Re: Making substitute* throw an error if substition failed?

[Ludovic Courtès]

Efraim Flashner <address@hidden> skribis:

> On Mon, Oct 17, 2016 at 10:50:36AM +0200, Ludovic Courtès wrote:
>> Hi,
>> 
>> Ricardo Wurmus <address@hidden> skribis:
>> 
>> > it happened a couple of times already that a “substitute*” expression
>> > silently failed and I only found out about it when investigating the
>> > remains of a failing build (“guix build -K”).  This can easily happen
>> > when a package is updated and substitutions “anchors” no longer exist in
>> > the updated source code.
>> >
>> > Would it be desirable to change “substitute*” (or replace it) such that
>> > it throws an error or returns a value if substitution failed?
>> 
>> “Failed” as in “there were no pattern matches”, right?
>> 
>
> Or as in "your regex was bad, try again"

That already happens.

Ludo’.