Iex pry going step by step?

Question

I want to use IEx.pry to go step by step in my elixir code, like byebug in ruby or debug point in Java. I tried looking into the documentation here : https://github.com/elixir-lang/elixir/blob/4f68c4f10502e0f54a21093bb9a33957e63a9ac4/lib/iex/lib/iex.ex but did not find anything. Could anyone suggest a way to do this ?

Spicebush

Maybe you will find this useful: github.com/qhool/quaff – Utas

@PatrickOscity, I usually work on a remote machine. Is there a way to run the quaff tool in command line only ? – Spicebush

@VoodooChild: You can use ssh -Y when you ssh into your remote machine so any window will be redirected to your host machine. – Horlacher

Answer 1

It is not possible as pry is not a debugger. Pry simply allows you to interact with a particular context.

Domeniga

If pry isn't the answer to setting a breakpoint and stepping through a running Elixir program, what is? – Perorate

@Perorate , as Patrick pointed out, github.com/qhool/quaff is a tool which you can use – Spicebush

Can't believe I did not know about quaff until now. Thansk @Perorate – Gob

Answer 2

I was hoping for a way to step through Elixir code via IEx.pry as well, but that's not possible. Erlang does have a debugger that you can use for Elixir code.

You can start the debugger by running: :debugger.start()

I learned about it here: http://blog.plataformatec.com.br/2016/04/debugging-techniques-in-elixir-lang/

Spang

Answer 3

As the other answers pointed out, pry does not offer this functionality.

As a workaround you could add multiple IEx.pry instructions, inspect and use continue to go to the next one.

Sibyls

continue is used to continue the execution, the question is about step functionality. – Geophysics

Answer 4

After elixir 1.14, you can use the next/0 function after setting a breakpoint on the function you wanna debug.

To se a breakpoint you need to enter your iex terminal and use the function break!/2 and pass the function and the arity, so said function receives a breakpoint. Like this:

break! MyModule.function_to_be_debugged/2

And then, when you call said function, you will be able to debug it, line by line with the next/0

Chintzy