```shell
$ set -u
$ foo=()
$ echo ${#foo}
bash: foo: unbound variable
echo ${#foo[*]}
0
```
The above shows that an empty array needs the suffix `[*]` when checking its length, or else it is considered unbound.
Fixes#1734
Tab characters that introduce completion descriptions weren't properly
being handled with bash v3. This change fixes that.
Signed-off-by: Marc Khouzam <marc.khouzam@gmail.com>
Not that it'd really matter that much performancewise given the level we
are at for this case, but this change makes the short circuit roughly
twice as fast on my box as it was for the 1000 rounds done in
marckhouzam/cobra-completion-testing.
Perhaps more importantly, this makes the code arguably slightly cleaner.
If the list of candidates has no descriptions, short circuit all the
description processing logic, basically just do a `compgen -W` for the
whole list and be done with it.
We could conceivably do some optimizations like this and more when
generating the completions with `--no-descriptions` in Go code, by
omitting some parts we know won't be needed, or doing some things
differently. But doing it this way in bash, the improvements are
available also to completions generated with descriptions enabled when
they are invoked for completion cases that produce no
descriptions. The result after this for descriptionless entries seems
fast enough so it seems there's no immediate need to look into doing
that.
Refactor to remove two loops over the entire list of candidates.
Format descriptions only for completions that are actually going to be
displayed, instead of for all candidates.
Format descriptions inline in completions array, removing need for a
command substitution/subshell and a printf escape per displayed
completion.
Using a command substitution, i.e. a subshell, with `printf` is
expensive for this purpose. For example `__*_format_comp_descriptions`
is run once for each completion candidate; the expense adds up and
shows when there are a lot of them.
* Bash completion v2
This v2 version of bash completion is based on Go completions.
It also supports descriptions like the other shells.
Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>
* Only consider matching completions for formatting
Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>
* Use bash compV2 for the default completion command
Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>
* Update comments that still referred to bash completion
Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>
