Re: [PATCH 2/2] test-lib: teach test_seq the -f option

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Jun 24, 2025, 06:22 UTC
Message-ID: <CAPig+cQNWVd7M5pe0te9os3NRrjfBSSaUZjUXKX8RUdTk50SFw@mail.gmail.com>
In-Reply-To: <20250623105625.GB654412@coredump.intra.peff.net>

On Mon, Jun 23, 2025 at 6:56 AM Jeff King <peff@peff.net> wrote:

Show 23 quoted lines

> The "seq" tool has a "-f" option to produce printf-style formatted
> lines. Let's teach our test_seq helper the same trick. This lets us get
> rid of some shell loops in test snippets (which are particularly verbose
> in our test suite because we have to "|| return 1" to keep the &&-chain
> going).
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> diff --git a/t/t0612-reftable-jgit-compatibility.sh b/t/t0612-reftable-jgit-compatibility.sh
> @@ -112,14 +112,11 @@ test_expect_success 'JGit can read multi-level index' '
> -               awk "
> -                   BEGIN {
> -                       print \"start\";
> -                       for (i = 0; i < 10000; i++)
> -                           printf \"create refs/heads/branch-%d HEAD\n\", i;
> -                       print \"commit\";
> -                   }
> -               " >input &&
> +               {
> +                       echo start &&
> +                       test_seq -f "create refs/heads/branch-%d HEAD" 10000 &&
> +                       echo commit
> +               } >input &&

I had suggested[1] an effectively equivalent change to Patrick for a couple tests in the nearby t0610, but he rejected[2] the idea due to the pure-shell version being significantly slower than the `awk` version.

Pondering his response today, I wondered if it would make sense to replace our pure-shell `test_seq` with an implementation via `awk`, however, if most of our sequence vend only a small set of numbers, then the startup cost of `awk` would probably swamp any savings, especially on Windows where process startup is extremely slow. Taking that into account, I further wondered if we could see an overall win by taking a hybrid approach in which we employ the pure-shell version if vending a small set of numbers, but fall over to an `awk` version if vending a lot of numbers, especially as in the test above or the tests in t0610. Anyhow, food for thought, or not, if you're not hungry for thought food.

[1]: https://lore.kernel.org/git/CAPig+cSC3zdur1fCsa7RMNZDcgUK4pUGKb22tpgdANxR6OxNMA@mail.gmail.com/ [2]: https://lore.kernel.org/git/Z-FUNgmY9hTsnzds@pks.im/