Warn when trying to reference types in hidden modules (#1940)

Author: voughtdq

lib/ex_doc/autolink.ex

@@ -511,6 +511,18 @@ defmodule ExDoc.Autolink do
              (config.language != ExDoc.Language.Erlang or kind == :function) ->
         nil
 
+      {:regular_link, :hidden, :hidden}
+      when not same_module? ->
+        if warn? do
+          maybe_warn(config, ref, :hidden, %{
+            original_text: original_text,
+            module_visibility: :hidden,
+            same_module?: false
+          })
+        end
+
+        nil
+
       {_mode, _module_visibility, visibility} ->
         if warn? do
           maybe_warn(config, ref, visibility, %{original_text: original_text})
@@ -585,6 +597,19 @@ defmodule ExDoc.Autolink do
     warn(config, message)
   end
 
+  defp warn(
+         config,
+         {:type, module, _name, _arity},
+         :hidden,
+         %{original_text: original_text, module_visibility: :hidden, same_module?: false}
+       ) do
+    message =
+      "documentation references type \"#{original_text}\" but the module " <>
+        "#{inspect(module)} is #{format_visibility(:hidden, :module)}"
+
+    warn(config, message)
+  end
+
   defp warn(
          config,
          {kind, _module, _name, _arity},

test/ex_doc/language/elixir_test.exs

@@ -500,7 +500,9 @@ defmodule ExDoc.Language.ElixirTest do
     ExDoc.Refs.insert([
       {{:module, AutolinkTest.Foo}, :public},
       {{:function, AutolinkTest.Foo, :bar, 1}, :hidden},
-      {{:type, AutolinkTest.Foo, :bad, 0}, :hidden}
+      {{:type, AutolinkTest.Foo, :bad, 0}, :hidden},
+      {{:module, AutoLinkTest.Hidden}, :hidden},
+      {{:type, AutoLinkTest.Hidden, :my_type, 0}, :hidden}
     ])
 
     opts = [
@@ -519,6 +521,12 @@ defmodule ExDoc.Language.ElixirTest do
     assert message =~ ~s|references function "AutolinkTest.Foo.bar/1" but it is hidden|
     assert metadata == [file: "foo.ex", line: 2]
 
+    assert warn(fn ->
+             assert autolink_doc("`t:AutoLinkTest.Hidden.my_type/0`", opts) ==
+                      ~s|<code class="inline">t:AutoLinkTest.Hidden.my_type/0</code>|
+           end) =~
+             ~s|documentation references type "t:AutoLinkTest.Hidden.my_type/0" but the module AutoLinkTest.Hidden is hidden|
+
     assert warn(fn ->
              assert autolink_doc("`t:AutolinkTest.Foo.bad/0`", opts) ==
                       ~s|<code class="inline">t:AutolinkTest.Foo.bad/0</code>|