bug#52362: [PATCH v3] guix: import: go: Use correct tag for go module in subdirectory.

[Stephen Paul Weber]

https://go.dev/ref/mod says a module in a subdirectory has a tag prefixed with
the subdirectory.

* guix/import/go.scm (version+subdirectory->tag-prefix): New variable.
(vcs->origin): New argument module-path-subdirectory.
---
 guix/import/go.scm | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/guix/import/go.scm b/guix/import/go.scm
index d00c13475a..f2ea9dbbae 100644
--- a/guix/import/go.scm
+++ b/guix/import/go.scm
@@ -521,28 +521,37 @@ tag."
                                           `(tag-or-commit . ,reference)))))
     (file-hash* checkout #:algorithm algorithm #:recursive? #true)))
 
-(define (vcs->origin vcs-type vcs-repo-url version)
+(define (version+subdirectory->tag-prefix subdirectory)
+  (if (string=? subdirectory "")
+      ""
+      (string-append (substring subdirectory 1) "/")))
+
+(define (vcs->origin vcs-type vcs-repo-url module-path-subdirectory version)
   "Generate the `origin' block of a package depending on what type of source
 control system is being used."
   (case vcs-type
     ((git)
-     (let ((plain-version? (string=? version (go-version->git-ref version)))
-           (v-prefixed?    (string-prefix? "v" version)))
+     (let* ((plain-version? (string=? version (go-version->git-ref version)))
+            (v-prefixed?    (string-prefix? "v" version))
+            (tag-prefix     (version+subdirectory->tag-prefix
+                             module-path-subdirectory))
+            (git-commit     (if plain-version?
+                                (string-append tag-prefix version)
+                                (go-version->git-ref version))))
        `(origin
           (method git-fetch)
           (uri (git-reference
                 (url ,vcs-repo-url)
-                ;; This is done because the version field of the package,
-                ;; which the generated quoted expression refers to, has been
-                ;; stripped of any 'v' prefixed.
                 (commit ,(if (and plain-version? v-prefixed?)
-                             '(string-append "v" version)
+                             (if (string=? module-path-subdirectory "")
+                                 '(string-append "v" version)
+                                 `(string-append ,tag-prefix "v" version))
                              '(go-version->git-ref version)))))
           (file-name (git-file-name name version))
           (sha256
            (base32
             ,(bytevector->nix-base32-string
-              (git-checkout-hash vcs-repo-url (go-version->git-ref version)
+              (git-checkout-hash vcs-repo-url git-commit
                                  (hash-algorithm sha256))))))))
     ((hg)
      `(origin
@@ -618,12 +627,17 @@ When VERSION is unspecified, the latest version available 
is used."
                            dependencies+versions
                            (map car dependencies+versions)))
          (module-path-sans-suffix
-          (match:prefix (string-match "([\\./]v[0-9]+)?$" module-path)))
+           (if (string-prefix? "gopkg.in" module-path)
+               module-path
+               (match:prefix (string-match "([\\./]v[0-9]+)?$" module-path))))
          (guix-name (go-module->guix-package-name module-path))
-         (root-module-path (module-path->repository-root module-path))
+         (root-module-path (module-path->repository-root 
module-path-sans-suffix))
          ;; The VCS type and URL are not included in goproxy information. For
          ;; this we need to fetch it from the official module page.
          (meta-data (fetch-module-meta-data root-module-path))
+         (module-path-subdirectory
+           (substring module-path-sans-suffix
+             (string-length (module-meta-import-prefix meta-data))))
          (vcs-type (module-meta-vcs meta-data))
          (vcs-repo-url (module-meta-data-repo-url meta-data goproxy))
          (synopsis (go-package-synopsis module-path))
@@ -634,7 +648,7 @@ When VERSION is unspecified, the latest version available 
is used."
         (name ,guix-name)
         (version ,(strip-v-prefix version*))
         (source
-         ,(vcs->origin vcs-type vcs-repo-url version*))
+         ,(vcs->origin vcs-type vcs-repo-url module-path-subdirectory 
version*))
         (build-system go-build-system)
         (arguments
          '(#:import-path ,module-path
-- 
2.30.2