Allow variables defined in doctests to be used in expectation (#12730)

Author: rich

lib/ex_unit/lib/ex_unit/doc_test.ex

@@ -382,9 +382,15 @@ defmodule ExUnit.DocTest do
     last_expr = Macro.to_string(last_expr(expr_ast))
 
     quote do
+      # `expr_ast` may introduce variables that may be
+      # used within `expected_ast` so they both need to
+      # unquoted together here
+      value = unquote(expr_ast)
+      expected_value = unquote(expected_ast)
+
       ExUnit.DocTest.__test__(
-        unquote(expr_ast),
-        unquote(expected_ast),
+        value,
+        expected_value,
         unquote(doctest),
         unquote(last_expr),
         unquote(expected),

lib/ex_unit/test/ex_unit/doc_test_test.exs

@@ -443,6 +443,16 @@ defmodule ExUnit.DocTestTest.Haiku do
 end
 |> ExUnit.BeamHelpers.write_beam()
 
+defmodule ExUnit.DocTestTest.VariableInExpectation do
+  @doc """
+  iex> num = 1
+  iex> ExUnit.DocTestTest.VariableInExpectation.inc(num)
+  num + 1
+  """
+  def inc(num), do: num + 1
+end
+|> ExUnit.BeamHelpers.write_beam()
+
 defmodule ExUnit.DocTestTest.PatternMatching do
   def starting_line, do: __ENV__.line + 2
 
@@ -506,6 +516,7 @@ defmodule ExUnit.DocTestTest do
   doctest ExUnit.DocTestTest.IndentationHeredocs
   doctest ExUnit.DocTestTest.FencedHeredocs
   doctest ExUnit.DocTestTest.Haiku
+  doctest ExUnit.DocTestTest.VariableInExpectation
 
   import ExUnit.CaptureIO