extended cat --ex and edit --ex to allow access to all levels of backtrace

cat --ex N   now shows a window of code around the Nth level of the backtrace (window size determined by Pry.config.exception_window_size, defaults to 5)
edit --ex N  opens an editor at the line of code at the Nth level of the backtrace

lib/pry/default_commands/introspection.rb

@@ -121,7 +121,7 @@ class Pry
             e.g: edit sample.rb
           USAGE
 
-          opt.on :e, :ex, "Open the file that raised the most recent exception (_ex_.file)"
+          opt.on :e, :ex, "Open the file that raised the most recent exception (_ex_.file)", :optional => true, :as => Integer
           opt.on :t, :temp, "Open an empty temporary file"
           opt.on :l, :line, "Jump to this line in the opened file", true, :as => Integer
           opt.on :n, :"no-reload", "Don't automatically reload the edited code"
@@ -162,14 +162,17 @@ class Pry
         else
           if opts.ex?
             next output.puts "No Exception found." if _pry_.last_exception.nil?
+            ex = _pry_.last_exception
+            bt_index = opts[:ex].to_i
 
-            if is_core_rbx_path?(_pry_.last_exception.file)
-              file_name = rbx_convert_path_to_full(_pry_.last_exception.file)
+            ex_file, ex_line = ex.bt_source_location_for(bt_index)
+            if is_core_rbx_path?(ex_file)
+              file_name = rbx_convert_path_to_full(ex_file)
             else
-              file_name = _pry_.last_exception.file
+              file_name = ex_file
             end
 
-            line = _pry_.last_exception.line
+            line = ex_line
             next output.puts "Exception has no associated file." if file_name.nil?
             next output.puts "Cannot edit exceptions raised in REPL." if Pry.eval_path == file_name
 

lib/pry/default_commands/shell.rb

@@ -38,6 +38,7 @@ class Pry
         start_line = 0
         end_line = -1
         file_name = nil
+        bt_index = 0
 
         opts = Slop.parse!(args) do |opt|
           opt.on :s, :start, "Start line (defaults to start of file)Line 1 is the first line.", true, :as => Integer do |line|
@@ -48,17 +49,19 @@ class Pry
             end_line = line - 1
           end
 
-          opt.on :ex, "Show a window of N lines either side of the last exception (defaults to 5).", :optional => true, :as => Integer do |window_size|
-            window_size ||= 5
+          opt.on :ex, "Show a window of N lines either side of the last exception (defaults to 5).", :optional => true, :as => Integer do |bt_index_str|
+            window_size = Pry.config.exception_window_size || 5
+            bt_index = bt_index_str.to_i
             ex = _pry_.last_exception
             next if !ex
-            start_line = (ex.line - 1) - window_size
+            ex_file, ex_line = ex.bt_source_location_for(bt_index)
+            start_line = (ex_line - 1) - window_size
             start_line = start_line < 0 ? 0 : start_line
-            end_line = (ex.line - 1) + window_size
-            if is_core_rbx_path?(ex.file)
-              file_name = rbx_convert_path_to_full(ex.file)
+            end_line = (ex_line - 1) + window_size
+            if is_core_rbx_path?(ex_file)
+              file_name = rbx_convert_path_to_full(ex_file)
             else
-              file_name = ex.file
+              file_name = ex_file
             end
           end
 
@@ -92,11 +95,12 @@ class Pry
 
         # add the arrow pointing to line that caused the exception
         if opts.ex?
+          ex_file, ex_line = _pry_.last_exception.bt_source_location_for(bt_index)
           contents = text.with_line_numbers contents, start_line + 1, :bright_red
 
           contents = contents.lines.each_with_index.map do |line, idx|
             l = idx + start_line
-            if l == (_pry_.last_exception.line - 1)
+            if l == (ex_line - 1)
               " =>#{line}"
             else
               "   #{line}"
@@ -105,7 +109,7 @@ class Pry
 
           # header for exceptions
           output.puts "\n#{Pry::Helpers::Text.bold('Exception:')} #{_pry_.last_exception.class}: #{_pry_.last_exception.message}\n--"
-          output.puts "#{Pry::Helpers::Text.bold('From:')} #{file_name} @ line #{_pry_.last_exception.line}\n\n"
+          output.puts "#{Pry::Helpers::Text.bold('From:')} #{ex_file} @ line #{ex_line} @ #{text.bold('level: ')} #{bt_index} of backtrace.\n\n"
         end
 
         set_file_and_dir_locals(file_name)

lib/pry/pry_class.rb

@@ -182,6 +182,7 @@ class Pry
     config.prompt = DEFAULT_PROMPT
     config.print = DEFAULT_PRINT
     config.exception_handler = DEFAULT_EXCEPTION_HANDLER
+    config.exception_window_size = 5
     config.hooks = DEFAULT_HOOKS
     config.color = true
     config.pager = true

lib/pry/pry_instance.rb

@@ -347,10 +347,13 @@ class Pry
   def set_last_exception(ex, target)
     class << ex
       attr_accessor :file, :line
+      def bt_source_location_for(index)
+        backtrace[index] =~ /(.*):(\d+)/
+        [$1, $2.to_i]
+      end
     end
 
-    ex.backtrace.first =~ /(.*):(\d+)/
-    ex.file, ex.line = $1, $2.to_i
+    ex.file, ex.line = ex.bt_source_location_for(0)#_btw_index#$1, $2.to_i
 
     @last_result_is_exception = true
     @output_array << ex