add exit/quit hint

[simonbyrne]

By changing the show method, we can provide more useful hints (this idea is gratuitously stolen from Python):

julia> exit
Use exit(), quit() or Ctrl-D to exit

[yuyichao]

Can this be more repl specific?

[simonbyrne]

Probably, but I still don't really understand how display works...

[yuyichao]

I'm actually talking about something more integrated into the REPL (since that's where we need this) instead of modifying how some functions are displayed.

Something like

diff --git a/base/REPL.jl b/base/REPL.jl
index 7a4eb61b46..5ac8261dfc 100644
--- a/base/REPL.jl
+++ b/base/REPL.jl
@@ -138,7 +138,9 @@ function print_response(errio::IO, val::ANY, bt, show_value::Bool, have_color::B
                                                           errio, QuoteNode(val), bt))))
                 iserr, lasterr = false, ()
             else
-                if val !== nothing && show_value
+                if (val === exit || val === quit) && show_value && specialdisplay === nothing
+                    println("Use exit(), quit() or Ctrl-D to exit")
+                elseif val !== nothing && show_value
                     try
                         if specialdisplay === nothing
                             eval(Main, Expr(:body, Expr(:return, Expr(:call, display, QuoteNode(val)))))

This gives;

julia> exit
Use exit(), quit() or Ctrl-D to exit

julia> quit
Use exit(), quit() or Ctrl-D to exit

julia> print(exit)
exit
julia> display(exit)
exit (generic function with 2 methods)

julia> display(quit)
quit (generic function with 1 method)

Ideally we may want to do this only when the input is just quit and exit.

When trying this I realized that this will make it harder to see how many methods are defined for the two function. Hopefully it's fine...

[JeffBezanson]

I completely agree --- this should only be an interactive feature, if anything, not something that prevents you from normally showing certain functions.

[stevengj]

This is one of the rare cases where you might want to overload display:

Base.display(d::Base.REPL.REPLDisplay, ::Union{typeof(exit),typeof(quit)}) = display(d, Text("Use exit(), quit(), or Ctrl-D to exit"))

will work and should only affect output in the REPL, and doesn't require hacking REPL internals.

[yuyichao]

I didn't overload display because this way we can probably pass in additional information and only show it on certain inputs.

[JeffBezanson]

This should not affect how the object is shown, it should only affect the exact input exit, not e.g. fs = [exit]; fs[1].

[yuyichao]

Yeah, agree. print_response is just easier to find then the input handling ;-p

[omus]

Is there a reason we're not doing exit(n=0) = ...?

[stevengj]

Probably this function pre-dates optional arguments.

[JeffBezanson]

I hate special cases like this, but could maybe tolerate it if it were REPL-only. 👎

[musm]

closed in favor of #38522