markdown: conditionally copy assets to target dir

lib/ex_doc/formatter/markdown.ex

@@ -6,6 +6,15 @@ defmodule ExDoc.Formatter.MARKDOWN do
   def run(config, project_nodes, extras) when is_map(config) do
     File.mkdir_p!(config.output)
 
+    static_files =
+      if Enum.all?(config.assets, fn {_k, target_dir} ->
+           config.output |> Path.join(target_dir) |> File.exists?()
+         end) do
+        []
+      else
+        ExDoc.Formatter.copy_assets(config.assets, config.output)
+      end
+
     {modules, tasks} =
       project_nodes
       |> Enum.filter(&(&1.source_format == "text/markdown"))
@@ -16,7 +25,8 @@ defmodule ExDoc.Formatter.MARKDOWN do
         generate_api_reference(config, modules, tasks) ++
         generate_extras(config, extras) ++
         generate_list(config, modules) ++
-        generate_list(config, tasks)
+        generate_list(config, tasks) ++
+        static_files
 
     entrypoint = config.output |> Path.join("llms.txt") |> Path.relative_to_cwd()
     %{entrypoint: entrypoint, build: List.flatten(all_files)}

test/ex_doc/formatter/markdown_test.exs

@@ -288,4 +288,28 @@ defmodule ExDoc.Formatter.MarkdownTest do
                "*Consult [api-reference.md](api-reference.md) for complete listing*"
     end
   end
+
+  describe "assets" do
+    test "copies assets from source", %{tmp_dir: tmp_dir} = context do
+      dir_name = Path.join(tmp_dir, "hello")
+      File.mkdir!(dir_name)
+      dir_name |> Path.join("world") |> File.touch!()
+
+      config = config(context, assets: %{dir_name => "assets"})
+
+      generate(config)
+
+      assert File.regular?(tmp_dir <> "/assets/world")
+    end
+
+    test "does not override previous work from other formatters", %{tmp_dir: tmp_dir} = context do
+      dir_name = Path.join(tmp_dir, "assets")
+      File.mkdir!(dir_name)
+      info = File.stat!(dir_name)
+      config = config(context, assets: %{"test/tmp/markdown_assets/hello" => "assets"})
+      generate(config)
+
+      assert File.stat!(dir_name) == info
+    end
+  end
 end