest2], {edit1, edit2, env}}) do
-    {y, list1, rest2, {edit1, [{:ins, elem2} | edit2], env}}
+    {y, list1, rest2, {edit1, [{:ins, build_elem(elem2)} | edit2], env}}
   end
 
   defp move_right({y, list1, [], edits}) do
     {y, list1, [], edits}
   end
 
   defp move_down({y, [elem1 | rest1], list2, {edit1, edit2, env}}) do
-    {y + 1, rest1, list2, {[{:del, elem1} | edit1], edit2, env}}
+    {y + 1, rest1, list2, {[{:del, build_elem(elem1)} | edit1], edit2, env}}
   end
 
   defp move_down({y, [], list2, edits}) do
@@ -763,6 +763,10 @@ defmodule ExUnit.Diff do
     _ -> :error
   end
 
+  def build_elem(elem) when is_struct(elem), do: elem
+  def build_elem(elem) when is_map(elem), do: {:%{}, [], Map.to_list(elem)}
+  def build_elem(elem), do: elem
+
   defp maybe_struct(%name{}), do: name
   defp maybe_struct(_), do: nil
 
@@ -1145,6 +1149,9 @@ defmodule ExUnit.Diff do
   # We escape container types to make a distinction between AST
   # and values that should be inspected. All other values have no
   # special AST representation, so we can keep them as is.
+  # Maps should be formatted not inspected.
+  defp escape(other) when is_struct(other), do: {other}
+  defp escape({:%{}, _, _} = other), do: other
   defp escape(other) when is_list(other) or is_tuple(other), do: {other}
   defp escape(other), do: other
 

lib/ex_unit/test/ex_unit/formatter_test.exs

@@ -469,6 +469,58 @@ defmodule ExUnit.FormatterTest do
            """
   end
 
+  test "formats nested maps with column limit" do
+    map =
+      %{
+        microsecond: {1, 2},
+        second: 3,
+        month: 4,
+        day: 5,
+        year: 2024,
+        minute: 6,
+        hour: 7
+      }
+
+    failure = [{:error, catch_assertion(assert [map, %{map | hour: 8}] == [map]), []}]
+
+    assert format_test_all_failure(test_module(), failure, 1, 80, &formatter/2) == """
+             1) Hello: failure on setup_all callback, all tests have been invalidated
+                Assertion with == failed
+                code:  assert [map, %{map | hour: 8}] == [map]
+                left:  [
+                         %{
+                           microsecond: {1, 2},
+                           second: 3,
+                           month: 4,
+                           day: 5,
+                           year: 2024,
+                           minute: 6,
+                           hour: 7
+                         },
+                         %{
+                           microsecond: {1, 2},
+                           second: 3,
+                           month: 4,
+                           day: 5,
+                           year: 2024,
+                           minute: 6,
+                           hour: 8
+                         }
+                       ]
+                right: [
+                         %{
+                           microsecond: {1, 2},
+                           second: 3,
+                           month: 4,
+                           day: 5,
+                           year: 2024,
+                           minute: 6,
+                           hour: 7
+                         }
+                       ]
+           """
+  end
+
   test "formats assertions with complex function call arguments" do
     failure = [{:error, catch_assertion(assert is_list(List.to_tuple([1, 2, 3]))), []}]