Reduce limit as we traverse collections on inspect

Author: José Valim

lib/elixir/lib/inspect/algebra.ex

@@ -453,21 +453,23 @@ defmodule Inspect.Algebra do
     "..."
   end
 
-  defp do_surround_many([h], _limit, opts, fun, _sep) do
-    fun.(h, opts)
+  defp do_surround_many([h], limit, opts, fun, _sep) do
+    fun.(h, %{opts | limit: limit})
   end
 
   defp do_surround_many([h|t], limit, opts, fun, sep) when is_list(t) do
+    limit = decrement(limit)
     glue(
-      concat(fun.(h, opts), sep),
-      do_surround_many(t, decrement(limit), opts, fun, sep)
+      concat(fun.(h, %{opts | limit: limit}), sep),
+      do_surround_many(t, limit, opts, fun, sep)
     )
   end
 
-  defp do_surround_many([h|t], _limit, opts, fun, _sep) do
+  defp do_surround_many([h|t], limit, opts, fun, _sep) do
+    limit = decrement(limit)
     glue(
-      concat(fun.(h, opts), @tail_separator),
-      fun.(t, opts)
+      concat(fun.(h, %{opts | limit: limit}), @tail_separator),
+      fun.(t, %{opts | limit: limit})
     )
   end
 

lib/elixir/test/elixir/inspect_test.exs

@@ -190,12 +190,19 @@ defmodule Inspect.ListTest do
     assert inspect([{:b, 1}, {:a, 1}]) == "[b: 1, a: 1]"
   end
 
-  test :unproper do
+  test :improper do
     assert inspect([:foo | :bar]) == "[:foo | :bar]"
 
     assert inspect([1,2,3,4,5|42], [pretty: true, width: 1]) == "[1,\n 2,\n 3,\n 4,\n 5 |\n 42]"
   end
 
+  test :nested do
+    assert inspect(Enum.reduce(1..100, [0], &[&2 , Integer.to_string(&1)]), [limit: 5]) ==
+           "[[[[[[...], ...], \"97\"], \"98\"], \"99\"], \"100\"]"
+    assert inspect(Enum.reduce(1..100, [0], &[&2 | Integer.to_string(&1)]), [limit: 5]) ==
+           "[[[[[[...] | \"96\"] | \"97\"] | \"98\"] | \"99\"] | \"100\"]"
+  end
+
   test :codepoints do
     assert inspect('é') == "[233]"
   end