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

[Matheus Tavares Bernardino <matheus.bernardino@usp.br>]

On Sat, Jun 5, 2021 at 5:03 PM Ævar Arnfjörð Bjarmason <avarab@gmail.com> wrote:
>
>
> On Sat, Jun 05 2021, René Scharfe wrote:
>
> > The parallel checkout tests fail when run with /bin/dash on MacOS 11.4,
> > reporting the following error:
> >
> >    ./t2080-parallel-checkout-basics.sh: 33: local: 0: bad variable name
> >
> > That's because wc's output contains leading spaces and this version of
> > dash erroneously expands the variable declaration as "local workers= 0",
> > i.e. it tries to set the "workers" variable to the empty string and also
> > declare a variable named "0", which not a valid name.  This is a known
> > dash bug (https://bugs.launchpad.net/ubuntu/+source/dash/+bug/139097).
> >
> > Work around it by passing the command output directly to test instead of
> > storing it in a variable first.  While at it, let grep count the number
> > of lines instead of piping its output to wc, which is a bit shorter and
> > more efficient.
> >
> > Helped-by: Matheus Tavares Bernardino <matheus.bernardino@usp.br>
> > Signed-off-by: René Scharfe <l.s.r@web.de>
> > ---
> > Changes since v1:
> > - Explain the root cause.
> > - Get rid of the local variable "workers".
> > - Adjust title accordingly.
> > - Still use grep -c, though.
> > - Remove input redirection.
> >
> >  t/lib-parallel-checkout.sh | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/t/lib-parallel-checkout.sh b/t/lib-parallel-checkout.sh
> > index 21f5759732..66350d5207 100644
> > --- a/t/lib-parallel-checkout.sh
> > +++ b/t/lib-parallel-checkout.sh
> > @@ -27,8 +27,7 @@ test_checkout_workers () {
> >       rm -f "$trace_file" &&
> >       GIT_TRACE2="$(pwd)/$trace_file" "$@" 2>&8 &&
> >
> > -     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 don't have any strong preference, but if we are leaving the "grep |
wc -l" -> "grep -c" conversion to a followup patch, perhaps the
simplest change focusing on the dash issue would be to quote the
right-hand side of the "local" assignment:

-     local workers=$(grep "child_start\[..*\] git checkout--worker"
"$trace_file" | wc -l) &&
+     local workers="$(grep "child_start\[..*\] git checkout--worker"
"$trace_file" | wc -l)" &&

(René, could you confirm if this works to make the test pass on dash?)

Alternatively, we could use `test_line_count` as SZEDER Gábor
suggested in a parallel reply.