investigate tab completion for alias commands about myaliases HOT 2 CLOSED

An understanding of bash tab completions continues to elude me. There are three different systems I've encountered that all seem to do things differently: knuth, my phone, and my laptop.
A little bit of a breakthrough came when I played around with cds tab completion a while back. I'll document a few things I learned for posterity. Hopefully they can shed some light on how normal alias gets its completions too.

• Bash completions are not an inherent feature of bash necessarily. I think they need to get enabled by an external script.
• Bash completions get enabled every time the terminal is started. The following code needs to appear in your .bashrc in order for this to happen. In order for tab completions from our repo to work appropriately, our code needs to be sourced after this code is run.

# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if ! shopt -oq posix; then
  if [ -f /usr/share/bash-completion/bash_completion ]; then
    . /usr/share/bash-completion/bash_completion
  elif [ -f /etc/bash_completion ]; then
    . /etc/bash_completion
  fi
fi

• knuth does not have the above code. Neither does it have a bash_completion enabler script. Yet it seems to have some form of tab completion, albeit a really bad one. You can enable better bash completions on knuth by copying the script and adapting the code above to the appropriate places.
• Most computers also have a folder /etc/bash_completion.d/ where it seems like bash completion scripts for some individual commands (like git, for example) are stored. I have yet to understand what this does and why it exists.
• I still don't know where tab completions for normal cd are defined. @GiselleSerate, you might run into the same problem with normal alias since they are both bash built-in commands (I think?)

from myaliases.

Okay, tab completion was a little enthusiastic. Alias doesn't do any tab completing. (I don't know where it would . . .) So we're going to call this a case of Tab Completion Isn't Duct Tape and close this issue.

from myaliases.