[bug#50289] [PATCH] import: go: Fix import when import path redirects.

[Sarah Morgensen <iskarian@mgsn.dev>]

* guix/import/go.scm (fetch-module-meta-data): If no meta entries
have a matching import prefix, return the first entry instead of #f.
---
X-Debbugs-CC: Attila Lendvai <attila@lendvai.name>

Hello Guix,

As reported by Attila on IRC, the Go importer currently chokes when the
import path URL redirects, for example with "github.com/prometheus/tsdb".

This is due to my modification to 'fetch-module-meta-data' to handle multiple
package's meta tags on one page [0].  It selects the meta based on whether its
import prefix matches the URL we requested.  This breaks when the URL
redirects but the import path is not changed (I did not realize that this
was valid... go figure).  This patch fixes that by falling back to the first
meta if none match.

[0] https://issues.guix.gnu.org/49591

--
Sarah

 guix/import/go.scm | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/guix/import/go.scm b/guix/import/go.scm
index 617a0d0e23..57a135b9a9 100644
--- a/guix/import/go.scm
+++ b/guix/import/go.scm
@@ -483,9 +483,12 @@ (define (fetch-module-meta-data module-path)
     (match (select (html->sxml meta-data #:strict? #t))
       (() #f)                           ;nothing selected
       ((('content content-text) ..1)
-       (find (lambda (meta)
-               (string-prefix? (module-meta-import-prefix meta) module-path))
-             (map go-import->module-meta content-text))))))
+       (or
+        (find (lambda (meta)
+                (string-prefix? (module-meta-import-prefix meta) module-path))
+              (map go-import->module-meta content-text))
+        ;; Fallback to the first meta if no import prefixes match.
+        (go-import->module-meta (first content-text)))))))
 
 (define (module-meta-data-repo-url meta-data goproxy)
   "Return the URL where the fetcher which will be used can download the

base-commit: 994d8ce394e88b55985241b7b14f6a8459bcf9e8
-- 
2.31.1