From: Johannes Sixt <j6t@kdbg.org>
Date: Wed, 27 Jun 2018 06:27:34 GMT
Subject: Re: [PATCH 29/29] t/test-lib: teach --chain-lint to detect broken &&-chains in subshells
Message-ID: <67110b53-690c-abd4-9988-33278ee8c413@kdbg.org>
In-Reply-To: <CABPp-BHgPgkgQj7i3rZtdbinVZvqH35uGraUK9doL-E8Y5QuSQ@mail.gmail.com>

Am 27.06.2018 um 04:15 schrieb Elijah Newren:
> On Tue, Jun 26, 2018 at 2:01 PM, Jeff King <peff@peff.net> wrote:
>> On Tue, Jun 26, 2018 at 04:46:18PM -0400, Eric Sunshine wrote:
> 
>>> Some of these dangers can be de-thoothed during the linting phase by
>>> defining do-nothing shell functions:
>>>
>>>      cp () { :; }
>>>      mv () { :; }
>>>      ln () { :; }
>>>
>>> That, at least, makes the scariest case ("rm") much less so.
>>
>> Now that's an interesting idea. We can't catch every dangerous action
>> (notably ">" would be hard to override), but it should be pretty cheap
>> to cover some obvious ones.
>>
>> -Peff
> 
> Crazy idea: maybe we could defang it a little more thoroughly with
> something like the following (apologies in advance if gmail whitespace
> damages this):
> 
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index 28315706be..7fda08a90a 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -675,7 +675,7 @@ test_run_ () {
>                  trace=
>                  # 117 is magic because it is unlikely to match the exit
>                  # code of other programs
> -               if test "OK-117" != "$(test_eval_ "(exit 117) &&
> $1${LF}${LF}echo OK-\$?" 3>&1)"
> +               if test "OK-117" != "$(test_eval_ "cd() { return 0; }
> && PATH=/dev/null && export PATH && (exit 117) && $1${LF}${LF}echo
> OK-\$?" 3>&1)"
>                  then
>                          error "bug in the test script: broken &&-chain
> or run-away HERE-DOC: $1"
>                  fi

I'd define all these functions as { return 1; } because we want to stop 
any && chain as early as possible (and with an exit code that is not the 
sentinel value).

-- Hannes