Remapping tab key to autocomplete in commandline mode in Vim

Question

I am using Vim 7.4 and I wish to map the tab key so I can use new combinations to autocomplete arguments in command mode from the current directory

Contents of current directory:

Funwithstrings.cs Funwithstrings.exe Funwithstrings.cs~

Using vim in this directory : I am using following mapping in vim

:map! as <tab>

Now upon trying this in command mode in the manner

:e Fuas.  

I get

:e Fu^I

I.e., ^I two characters instead of special character <tab> instead of one of the filenames-- expected results with tab key. In a different computer I get :e Fu<Tab> - 5 characters.

What am I doing wrong? I am using screen 256 terminal.

Answer 1

By default with nocompatible, vim sets wildchar to <tab> which enables you to tab complete "out of the box." However, this does not extend to <tab>s produced by mappings.

For example, if we cnoremap as <tab>, pressing as, vim will type literal tabs, which in this case render as ^I.

The solution is to use wildcharm, which is "recognized when used inside a macro" (see :help wildcharm):

set wildcharm=<tab>.

An alternative to making a mapping to <tab> is to just set wildchar or wildcharm to the key you want. This works only for single characters.

Answer 2

As Mass mentioned above, wildchar can contain only one character. It’s restricted by vim design. But it’s actually restricted to use a non-ascii symbol for wildchar either. In most cases, it doesn’t matter because people usually use vim for programming only (that means using English letters only) and don’t change their keyboard layouts for smart tricks. But I do!

So, the wildchar option can be left as is, i.e. <Tab>. Then, to avoid complex constructions in <C-r>= create a little function that emulates the keystrokes. At last, map the key sequence you want to use in Command mode to that function.

For example, assume we want to use the as sequence for the autocompletion. In such a case, somewhere in .vimrc:

function! s:wildchar()
    call feedkeys("\<Tab>", 'nt')
    return ''
endfunction

cnoremap <silent> as <C-r>=<SID>wildchar()<CR>

Voila!