bug#49827: Error message for missing synopsis in opam importer

[Sarah Morgensen <iskarian@mgsn.dev>]

Hi,

Thanks for the report. I'm CC'ing Simon since they have been working on
improved error handling/reporting for the importers.

Alice BRENON <alice.brenon@ens-lyon.fr> writes:

> Hello,
>
> I triggered a confusing behaviour from the opam importer trying to
> import package iter 1.2.1 today on a Guix System install.
>
> The package iter is missing a "synopsis" field as can be seen on
> https://opam.ocaml.org/packages/iter/ , which when I tried
>
> guix import opam iter
>
> yielded the following backtrace:
>
> Backtrace:
>            8 (primitive-load "/home/alice/.config/guix/current/bin/g…")
> In guix/ui.scm:
>    2185:7  7 (run-guix . _)
>   2148:10  6 (run-guix-command _ . _)
> In guix/scripts/import.scm:
>    120:11  5 (guix-import . _)
> In guix/scripts/import/opam.scm:
>    104:23  4 (guix-import-opam . _)
> In guix/utils.scm:
>     752:8  3 (call-with-temporary-output-file _)
> In guix/import/opam.scm:
>    337:34  2 (_ _ _)
> In srfi/srfi-1.scm:
>    460:18  1 (fold #<procedure 7f3baca56fe0 at guix/import/opam.scm…> …)
> In guix/import/opam.scm:
>    193:15  0 (_ _ _)
>
> guix/import/opam.scm:193:15: Throw to key `match-error' with args
> `("match" "no matching pattern" string-pat)'.
>
>
> the final error is raised l.193 of guix/import/opam.scm because
> metadata-ref supports various types for a metadata field, but not the
> lack of it. As discussed with Maxime Devos on the IRC channel, it would
> be helpful to either allow the import of a package with a missing field
> (possibly filling it in the output scheme code for the imported package
> with some bad value requiring the user to fill it and causing any build
> to crash until replaced properly) or at least to handle that missing
> field with a more explicit error message than the above backtrace
> (something like "Can't import that package because it's missing such or
> such field").

IMO, a warning should be emitted, but the package should be buildable if
at all possible; it's the submitter's responsibility to vet imported
packages.

Simon, how's that error handling rework coming? ;)

>
> Thanks,
>
> Alice BRENON

--
Sarah