[Proposal] `IO.inspect_vars/1`

[Myron Marston]

IO.inspect has long been my go-to technique for troubleshooting code that isn’t quite working how I would expect. Since the :label option was added in 1.4, I use that all the time, too. The majority of the time, I use it to inspect one or more variables like so:

IO.inspect(foo, label: "foo")
IO.inspect(bar, label: "bar")

However, I often find my self making simple, dumb mistakes when setting this up, such as copying and pasting a prior IO.inspect line, but forgetting to update the label, e.g.:

IO.inspect(foo, label: "foo")
IO.inspect(bar, label: "foo") # woops, the output will label this as `foo`, too!

Given how common this pattern is, it would be really nice if there was a function or macro to do this for us. I’m thinking something like:

# inspect each variable in the current scope, labeling each with its name
IO.inspect_vars(:all)

# inspect just the provided variables, labeling each
IO.inspect_vars([foo, bar])

# inspect all variables in the current scope, except the provided ones, labeling each
IO.inspect_vars(except: [foo, bar])

I can also imagine it supporting a label option, to put a title above the list of variables, in order to distinguish multiple variable reports.

Would others find this as useful as I would? Is there interest in it being added to Elixir?

Thanks!
Myron

​

[José Valim]

I use IO.inspect(binding()) a lot.

Although I don't think IO.inspect_vars would be a thing since it would need to be a macro and having to require it before would probably lose its appeal (and we don't plan to require anything other than Kernel by default).

José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

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[Myron Marston]

I never knew about `binding/0`.  Thanks for the tip; `IO.inspect(binding())` definitely does the kind of thing I'm looking for.

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