complete-alias

automagical shell alias completion;

works with all common aliases, even self-aliases;
one completion function, for all aliases;
alias completion as easy as type-and-tab;

install

install dependency bash-completion;
- linux:
  
  install bash-completion using system package manager:
```
dnf install bash-completion     ##  fedora
apt install bash-completion     ##  debian
```
  for other linux distros, see faq;
- macos (experimental):
  
  install bash-completion homebrew formulae version 2:
```
brew install bash-completion@2
```
- windows (experimental):
  
  see faq;
source complete_alias in ~/.bash_completion:
```
. {complete_alias}
```
where {complete_alias} is the path of complete_alias;

usage

edit aliases to complete in complete_alias:

for example, to complete aliases foo, bar and baz:

complete -F _complete_alias foo
complete -F _complete_alias bar
complete -F _complete_alias baz

to complete an alias, type it and press <tab>;

example

to complete alias sctl aliased to systemctl:

$ alias sctl='systemctl'
$ cp complete_alias ~/.complete_alias
$ echo ". ~/.complete_alias" >> ~/.bash_completion
$ echo "complete -F _complete_alias sctl" >> ~/.complete_alias
$ sctl <tab>
add-requires
add-wants
cancel
cat
condreload
...

config

to config complete-alias, set these envars before sourcing the main script:

COMPAL_AUTO_UNMASK

this is a bool; default is 0; when set to 1, enables auto unmask; when set to 0, uses manual unmask;

auto unmask automatically manages non-alias command completions, but incurs a small overhead on source; manual unmask is the traditional way of setting non-alias command completions, which is static and faster but requires user intervention if the preset is not satisfying;

compat

support for gnu bash(>=4.4) on linux is aimed;
support for older versions of bash is uncertain;
support for other shells is possible but unlikely;
support for other operating systems is experimental;

faq

how to install it on windows?

support for windows is limited to msys2 and git for windows:
- msys2:
  
  msys2 features pacman so you can install like linux:
```
pacman -S bash-completion
cat complete_alias >> ~/.bash_completion
```
- git for windows:
  
  tldr: steal bash_completion and source it before complete_alias;
  
  git for windows provides git bash, which is a minimal environment based on msys2; for what matters here, git bash does not have package manager; so the above install procedure does not apply;
  
  the idea is, you must somehow get bash-completion and load it before complete-alias in a shell environment; for example, you can download bash-completion package from a msys2 mirror; however, the easiest solution i found to make things work is to simply download the main script bash_completion from its git repo; this does not give you its entirety, but is good enough to work;
  
  now you have 2 files: bash_completion and complete_alias; you need to source them in this order in ~/.bashrc:
```
. ~/.bash_completion.sh
. ~/.complete_alias.sh
```
  attention: here we renamed the files; we cannot use ~/.bash_completion because this is the very filename sourced by the very script; using this filename will cause an infinite loop;
  
  now install is complete; add your own aliases in ~/.complete_alias.sh;

how to install bash-completion on other linux distros?

these commands are sourced from wikis and users:

pacman -S bash-completion               ##  arch
yum install bash-completion             ##  centos
emerge --ask app-shells/bash-completion ##  gentoo
zypper install bash-completion          ##  suse
apt install bash-completion             ##  ubuntu

these commands are not tested; open a ticket if you find them not working;

how to complete all my aliases?

run this one-liner after all aliases have been defined:
```
complete -F _complete_alias "${!BASH_ALIASES[@]}"
```
it works like this:
```
complete -F _complete_alias foo
complete -F _complete_alias bar
complete -F _complete_alias baz
...
```
note that if you simply put this one-liner in complete_alias code, things may not work, depending on the order of file sourcing, which in turn varies across user configurations; the correct way to use this one-liner is to put it in the same file where aliases are defined; for example, if your aliases are defined in ~/.bashrc, then that file should look like this:
```
alias foo='...'
alias bar='...'
alias baz='...'
...
complete -F _complete_alias "${!BASH_ALIASES[@]}"
```
what are special characters in alias body?

these characters have special meanings and may cause errors when used in alias body (this is not a complete list):
- newline (\n):
  
  we do not allow alias body to contain the newline character; this limits the cases to consider and makes smaller, faster code; we treat a newline as a word breaker in the outmost scope, but you better not rely on this;
- backquote (`):
  
  avoid the old-style backquote form `command` of command substitution as much as possible; instead, use the $(command) form; the backquote form is more tricky and less legible when nested in quotes or another command substitution; we do not intend to fully support backquotes;
- backslash (\):
  
  avoid backslashes unless you absolutely have to use them; they are mostly used to escape a character; we have double quotes that can do the same; the bash manual is not complete on where a backslash is special and where it is literal; and we may make mistakes on its interpretation;
- colon (:):
  
  a colon seems innocent but is special to word completion code: it is one of the characters that breaks words for the completer; you can read more about it at this link; however, we do not guarantee the same treatment of colons here as there; we treat a colon as a word breaker in the outmost scope and a literal otherwise; if you always want it to be a literal, just quote it;
why is sudo completion not working correctly?

there is a known case with sudo that can go wrong; for example:
```
$ unalias sudo
$ complete -r sudo
$ alias ls='ping'
$ complete -F _complete_alias ls
$ sudo ls <tab>
{ip}
{ip}
{ip}
...
```
here we are expecting a list of files, but the completion reply is a list of ip addrs; the reason is, the completion function for sudo is almost always _sudo, which is provided by bash-completion; this function strips sudo then meta-completes the remaining command line; in our case, this is ls to be completed by _complete_alias; but there is no way for _complete_alias to see the original command line, and so it cannot tell ls from sudo ls; as a result, ls and sudo ls are always completed the same even when they should not; unfortunately, there is nothing _complete_alias can do here;

the easiest solution is to make sudo a self-alias:
```
$ alias sudo='sudo'
$ complete -F _complete_alias sudo
$ alias ls='ping'
$ complete -F _complete_alias ls
$ sudo ls <tab>
{file}
{file}
{file}
...
```
this gives _complete_alias a chance to see the original command line, then decide what is the right thing to do; you may add a trailing space to sudo alias body if you like it that way, and things still work correctly (listing ip addrs is correct in this case):
```
$ alias sudo='sudo '
$ complete -F _complete_alias sudo
$ alias ls='ping'
$ complete -F _complete_alias ls
$ sudo ls <tab>
{ip}
{ip}
{ip}
...
```

license

The source code is licensed under the GNU General Public License v3.0.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

seryte/complete-alias