Support exceptions in results

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Support parsing multiline doctests with `iex>` on all lines, but reformat them using `...>` on every line but the first one.
 - Fix implementation for multiline results. Multiline results are allowed, and they can be terminated with an empty new line or another doctest.
+- Support exception expressions (`** (ModuleName) message`) in results.
 
 ## 0.1.0 (2024-02-25)
 

lib/doctest_formatter/formatter.ex

@@ -90,16 +90,31 @@ defmodule DoctestFormatter.Formatter do
         Indentation.indent(symbol <> line, chunk.indentation)
       end)
 
-    formatted_result =
+    string_result =
       chunk.result
       |> Enum.join("\n")
-      |> Code.format_string!(opts)
-      |> IO.iodata_to_binary()
+
+    string_result =
+      if exception_result?(string_result) do
+        string_result
+        |> String.trim()
+      else
+        string_result
+        |> Code.format_string!(opts)
+        |> IO.iodata_to_binary()
+      end
+
+    formatted_result =
+      string_result
       |> String.split("\n")
       |> Enum.map(fn line ->
         Indentation.indent(line, chunk.indentation)
       end)
 
     formatted_lines ++ formatted_result
   end
+
+  defp exception_result?(string) do
+    string |> String.trim() |> String.starts_with?("** (")
+  end
 end

smoke_test_data/elixir-1-13/project_with_formatted_code/lib/project_with_formatted_code.ex

@@ -18,6 +18,9 @@ defmodule ProjectWithFormattedCode do
       ...> |> ProjectWithFormattedCode.add(2)
       3
 
+      iex> 3 + "3"
+      ** (ArithmeticError) bad argument in arithmetic expression
+
   """
   def add(a, b) do
     a + b

smoke_test_data/project_with_formatted_code/lib/project_with_formatted_code.ex

@@ -18,6 +18,9 @@ defmodule ProjectWithFormattedCode do
       ...> |> ProjectWithFormattedCode.add(2)
       3
 
+      iex> 3 + "3"
+      ** (ArithmeticError) bad argument in arithmetic expression
+
   """
   def add(a, b) do
     a + b

test/doctest_formatter/formatter_test.exs

@@ -676,6 +676,35 @@ defmodule DoctestFormatter.FormatterTest do
       output = format(input, opts)
       assert output == desired_output
     end
+
+    test "can handle exceptions in results" do
+      input =
+        """
+        defmodule Foo do
+          @doc \"""
+          iex>  "Fizz"
+          iex>   |> Kernel.<>( "Buzz" )
+          iex> |>     Kernel.<>(nil)
+                   ** (ArgumentError) expected binary argument in <> operator but got: nil
+          \"""
+        end
+        """
+
+      desired_output =
+        """
+        defmodule Foo do
+          @doc \"""
+          iex> "Fizz"
+          ...> |> Kernel.<>("Buzz")
+          ...> |> Kernel.<>(nil)
+          ** (ArgumentError) expected binary argument in <> operator but got: nil
+          \"""
+        end
+        """
+
+      output = format(input, [])
+      assert output == desired_output
+    end
   end
 
   describe "format/2 on @moduledocs" do