Supertab doesn't work in command-line window about supertab HOT 4 CLOSED

Hmm, seems to work fine for me. Do you have paste (:set paste?) enabled in your command window?

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from supertab.

I figured it out somewhat. Fist thing is that we may use different compilations of vim:

"When Vim was compiled without the +cmdline_compl feature only file names,
directories and help items can be completed. The number of help item matches
is limited (currently to 300) to avoid a long delay when there are very many
matches."

I finally noticed I have this behaviour for :imap <Tab>
In a normal window:

i  <Tab>         <Plug>SuperTabForward

In the command line window:

i  <Tab>        @<C-X><C-V>
i  <Tab>         <Plug>SuperTabForward

Then I found the exactly same, unresolved problem that I face:
https://groups.google.com/forum/#!topic/vim_use/EX93BOy4XZM/discussion

QUOTE
I am trying to disable the default mapping for the tab key to @A in command window. according to :h command-line-window, adding the following two lines in .vimrc should do the job but it doesn't to my test.
au CmdwinEnter [:>] iunmap
au CmdwinEnter [:>] nunmap
below is the min repo vimrc I observed this behavior.
set nocompatible
au CmdwinEnter [:>] iunmap
au CmdwinEnter [:>] nunmap

once in command window (either by : then ctrl-f, or q: in normal mode), :map still shows "n @A", which conflicts/overwrites my other mapping for the tab key.

set wildchar= seems to avoid the default mapping, but I do want to use tab for auto-completion in vim. I also tried tightening the scope of non-tab wildchar with
au CmdwinEnter [:>] set wildchar=
au CmdwinLeave [:>] set wildchar=
but this doesn't work either.

meanwhile, with vim help recommended setting, I always got this error on entering command window:
Error detected while processing CmdwinEnter Auto commands for "[:>]":
E31: No such mapping
Press ENTER or type command to continue

it feels like by the time CmdwinEnter is triggered, the default tab mapping is not injected yet, and somehow it comes in at a later phase, but still before my "set wildchar=" takes effect, which is really confusing.

how can I disable them permanently? I am on vim 8.0.1420. thanks.
END OF QUOTE

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As inspect it further, I can see that <S-Tab> is not affected by this, as I understand, broken vim behaviour. So this solves the issue for me: I will go with shift tab always.

from supertab.