From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Making substitute* throw an error if substition failed?
Date: Tue, 18 Oct 2016 14:41:51 +0200
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	<20161017210836.GF14171@macbook42.flashner.co.il>
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	Flashner's message of "Tue, 18 Oct 2016 00:08:36 +0300")
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To: Efraim Flashner <efraim@flashner.co.il>
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Efraim Flashner <efraim@flashner.co.il> skribis:

> On Mon, Oct 17, 2016 at 10:50:36AM +0200, Ludovic Court=C3=A8s wrote:
>> Hi,
>>=20
>> Ricardo Wurmus <rekado@elephly.net> skribis:
>>=20
>> > it happened a couple of times already that a =E2=80=9Csubstitute*=E2=
=80=9D expression
>> > silently failed and I only found out about it when investigating the
>> > remains of a failing build (=E2=80=9Cguix build -K=E2=80=9D).  This ca=
n easily happen
>> > when a package is updated and substitutions =E2=80=9Canchors=E2=80=9D =
no longer exist in
>> > the updated source code.
>> >
>> > Would it be desirable to change =E2=80=9Csubstitute*=E2=80=9D (or repl=
ace it) such that
>> > it throws an error or returns a value if substitution failed?
>>=20
>> =E2=80=9CFailed=E2=80=9D as in =E2=80=9Cthere were no pattern matches=E2=
=80=9D, right?
>>=20
>
> Or as in "your regex was bad, try again"

That already happens.

Ludo=E2=80=99.