Debugger improvement: don't print result of a step to string

[DesmondHayes]

Consider an example:

(defn foo [x y]
  (symbol (str x "/" y)))

I want to debug the following call to 'foo:

(foo "bar" "baz")

Debugger step results as I press "n":

N	Now (bad)	Should be (good)
1	""bar""	"bar"
2	""baz""	"baz"
3	""bar/baz""	"bar/baz"
4	"bar/baz"	bar/baz

[Malabarba]

Thanks for the report. I'll look into this.

[cichli]

@Malabarba nREPL already does the equivalent of pr-str on :value slots in responses (see this middleware), so I think we're double-printing. This likely only happens with more recent versions of nREPL (>= 0.27) due to a change in the middleware ordering algorithm in 0.2.7. We have a few options:

• Include a non-nil value in the :printed-value slot of the response, so pr-values will skip printing
• Keep doing the printing ourselves in the debugger middleware but use a different slot name than :value
• Remove the call to pr-str from the debugger middleware, and add #'pr-values to the :requires set of wrap-debug, to guarantee that the slot will be printed (like here)

:printed-value was only added to nREPL 0.2.10, and pr-values is technically an nREPL implementation detail, so maybe option 2 is the simplest. Thoughts?

[Malabarba]

I added the manual printing because it seemed to be necessary on the
nrepl version I had. Otherwise I ran into issues. I think my version
was 0.2.6, so it's consistent with what you're saying, @cichli.

And yes, I think option 2 is the simplest.