REPL shows error when trying to tab-complete after undefined macro name like @undefined.<tab>

[nickrobinson251]

Tab-completing a name prefixed with @, like @undefined.<tab> shows an error, when i think ideally it would just do nothing. I ran into this when trying to type @Meta.dump and save myself those 4 extra keystrokes.

Here's a longer story, with example (using Julia v1.6.2):

In the REPL, you can tab-complete to get a list of accessible name e.g.

julia> Meta. # <tab> 
@dump                    is_meta_expr_head         parse
@lower                   isbinaryoperator          parseall
ParseError               isexpr                    parseatom
_instantiate_type_in_env isidentifier              partially_inline!
_parse_string            isoperator                quot
_partially_inline!       ispostfixoperator         replace_sourceloc!
eval                     isunaryoperator           sexpr_indent_width
include                  lower                     show_sexpr
julia> Meta.

And if you try to tab-complete after an undefined name, then nothing happens (well, the little julia> prompt will flash, which is cute and helpful, but there'l be no output)

julia> Nonexistant. # <tab> ...nothing happens

You can (unfortunately, in my view) spell macros like Meta.@dump as @Meta.dump

julia> Meta.@dump 1 + 2
Expr
  head: Symbol call
  args: Array{Any}((3,))
    1: Symbol +
    2: Int64 1
    3: Int64 2

julia> @Meta.dump 1 + 2
Expr
  head: Symbol call
  args: Array{Any}((3,))
    1: Symbol +
    2: Int64 1
    3: Int64 2

But if you combine these two things and try to tab-complete @Meta.<tab>, then a big ugly error message is shown:

julia> @Meta.┌ Error: Error in the keymap
│   exception =
│    LoadError: UndefVarError: @Meta not defined
│    Stacktrace:
│      [1] top-level scope
│        @ :0
│      [2] lower
│        @ ./meta.jl:165 [inlined]
│      [3] get_type(sym::Expr, fn::Module)
│        @ REPL.REPLCompletions /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPLCompletions.jl:459
│      [4] complete_symbol(sym::String, ffunc::REPL.REPLCompletions.var"#34#37", context_module::Module)
│        @ REPL.REPLCompletions /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPLCompletions.jl:153
│      [5] completions(string::String, pos::Int64, context_module::Module)
│        @ REPL.REPLCompletions /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPLCompletions.jl:774
│      [6] completions
│        @ /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPLCompletions.jl:638 [inlined]
│      [7] complete_line(c::REPL.REPLCompletionProvider, s::REPL.LineEdit.PromptState)
│        @ REPL /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPL.jl:439
│      [8] complete_line(s::REPL.LineEdit.PromptState, repeats::Int64)
│        @ REPL.LineEdit /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:348
│      [9] complete_line(s::REPL.LineEdit.MIState)
│        @ REPL.LineEdit /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:339
│     [10] edit_tab(s::REPL.LineEdit.MIState, jump_spaces::Bool, delete_trailing::Bool) (repeats 2 times)
│        @ REPL.LineEdit /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2118
│     [11] (::REPL.LineEdit.var"#109#162")(::REPL.LineEdit.MIState, ::Any, ::Vararg{Any, N} where N)
│        @ REPL.LineEdit /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2159
│     [12] #invokelatest#2
│        @ ./essentials.jl:708 [inlined]
│     [13] invokelatest
│        @ ./essentials.jl:706 [inlined]
│     [14] (::REPL.LineEdit.var"#22#23"{REPL.LineEdit.var"#109#162", String})(s::Any, p::Any)
│        @ REPL.LineEdit /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:1414
│     [15] prompt!(term::REPL.Terminals.TextTerminal, prompt::REPL.LineEdit.ModalInterface, s::REPL.LineEdit.MIState)
│        @ REPL.LineEdit /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2534
│     [16] run_interface(terminal::REPL.Terminals.TextTerminal, m::REPL.LineEdit.ModalInterface, s::REPL.LineEdit.MIState)
│        @ REPL.LineEdit /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2436
│     [17] run_frontend(repl::REPL.LineEditREPL, backend::REPL.REPLBackendRef)
│        @ REPL /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/REPL.jl:1126
│     [18] (::REPL.var"#44#49"{REPL.LineEditREPL, REPL.REPLBackendRef})()
│        @ REPL ./task.jl:411
│    in expression starting at none:1
└ @ REPL.LineEdit /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/REPL/src/LineEdit.jl:2536
julia>
julia>

(as this shows, even in the case where these is a valid name available e.g. @Meta.dump)

I think the appropriate behaviour here would be either (i) do nothing (treat @Meta.<tab> or @undefined.<tab> same as Nonexistant.<tab>), or possibly (ii) show the macro names that are valid e.g. @Meta.<tab> would show

julia> @Meta. # <tab>
dump        lower

But really i'd be happy with the first option (i) do nothing.

[simeonschaub]

Duplicate of #27184 which was fixed by #40621. Should be backported to 1.6 though.

[nickrobinson251]

that's the best!

i guess i should have checked using Nightly 😊

Thanks!