Normalize zipnote filename diff ordering

app/models/job.rb

@@ -49,10 +49,41 @@ def details
     result.to_unified_diff
   end
 
+  def normalize_zipnote_diffs(diff)
+    normalize_diff_details(diff)
+    diff
+  end
+
+  def normalize_diff_details(detail)
+    detail["details"]&.each { |subdetail| normalize_diff_details(subdetail) }
+
+    return unless detail["unified_diff"].present?
+    return unless [detail["source1"], detail["source2"]].compact.any? { |source| source.include?("zipnote") }
+
+    detail["unified_diff"] = sort_zipnote_filename_diff(detail["unified_diff"])
+  end
+
+  def sort_zipnote_filename_diff(diff)
+    filename_lines, other_lines = diff.lines.partition do |line|
+      line.start_with?("-Filename: ") || line.start_with?("+Filename: ")
+    end
+
+    removed = filename_lines.select { |line| line.start_with?("-Filename: ") }.sort_by { |line| zipnote_sort_key(line) }
+    added = filename_lines.select { |line| line.start_with?("+Filename: ") }.sort_by { |line| zipnote_sort_key(line) }
+
+    return diff if removed.empty? || added.empty? || removed.length != added.length
+
+    removed.zip(added).flat_map { |old_line, new_line| [old_line, new_line] }.join + other_lines.join
+  end
+
+  def zipnote_sort_key(line)
+    line.sub(/^[+-]Filename: /, '').sub(%r{^[^/]+/}, '')
+  end
+
   def generate_diff
     result = Diffoscope.compare(url_1, url_2, new_file: true)
     update!(
-      results: { diff: result.to_h },
+      results: { diff: normalize_zipnote_diffs(result.to_h) },
       status: 'complete',
       sha256_1: result.sha256_1,
       sha256_2: result.sha256_2

test/models/job_test.rb

@@ -22,6 +22,22 @@ class JobTest < ActiveSupport::TestCase
     @job.generate_diff_async
   end
 
+  test 'normalize_zipnote_diffs sorts zipnote filename entries recursively' do
+    diff = {
+      "details" => [
+        {
+          "source1" => "zipnote {}",
+          "source2" => "zipnote {}",
+          "unified_diff" => "-Filename: pkg@v1/z.yml\n+Filename: pkg@v2/a.yml\n-Filename: pkg@v1/a.yml\n+Filename: pkg@v2/z.yml\n Comment:\n"
+        }
+      ]
+    }
+
+    @job.normalize_zipnote_diffs(diff)
+
+    assert_equal "-Filename: pkg@v1/a.yml\n+Filename: pkg@v2/a.yml\n-Filename: pkg@v1/z.yml\n+Filename: pkg@v2/z.yml\n Comment:\n", diff["details"].first["unified_diff"]
+  end
+
   test 'generate_diff' do
     result = mock
     result.stubs(:to_h).returns({ "source1" => "a", "source2" => "b" })