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Re: Making substitute* throw an error if substition failed?
From: |
Ludovic Courtès |
Subject: |
Re: Making substitute* throw an error if substition failed? |
Date: |
Mon, 17 Oct 2016 10:50:36 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) |
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?
> This might be helpful for the more complex packages with many
> substitutions. If we make it return a value (#f for error) it would
> also make our build phases a little prettier, I think. (Now we
> forcefully return #t in any case and that seems wrong.)
I like this idea. Like others wrote, it could return #t if one or more
substitutions were made, and #f otherwise.
I think it’s better than throwing an error, because there are cases
where it doesn’t matter whether a substitution was made or not (e.g.,
when replacing strings en masse on a set of files.)
WDYT?
Thanks,
Ludo’.