This command works without errors:

:echo v:oldfiles->copy()->filter('v:val =~# "txt$"')

(see :h method, :h v:oldfiles, :h v:val and :h =~#)

I want to create a custom command / function combination that wraps the :echo and still accepts the v:oldfiles->copy()->filter('v:val =~# "txt$"') argument like in the :echo did.

I have this:

command! -bar -complete=expression -nargs=1 Foo call FooFunc(<args>)

function! FooFunc(x) 
    echo a:x

However, invoking :Foo v:oldfiles->copy()->filter('v:val =~# "txt$"') results in the error:

E115: Missing quote: 'v:val =~#

How can I make it work like the :echo?

  1. For this particular task it's much much easier to do simply

    :filter /txt$/ oldfiles
  2. The error is due to -bar argument: the quote is parsed like a comment sign, and so the rest of the command is lost (see :h :command-bar, :h :quote).

Either always escape all quotes (and bars) with backslashes, or remove -bar argument from the command definition.

  • Wouldnt it also need to be execute 'echo' a:x? – D. Ben Knoble Sep 19 '20 at 13:01
  • 2
    @D.BenKnoble Here we have FooFunc(<args>), i.e. the argument is non-quoted. Hence an expression gets evaluated upon function call and no execute is needed. Of course, that could result in some other errors, such as :Foo 1,2 --> Too many parameters, etc.etc. – Matt Sep 19 '20 at 13:09
  • 1
    Huh! That's pretty interesting! But -bar is about recognizing | as a command separator, what does " as a comment character has to do with it? Why are these two connected? (I don't doubt that this is correct and indeed how it works, just wondering why it's that way...) – filbranden Sep 19 '20 at 13:23
  • For instance, :echo "a" | echo "b" works just fine... So it's akin to a user-defined command that has -bar, but it doesn't take " as comments... Yes, user-defined commands are somewhat different from built-ins, but still wondering why this is the way it is. – filbranden Sep 19 '20 at 13:26
  • 2
    @filbranden That's how it works: in a user command one can only switch on/off both simultaneously using "-bar". Not a case for internal commands such as :echo. So, yes, this is really frustrating :-(( – Matt Sep 19 '20 at 13:45

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