Respect extra_failure_lines in RSpec metadata

lib/super_diff/rspec/monkey_patches.rb

@@ -218,7 +218,10 @@ def failure_line_groups
                   }
                 end
               end
-
+              @failure_line_groups << {
+                lines: extra_failure_lines,
+                already_colorized: true
+              }
               @failure_line_groups
             end
           end
@@ -241,6 +244,24 @@ def failure_slash_error_lines
             lines
           end
 
+          # Override to ensure that each item in the array returned is one and
+          # only one line and doesn't contain any newline characters
+          def extra_failure_lines
+            @extra_failure_lines ||=
+              begin
+                original_lines = Array(example.metadata[:extra_failure_lines])
+                normalized_lines =
+                  original_lines.flat_map { |line| line.split("\n") }
+                unless normalized_lines.empty?
+                  unless normalized_lines.first == ""
+                    normalized_lines.unshift("")
+                  end
+                  normalized_lines.push("") unless normalized_lines.last == ""
+                end
+                normalized_lines
+              end
+          end
+
           # Exclude this file from being included in backtraces, so that the
           # SnippetExtractor prints the right thing
           def find_failed_line

spec/integration/rspec/magic_metadata_spec.rb

@@ -0,0 +1,51 @@
+require "spec_helper"
+
+RSpec.describe "Integration with RSpec's magic metadata", type: :integration do
+  it "includes extra_failure_lines in failure messages" do
+    as_both_colored_and_uncolored do |color_enabled|
+      snippet = <<~TEST.strip
+          RSpec.describe "test" do
+            it { expect(true).to be(false) }
+
+            after do
+              RSpec.current_example.metadata[:extra_failure_lines] = "foo\nbar"
+            end
+          end
+        TEST
+      program =
+        make_plain_test_program(
+          snippet,
+          color_enabled: color_enabled,
+          preserve_as_whole_file: true
+        )
+
+      expected_output =
+        build_expected_output(
+          color_enabled: color_enabled,
+          test_name: "test is expected to equal false",
+          snippet: "it { expect(true).to be(false) }",
+          expectation:
+            proc do
+              line do
+                plain "Expected "
+                actual "true"
+                plain " to equal "
+                expected "false"
+                plain "."
+              end
+            end,
+          extra_failure_lines:
+            proc do
+              indent by: 5 do
+                line "foo"
+                line "bar"
+              end
+            end
+        )
+
+      expect(program).to produce_output_when_run(expected_output).in_color(
+        color_enabled
+      )
+    end
+  end
+end

spec/support/integration/helpers.rb

@@ -48,15 +48,17 @@ def build_expected_output(
       color_enabled:,
       snippet:,
       expectation:,
+      test_name: "test passes",
       key_enabled: true,
       newline_before_expectation: false,
       indentation: 7,
-      diff: nil
+      diff: nil,
+      extra_failure_lines: nil
     )
       colored(color_enabled: color_enabled) do
         line "Failures:\n"
 
-        line "1) test passes", indent_by: 2
+        line "1) #{test_name}", indent_by: 2
 
         line indent_by: 5 do
           bold "Failure/Error: "
@@ -106,6 +108,11 @@ def build_expected_output(
             newline
           end
         end
+
+        if extra_failure_lines
+          newline
+          evaluate_block(&extra_failure_lines)
+        end
       end
     end