1 files changed, 34 insertions, 1 deletions
diff --git a/guix/build-system/go.scm b/guix/build-system/go.scm
index f8ebaefb27..0e2c1cd2ee 100644
--- a/guix/build-system/go.scm
+++ b/guix/build-system/go.scm
@@ -26,9 +26,12 @@
   #:use-module (guix build-system gnu)
   #:use-module (guix packages)
   #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
   #:export (%go-build-system-modules
             go-build
-            go-build-system))
+            go-build-system
+
+            go-version->git-ref))
 
 ;; Commentary:
 ;;
@@ -37,6 +40,36 @@
 ;;
 ;; Code:
 
+(define %go-version-rx
+  (make-regexp (string-append
+                "(v?[0-9]\\.[0-9]\\.[0-9])" ;"v" prefix can be omitted in version prefix
+                "(-|-pre\\.0\\.|-0\\.)"     ;separator
+                "([0-9]{14})-"              ;timestamp
+                "([0-9A-Fa-f]{12})")))      ;commit hash
+
+(define (go-version->git-ref version)
+  "Parse VERSION, a \"pseudo-version\" as defined at
+<https://golang.org/ref/mod#pseudo-versions>, and extract the commit hash from
+it, defaulting to full VERSION if a pseudo-version pattern is not recognized."
+  ;; A module version like v1.2.3 is introduced by tagging a revision in the
+  ;; underlying source repository.  Untagged revisions can be referred to
+  ;; using a "pseudo-version" like v0.0.0-yyyymmddhhmmss-abcdefabcdef, where
+  ;; the time is the commit time in UTC and the final suffix is the prefix of
+  ;; the commit hash (see: https://golang.org/ref/mod#pseudo-versions).
+  (let* ((version
+          ;; If a source code repository has a v2.0.0 or later tag for a file
+          ;; tree with no go.mod, the version is considered to be part of the
+          ;; v1 module's available versions and is given an +incompatible
+          ;; suffix
+          ;; (see:https://golang.org/cmd/go/#hdr-Module_compatibility_and_semantic_versioning).
+          (if (string-suffix? "+incompatible" version)
+              (string-drop-right version 13)
+              version))
+         (match (regexp-exec %go-version-rx version)))
+    (if match
+        (match:substring match 4)
+        version)))
+
 (define %go-build-system-modules
   ;; Build-side modules imported and used by default.
   `((guix build go-build-system)