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REPL-only: Print a hint if the user types exit in the REPL #38522

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REPL-only: Print a hint if the user types exit in the REPL #38522

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REPL-only: Print a hint if the user types `exit` in the REPL
DilumAluthge Mar 17, 2021
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DilumAluthge Apr 16, 2021
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11 changes: 11 additions & 0 deletions stdlib/REPL/src/REPL.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -370,6 +370,7 @@ function run_frontend(repl::BasicREPL, backend::REPLBackendRef)
if !isempty(line)
response = eval_with_backend(ast, backend)
print_response(repl, response, !ends_with_semicolon(line), false)
print_exit_hint(repl, line)
end
write(repl.terminal, '\n')
((!interrupted && isempty(line)) || hit_eof) && break
Expand Down Expand Up @@ -796,6 +797,7 @@ function respond(f, repl, main; pass_empty::Bool = false, suppress_on_semicolon:
end
hide_output = suppress_on_semicolon && ends_with_semicolon(line)
print_response(repl, response, !hide_output, hascolor(repl))
print_exit_hint(repl, line)
end
prepare_next(repl)
reset_state(s)
Expand Down Expand Up @@ -1224,6 +1226,7 @@ function run_frontend(repl::StreamREPL, backend::REPLBackendRef)
end
response = eval_with_backend(ast, backend)
print_response(repl, response, !ends_with_semicolon(line), have_color)
print_exit_hint(repl, line)
end
end
# Terminate Backend
Expand All @@ -1232,4 +1235,12 @@ function run_frontend(repl::StreamREPL, backend::REPLBackendRef)
nothing
end

print_exit_hint(repl::AbstractREPL, line) = print_exit_hint(outstream(repl), line)
function print_exit_hint(io::IO, line)
if lowercase(strip(line)) == "exit"
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Would it make sense to also print this if the input is "quit" (that's what e.g. GAP uses) ?

Anyway, I really like this PR, it fixes one of those tiny papercuts which seem irrelevant in isolation but add up.

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I wouldn't object to also doing this for "quit", but I'll defer to @JeffBezanson.

I'd want to keep this limited to a very small set of inputs. For example, you can exit R by typing q() and pressing enter. But I definitely wouldn't want to print a hint if someone types q in the Julia REPL.

I think it makes sense for exit because the corresponding function exit() is a function that actually exists in Julia. But we don't actually have a quit function in Julia.

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But I don't feel strongly either way. Happy to add quit, also happy to leave it out.

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Yes I think we should add it.

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I like what the python repl does:

>>> quit
Use quit() or Ctrl-D (i.e. EOF) to exit
>>> quit = 2
>>> quit
2

It stops printing the message if quit is defined as a variable. Stylish! I think we should do this too.
Can be checked with Base.isbindingresolved(Main, :exit) && isdefined(Main, :exit).

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In python, that's not magic, it is just literally the definition of show for that default variable:

>>> exit.__class__
<class 'site.Quitter'>
>>> quit.__class__
<class 'site.Quitter'>

The equivalent here would be:

julia> using Base: exit as quit; # @eval Base const quit = exit; @eval Base export quit;

julia> Base.show(io::IO, ::MIME"text/plain", ::typeof(exit)) = print(io, "Use exit() or Ctrl-D (i.e. EOF) to quit")

julia> repr(exit)
"exit"

julia> show(exit)
exit
julia> summary(exit)
"typeof(exit)"

julia> display(exit)
Use exit() or Ctrl-D (i.e. EOF) to quit

julia> exit
Use exit() or Ctrl-D (i.e. EOF) to quit

julia> exit()

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Which would have been #21362

println(io, "\nTo exit Julia, use Ctrl-D, or type exit() and press enter.")
end
return nothing
end

end # module