Suggest modern [[ instead of [ or test in Bash

[l0b0]

For new checks and feature suggestions

• https://www.shellcheck.net/ (i.e. the latest commit) currently gives no useful warnings about this
• I searched through https://github.com/koalaman/shellcheck/issues and didn't find anything related

Update: https://www.shellcheck.net/wiki/SC2292 is similar (Does it apply to test as well? I'd assume so…), but is not enabled at https://www.shellcheck.net/. Do we need an "all rules enabled" version of that page linked from the issue template?

Here's a snippet or screenshot that shows the problem:

#!/usr/bin/env bash
[ -n "$foo" ]
test -n "$foo"

Here's what shellcheck currently says:

No issues detected!

Here's what I wanted or expected to see:

Use "[[" instead of "["
Use "[[" instead of "test"

Rationale: [[ is generally safer and saner than [/test. See for example [[ Is a Builtin, But [[ Is Part of the Language and What is the difference between test, [ and [[?.

[brother]

As mentioned in the linked wiki page (SC2292) this is an optional check and must be activated explicit, shellcheck.net is operating in a "default mode".
Suggestions for changes to shellcheck.net is better discussed at that issue board - for instance adding a checkbox or something for "enable all optinal rules" or something.

shellcheck -o require-double-brackets myscript.sh

name:    require-double-brackets
desc:    Require [[ and warn about [ in Bash/Ksh
example: [ -e /etc/issue ]
fix:     [[ -e /etc/issue ]]