Re: [PATCH v2] parallel-checkout: avoid dash local bug in tests

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 6, 2021, 01:28 UTC
Message-ID: <xmqqa6o3233q.fsf@gitster.g>
In-Reply-To: <5ed77a50-3b34-4f3d-8348-a11d3930872b@web.de>

René Scharfe <l.s.r@web.de> writes:

Show 17 quoted lines

> Am 05.06.21 um 21:56 schrieb Ævar Arnfjörð Bjarmason:
>>
>> On Sat, Jun 05 2021, René Scharfe wrote:
>>
>>> -	local workers=$(grep "child_start\[..*\] git checkout--worker" "$trace_file" | wc -l) &&
>>> -	test $workers -eq $expected_workers &&
>>> +	test $(grep -c "child_start\[..*\] git checkout--worker" "$trace_file") -eq $expected_workers &&
>>>  	rm "$trace_file"
>>>  } 8>&2 2>&4
>>
>> I'd find this thing much clearer if the v2 just narrowly focused on
>> avoiding the "local", and thus demonstrated the non-portable shell
>> issue,
>
> I was not aiming for a minimal fix and I don't think the patch above is
> too complex, but you're right that at this point in the release cycle a
> duct-tape-style patch would be better.

Sorry for being late to the party but I tend to disagree. "grep -c" is used elsewhere in the tests, we know it is safe.

IOW, the above change is quite straight-forward. It is much more obvious and close to "duct-tape-style" fix, than some altermatives like enclosing the whole command substitution in a pair of double-quotes and rely on $workers always getting used without double-quotes around it. To me, that looks more subtle and brittle.

Show 17 quoted lines

>> and perhaps with something like:
>>
>> 	diff --git a/t/check-non-portable-shell.pl b/t/check-non-portable-shell.pl
>> 	index fd3303552be..aad6f3e2bf1 100755
>> 	--- a/t/check-non-portable-shell.pl
>> 	+++ b/t/check-non-portable-shell.pl
>> 	@@ -48,6 +48,7 @@ sub err {
>> 	 	/\bexport\s+[A-Za-z0-9_]*=/ and err '"export FOO=bar" is not portable (use FOO=bar && export FOO)';
>> 	 	/^\s*([A-Z0-9_]+=(\w*|(["']).*?\3)\s+)+(\w+)/ and exists($func{$4}) and
>> 	 		err '"FOO=bar shell_func" assignment extends beyond "shell_func"';
>> 	+	/\blocal\b \S+=\$\(.*?\|\s*\bwc -l\)/ and err 'whitespace handling in local=$(... | wc -l) differs in some dash versions';
>
> Any command can output whitespace, it's not limited to wc -l.  So a
> better rule might be to always quote command substitutions in local
> variable declarations (local foo="$(...)").  Or to disallow assignments
> with local altogether, like we already do for export, but that might be
> a bit much.

I actually do not mind "no assignments with local decl" that much. I agree that is outside the scope of this particular fix.