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

On Sat, Jun 5, 2021 at 5:03 PM Ævar Arnfjörð Bjarmason [off-list ref] wrote:

On Sat, Jun 05 2021, René Scharfe wrote:

quoted

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 [off-list ref]
Signed-off-by: René Scharfe <redacted>
---
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.