Make gem work for projects with Ruby >= 2.7 and source code with UTF-8

lib/reverse_coverage/formatters/html/formatter.rb

@@ -58,13 +58,42 @@ def formatted_source_file(source_file)
         end
 
         def readfile(source_file)
-          File.open(filename(source_file), "rb", &:readlines)
+          load_source(filename(source_file))
+        end
+
+        def load_source(file_name)
+          lines = []
+          # The default encoding is UTF-8
+          File.open(file_name, "rb:UTF-8") do |file|
+            line = file.gets
+
+            # Check for shbang
+            if /\A#!/.match?(line)
+              lines << line
+              line = file.gets
+            end
+            return lines unless line
+
+            check_magic_comment(file, line)
+            lines.concat([line], file.readlines)
+          end
+
+          lines
+        end
+
+        def check_magic_comment(file, line)
+          # Check for encoding magic comment
+          # Encoding magic comment must be placed at first line except for shbang
+          if (match = /\A#\s*(?:-\*-)?\s*(?:en)?coding:\s*(\S+)\s*(?:-\*-)?\s*\z/.match(line))
+            file.set_encoding(match[1], "UTF-8")
+          end
         end
 
         def grouped(files)
           grouped = {}
           grouped_files = []
 
+          # TODO Someday / Maybe. Make this list configurable
           groups = {
             'Controllers' => %r{/app/controllers},
             'Channels' => %r{/app/channels},

lib/reverse_coverage/main.rb

@@ -29,10 +29,8 @@ def add(example)
         lines.each_with_index do |changed, line_index|
           next if changed.nil? || changed.zero?
 
-          file_info = { file_path: file_path, line_index: line_index }
-
-          save_changes(changes, example_data, file_info)
-          save_changes(coverage_matrix, example_data, file_info)
+          save_changes(changes, example_data, file_path: file_path, line_index: line_index)
+          save_changes(coverage_matrix, example_data, file_path: file_path, line_index: line_index)
         end
       end