This is a complemantry repo for my talk Build a mini Ruby debugger in under 300 lines.
bundle install
break- list all breakpoints.break <line>- add a breakpoint at<line>of the current file.break <file>:<line>- add a breakpoint at the specified location.
delete <id>- delete the specified breakpoint.step- step in. Continue the program until the next stoppable point.next- step over. Continue the program until the next line.continue- continue the program.exit- exit the program.
Debug a script with $ bundle exec exe/debug app.rb
$ bundle exec exe/debug app.rb
Suspended by: Breakpoint at app.rb:1
[1, 6] in app.rb
=> 1| def fib(num)
2| if num < 2
3| num
4| else
5| fib(num-1) + fib(num-2)
6| end
(debug) break 5
Breakpoint added: app.rb:5
(debug) continue
Suspended by: Breakpoint at app.rb:5
[1, 10] in app.rb
1| def fib(num)
2| if num < 2
3| num
4| else
=> 5| fib(num-1) + fib(num-2)
6| end
7| end
8|
9| a = fib(6)
10| b = fib(7)
(debug)
To many Ruby devs, a more familiar usage would be adding breakpoints directly in the program, like binding.pry or binding.irb.
This debugger comes with binding.debug for such usages too:
require "debugger"
def fib(num)
if num < 2
num
else
binding.debug
fib(num-1) + fib(num-2)
end
end
a = fib(6)
b = fib(7)
puts a + b$ bundle exec ruby app.rb
[3, 12] in app.rb
3| def fib(num)
4| if num < 2
5| num
6| else
=> 7| binding.debug
8| fib(num-1) + fib(num-2)
9| end
10| end
11|
12| a = fib(6)
(debug) next
[4, 13] in app.rb
4| if num < 2
5| num
6| else
7| binding.debug
=> 8| fib(num-1) + fib(num-2)
9| end
10| end
11|
12| a = fib(6)
13| b = fib(7)
(debug)