With to case rewrite fails with else stab `(_ -> "")`

[iamhassangm]

Description

When trying to format code containing the pattern (_ -> ""), Styler 1.3.3 crashes with a FunctionClauseError.

Environment

• Elixir: 1.18.1
• Styler: 1.3.3

Error Message

** (FunctionClauseError) no function clause matching in Enum."-reduce/3-lists^foldl/2-0-"/3

    The following arguments were given to Enum."-reduce/3-lists^foldl/2-0-"/3:

        # 1
        #Function<44.12736194/2 in Code.Formatter.traverse_line>

        # 2
        {1, 456}

        # 3
        {:__block__, [closing: [line: 457], line: 457], [[{:->, [line: 457], [[{:_, [line: 457], nil}], {:__block__, [delimiter: "\"", line: 457], [""]}]}]]}

Minimal Example

with :ok <- can(current_user, _, _),
         do: email,
         else: (_ -> "")

Expected Behavior

The formatter should handle this valid Elixir syntax without crashing.

Actual Behavior

The formatter crashes with a FunctionClauseError when attempting to format this code.

[novaugust]

hey @iamhassangm , thanks for the issue.

this was a bug in elixir in 1.17 that was supposed to be resolved for 1.18. i'll get a repro and bring it up with the elixir folks

[novaugust]

@iamhassangm With the test case you gave me, I get a different error than the one you're seeing.

** (Protocol.UndefinedError) protocol Enumerable not implemented for type Tuple. This protocol is implemented for the following type(s): Date.Range, File.Stream, Function, GenEvent.Stream, HashDict, HashSet, IO.Stream, List, Map, MapSet, Range, Stream

i'll look into fixing that to see if it also fixes your problem, but do you have different code you could share to recreate your exact issue?

[novaugust]

since we had different exceptions, let me know if that fix doesn't work for you. hopefully it does 🤞

[iamhassangm]

Yes, it solved my problem.
Thank you very much for the prompt fix!

[ice-cap0]

on my end, it's currently formatting

  else: (_err -> {:error, :timeslot_unavailable})

to

  else: ->(_err, {:error, :timeslot_unavailable})

[novaugust]

Hey @ice-cap0 , it's helpful if you list your elixir version, styler version, etc.

You're probably experiencing a bug in elixir 1.17. go to 1.18 for the fix
#217

[ice-cap0]

I actually migrated to 1.18 before reporting the issue :)

i'm on elixir 1.18.2, styler 1.4

[novaugust]

@ice-cap0 make a new issue with code i can reproduce from? couldn't extrapolate a repro from that snippet

[ice-cap0]

can't reproduce anymore actually, not sure what happened
works fine now :)