From 068ba02412ae1bbdf14bd1042b853290b3cda410 Mon Sep 17 00:00:00 2001
From: Matt Enlow <matt@novaugust.net>
Date: Fri, 21 Jun 2024 02:03:24 -0600
Subject: [PATCH] Allow anchors on function and callback autolinks (#1921)

---
 lib/ex_doc/autolink.ex               | 10 ++++++++--
 test/ex_doc/language/elixir_test.exs |  5 +++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/ex_doc/autolink.ex b/lib/ex_doc/autolink.ex
index b26d55df5..f7beb46fe 100644
--- a/lib/ex_doc/autolink.ex
+++ b/lib/ex_doc/autolink.ex
@@ -335,8 +335,8 @@ defmodule ExDoc.Autolink do
   end
 
   defp parse_url(string, mode, config) do
-    case Regex.run(~r{^(.+)/(\d+)$}, string) do
-      [_, left, right] ->
+    case Regex.run(~r{^(.+)/(\d+)(#.*)?$}, string) do
+      [_, left, right | maybe_fragment] ->
         with {:ok, arity} <- parse_arity(right) do
           {kind, rest} = kind(left)
 
@@ -344,11 +344,13 @@ defmodule ExDoc.Autolink do
             {:local, function} ->
               kind
               |> local_url(function, arity, config, string, mode: mode)
+              |> maybe_append_nested_fragment(maybe_fragment)
               |> maybe_remove_link(mode)
 
             {:remote, module, function} ->
               {kind, module, function, arity}
               |> remote_url(config, string, mode: mode)
+              |> maybe_append_nested_fragment(maybe_fragment)
               |> maybe_remove_link(mode)
 
             :error ->
@@ -611,6 +613,10 @@ defmodule ExDoc.Autolink do
   def format_visibility(:undefined, _kind), do: "undefined or private"
   def format_visibility(visibility, _kind), do: "#{visibility}"
 
+  defp maybe_append_nested_fragment(nil, _), do: nil
+  defp maybe_append_nested_fragment(url, []), do: url
+  defp maybe_append_nested_fragment(url, ["#" <> fragment]), do: url <> "-" <> fragment
+
   defp append_fragment(url, nil), do: url
   defp append_fragment(url, fragment), do: url <> "#" <> fragment
 end
diff --git a/test/ex_doc/language/elixir_test.exs b/test/ex_doc/language/elixir_test.exs
index 69b4b8eb4..8af557826 100644
--- a/test/ex_doc/language/elixir_test.exs
+++ b/test/ex_doc/language/elixir_test.exs
@@ -148,6 +148,11 @@ defmodule ExDoc.Language.ElixirTest do
                ~s|<a href="https://hexdocs.pm/elixir/GenServer.html#c:handle_call/3"><code class="inline">GenServer.handle_call/3</code></a>|
     end
 
+    test "elixir callback fragment" do
+      assert autolink_doc("`c:GenServer.handle_call/3#fragment`") ==
+               ~s|<a href="https://hexdocs.pm/elixir/GenServer.html#c:handle_call/3-fragment"><code class="inline">GenServer.handle_call/3</code></a>|
+    end
+
     test "erlang callback" do
       assert autolink_doc("`c::gen_server.handle_call/3`") ==
                ~s|<a href="https://www.erlang.org/doc/apps/stdlib/gen_server.html#c:handle_call/3"><code class="inline">:gen_server.handle_call/3</code></a>|