Better ActionText plain text output for nested lists (#37976)

* Improve plaintext output for nested lists

* Update plain_text_conversion_test.rb

* Add additional test cases

* Refactor a bit

* Add changelog entry

* Rearrange methods

Co-authored-by: Matt Swanson <matt@mdswanson.com>

actiontext/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Fix an issue with how nested lists were displayed when converting to plain text
+
+    *Matt Swanson*
+
 *   Allow passing in a custom `direct_upload_url` or `blob_url_template` to `rich_text_area_tag`.
 
     *Lucas Mansur*

actiontext/lib/action_text/plain_text_conversion.rb

@@ -33,10 +33,18 @@ module ActionText
         "#{remove_trailing_newlines(plain_text_for_node_children(node))}\n\n"
       end
 
-      %i[ h1 p ul ol ].each do |element|
+      %i[ h1 p ].each do |element|
         alias_method :"plain_text_for_#{element}_node", :plain_text_for_block
       end
 
+      def plain_text_for_list(node, index)
+        "#{break_if_nested_list(node, plain_text_for_block(node))}"
+      end
+
+      %i[ ul ol ].each do |element|
+        alias_method :"plain_text_for_#{element}_node", :plain_text_for_list
+      end
+
       def plain_text_for_br_node(node, index)
         "\n"
       end
@@ -61,7 +69,9 @@ module ActionText
       def plain_text_for_li_node(node, index)
         bullet = bullet_for_li_node(node, index)
         text = remove_trailing_newlines(plain_text_for_node_children(node))
-        "#{bullet} #{text}\n"
+        indentation = indentation_for_li_node(node)
+
+        "#{indentation}#{bullet} #{text}\n"
       end
 
       def remove_trailing_newlines(text)
@@ -79,5 +89,24 @@ module ActionText
       def list_node_name_for_li_node(node)
         node.ancestors.lazy.map(&:name).grep(/^[uo]l$/).first
       end
+
+      def indentation_for_li_node(node)
+        depth = list_node_depth_for_node(node)
+        if depth > 1
+          "  " * (depth - 1)
+        end
+      end
+
+      def list_node_depth_for_node(node)
+        node.ancestors.map(&:name).grep(/^[uo]l$/).count
+      end
+
+      def break_if_nested_list(node, text)
+        if list_node_depth_for_node(node) > 0
+          "\n#{text}"
+        else
+          text
+        end
+      end
   end
 end

actiontext/test/unit/plain_text_conversion_test.rb

@@ -52,6 +52,27 @@ class ActionText::PlainTextConversionTest < ActiveSupport::TestCase
     )
   end
 
+  test "basic nested <ul> tags are indented" do
+    assert_converted_to(
+      "• Item 1\n  • Item 2",
+      "<ul><li>Item 1<ul><li>Item 2</li></ul></li></ul>"
+    )
+  end
+
+  test "basic nested <ol> tags are indented" do
+    assert_converted_to(
+      "1. Item 1\n  1. Item 2",
+      "<ol><li>Item 1<ol><li>Item 2</li></ol></li></ol>"
+    )
+  end
+
+  test "complex nested / mixed list tags are indented" do
+    assert_converted_to(
+      "• Item 0\n• Item 1\n  • Item A\n    1. Item i\n    2. Item ii\n  • Item B\n    • Item i\n• Item 2",
+      "<ul><li>Item 0</li><li>Item 1<ul><li>Item A<ol><li>Item i</li><li>Item ii</li></ol></li><li>Item B<ul><li>Item i</li></ul></li></ul></li><li>Item 2</li></ul>"
+    )
+  end
+
   test "<br> tags are separated by one new line" do
     assert_converted_to(
       "Hello world!\none\ntwo\nthree",