lua_error.rb in wolverine-0.3.5

- old
+ new

@@ -5,11 +5,14 @@
   # modifies the backtrace to include the lua script itself in a reasonable
   # way.
   class LuaError < StandardError
     PATTERN = /ERR Error (compiling|running) script \(.*?\): .*?:(\d+): (.*)/
     WOLVERINE_LIB_PATH = File.expand_path('../../', __FILE__)
+    CONTEXT_LINE_NUMBER = 2
 
+    attr_reader :error, :file, :content
+
     # Is this error one that should be reformatted?
     #
     # @param error [StandardError] the original error raised by redis
     # @return [Boolean] is this an error that should be reformatted?
     def self.intercepts? error
@@ -19,21 +22,37 @@
     # Initialize a new {LuaError} from an existing redis error, adjusting
     # the message and backtrace in the process.
     #
     # @param error [StandardError] the original error raised by redis
     # @param file [Pathname] full path to the lua file the error ocurred in
-    def initialize error, file
+    # @param content [String] lua file content the error ocurred in
+    def initialize error, file, content
       @error = error
       @file = file
+      @content = content
 
       @error.message =~ PATTERN
-      stage, line_number, message = $1, $2, $3
+      _stage, line_number, message = $1, $2, $3
+      error_context = generate_error_context(content, line_number.to_i)
 
-      super message
+      super "#{message}\n\n#{error_context}\n\n"
       set_backtrace generate_backtrace file, line_number
     end
 
     private
+
+    def generate_error_context(content, line_number)
+      lines = content.lines.to_a
+      beginning_line_number = [1, line_number - CONTEXT_LINE_NUMBER].max
+      ending_line_number = [lines.count, line_number + CONTEXT_LINE_NUMBER].min
+      line_number_width = ending_line_number.to_s.length
+
+      (beginning_line_number..ending_line_number).map do |number|
+        indicator = number == line_number ? '=>' : '  '
+        formatted_number = "%#{line_number_width}d" % number
+        " #{indicator} #{formatted_number}: #{lines[number - 1]}"
+      end.join.chomp
+    end
 
     def generate_backtrace(file, line_number)
       pre_wolverine = backtrace_before_entering_wolverine(@error.backtrace)
       index_of_first_wolverine_line = (@error.backtrace.size - pre_wolverine.size - 1)
       pre_wolverine.unshift(@error.backtrace[index_of_first_wolverine_line])