feat: add sigil support for module attribute formatting (#9)

Adds comprehensive support for formatting markdown content within ~S and
~s sigils in module attributes with all delimiter types and proper
formatting preservation.

Author: fahchen

README.md

@@ -25,7 +25,7 @@ Add to your `mix.exs`:
 ```elixir
 def deps do
   [
-    {:dprint_markdown_formatter, "~> 0.4.0"}
+    {:dprint_markdown_formatter, "~> 0.5.0"}
   ]
 end
 ```

lib/dprint_markdown_formatter/ast_processor.ex

@@ -95,6 +95,27 @@ defmodule DprintMarkdownFormatter.AstProcessor do
           acc
         )
 
+      # Handle sigil patterns: @moduledoc ~S"""content""" or @moduledoc ~s/content/
+      {:@, _meta,
+       [
+         {attr, _attr_meta,
+          [
+            {sigil_type, sigil_meta,
+             [{:<<>>, _binary_meta, [doc_content]} = binary_node, _modifiers]} =
+                sigil_node
+          ]}
+       ]}
+      when is_atom(attr) and is_binary(doc_content) and sigil_type in [:sigil_S, :sigil_s] ->
+        process_sigil_doc_attribute(
+          node,
+          attr,
+          doc_content,
+          %{sigil: sigil_node, binary: binary_node, type: sigil_type, meta: sigil_meta},
+          doc_attributes,
+          nif_config,
+          acc
+        )
+
       _other_node ->
         {node, acc}
     end
@@ -148,6 +169,67 @@ defmodule DprintMarkdownFormatter.AstProcessor do
     end
   end
 
+  defp process_sigil_doc_attribute(
+         node,
+         attr,
+         doc_content,
+         %{sigil: sigil_node, binary: binary_node, type: sigil_type, meta: sigil_meta},
+         doc_attributes,
+         nif_config,
+         acc
+       ) do
+    if attr in doc_attributes do
+      case format_markdown_content(doc_content, nif_config) do
+        {:ok, formatted} when formatted != doc_content ->
+          create_patch_for_formatted_sigil_content(
+            node,
+            formatted,
+            sigil_node,
+            binary_node,
+            sigil_type,
+            sigil_meta,
+            acc
+          )
+
+        {:ok, _unchanged} ->
+          {node, acc}
+
+        {:error, _error} ->
+          {node, acc}
+      end
+    else
+      {node, acc}
+    end
+  end
+
+  defp create_patch_for_formatted_sigil_content(
+         node,
+         formatted,
+         sigil_node,
+         _binary_node,
+         sigil_type,
+         sigil_meta,
+         acc
+       ) do
+    range = Sourceror.get_range(sigil_node)
+    delimiter = sigil_meta[:delimiter]
+
+    sigil_prefix =
+      case sigil_type do
+        :sigil_S -> "~S"
+        :sigil_s -> "~s"
+      end
+
+    replacement = PatchBuilder.build_replacement_sigil_string(formatted, sigil_prefix, delimiter)
+
+    patch = %Sourceror.Patch{
+      range: range,
+      change: replacement
+    }
+
+    {node, [patch | acc]}
+  end
+
   defp format_markdown_content(content, nif_config) do
     case DprintMarkdownFormatter.Native.format_markdown(content, nif_config) do
       {:ok, formatted} ->

lib/dprint_markdown_formatter/patch_builder.ex

@@ -6,6 +6,8 @@ defmodule DprintMarkdownFormatter.PatchBuilder do
   replacements, supporting both simple strings and heredoc formats.
   """
 
+  @single_char_delimiters ["\"", "'", "/", "|", "(", "[", "{", "<"]
+
   @doc """
   Builds a replacement string for formatted content based on the original
   delimiter.
@@ -76,4 +78,68 @@ defmodule DprintMarkdownFormatter.PatchBuilder do
     # Heredoc format - preserve as heredoc
     "\"\"\"\n#{formatted}\n\"\"\""
   end
+
+  @doc """
+  Builds a replacement string for sigil content, preserving the original sigil
+  type and delimiter.
+
+  Handles all supported sigil delimiters and maintains proper formatting for both
+  simple and heredoc-style sigils.
+
+  ## Examples
+
+      iex> DprintMarkdownFormatter.PatchBuilder.build_replacement_sigil_string("Hello", "~S", "\\"")
+      "~S\\"Hello\\""
+
+      iex> DprintMarkdownFormatter.PatchBuilder.build_replacement_sigil_string("Hello\\nWorld", "~S", "\\"\\"\\\"")
+      "~S\\"\\"\\\"\\nHello\\nWorld\\n\\"\\"\\""
+
+      iex> DprintMarkdownFormatter.PatchBuilder.build_replacement_sigil_string("Hello", "~s", "/")
+      "~s/Hello/"
+  """
+  @spec build_replacement_sigil_string(String.t(), String.t(), String.t()) :: String.t()
+  def build_replacement_sigil_string(formatted, sigil_prefix, delimiter) do
+    case delimiter do
+      "\"\"\"" ->
+        # Heredoc sigil - format exactly like regular heredocs
+        "#{sigil_prefix}\"\"\"\n#{formatted}\n\"\"\"\n"
+
+      "'''" ->
+        # Triple single quote heredoc - same as triple double quotes
+        "#{sigil_prefix}'''\n#{formatted}\n'''\n"
+
+      single_delimiter when single_delimiter in @single_char_delimiters ->
+        # Single character delimiters - preserve original delimiter structure
+        closing_delimiter = get_closing_delimiter(single_delimiter)
+
+        # For simple delimiters, match the expected format precisely
+        # Single-line sigils should not have trailing newline
+        # Multi-line sigils should have newline after closing delimiter
+        has_newlines = String.contains?(formatted, "\n")
+
+        if has_newlines do
+          # Multi-line content needs newline after closing delimiter
+          "#{sigil_prefix}#{single_delimiter}\n#{formatted}\n#{closing_delimiter}\n"
+        else
+          # Single-line content - no trailing newline
+          "#{sigil_prefix}#{single_delimiter}#{formatted}#{closing_delimiter}"
+        end
+
+      _unknown_delimiter ->
+        # Fallback to heredoc for unknown delimiters
+        "#{sigil_prefix}\"\"\"\n#{formatted}\n\"\"\"\n"
+    end
+  end
+
+  # Private helper to get the closing delimiter for bracket-style delimiters
+  defp get_closing_delimiter(opening) do
+    case opening do
+      "(" -> ")"
+      "[" -> "]"
+      "{" -> "}"
+      "<" -> ">"
+      # For quotes, slashes, pipes - closing is same as opening
+      other -> other
+    end
+  end
 end

llms.txt

@@ -21,7 +21,7 @@ Add to `mix.exs`:
 ```elixir
 def deps do
   [
-    {:dprint_markdown_formatter, "~> 0.4.0"}
+    {:dprint_markdown_formatter, "~> 0.5.0"}
   ]
 end
 ```

mix.exs

@@ -1,7 +1,7 @@
 defmodule DprintMarkdownFormatter.MixProject do
   use Mix.Project
 
-  @version "0.4.0"
+  @version "0.5.0"
   @source_url "https://github.com/fahchen/dprint_markdown_formatter"
 
   def project do