How do I make Tab trigger wildmenu completion inside a custom mapping?

Explanation

By default, pressing <Tab> in a : mapping inserts a literal tab character rather than triggering wildmenu completion. Setting 'wildcharm' to the same key as 'wildchar' (usually <Tab>) tells Vim that that key should activate completion even when typed inside a mapping.

This unlocks a common power-user pattern: a mapping that pre-fills a command and then lets you interactively complete the rest with Tab.

How it works

• 'wildchar' is the key that triggers completion when typing manually at the command line (default: <Tab>)
• 'wildcharm' is the key that triggers completion when the command line is opened from a mapping
• Without wildcharm, <Tab> in a mapping is treated as a literal character

Example

Add to your vimrc:

set wildcharm=<Tab>
nnoremap ,e :e <Tab>

Now pressing ,e opens the :e prompt and immediately displays the wildmenu file browser. You can continue typing or pressing Tab to navigate directory contents interactively.

Another practical mapping:

nnoremap ,b :b <Tab>

This lets you pick from the buffer list with completion rather than memorising buffer numbers.

Tips

• wildcharm must be set to the same character as wildchar for intuitive behaviour; any other character works too but is unusual
• Works best with set wildmenu and set wildmode=longest:list,full
• Combine with set wildignore to suppress noisy completions (e.g. *.o,*.pyc)
• This setting has no effect at the interactive command line — only inside mappings that programmatically open it