Autocomplete on command-line search pattern returns strange symbols of <09> and ^I

Question

Using Neovim v0.4.3 on a just recently upgraded Linux Mint 19.3.

Problem Description:

After the upgrade, when typing / followed by first characters of any word below the cursor, in the buffer, and pressing the <Tab>, Neovim return on the command-line a strange <09> symbol.

Expected Behavior:

Before the upgrade, when typing / followed by first characters of any word below the cursor, in the buffer, and pressing the <Tab>, Neovim would gracefully autocomplete the search on the command-line.

Steps Taken to Remedy

1. Applied same init.vim configuration as before upgrade (problem persisted)
2. Searched for solution or any hint on google.
3. Scanned throw Neovim 'cmdline-completion' manual and tested a number of combinations on 'wildchar', 'wildmenu' and 'wildmode'.
4. Created a minimal init.vim and tested above behavior on stripped '.vimrc' with no plugins and minimal configuration:

     set nocompatible
     filetype plugin indent on
     syntax on
     set hidden

Tested above behavior after opening Nvim: $ nvim -u $HOME/.config/nvim/mini.vim

Now, when typing / followed by first characters of any word below the cursor, in the buffer, and pressing the <Tab>, Neovim returns on command-line a strange ^I symbol.

Kindly, assist in solving this problem. Your solution, idea, hint, or guidance is greatly appreciated.

Answer 1

The hex code of <tab> is 0x09 and is equivalent to <C-i> (displayed as ^I).

To insert the word under the cursor in the command line, you need <C-r><C-w>.

So you are missing a mapping from <tab> to <C-r><C-w>:

cnoremap <tab> <C-r><C-w>