[PATCH] download: Add url-fetch/xz-file.

[Hilton Chain <hako@ultrarare.space>]

* guix/download.scm (url-fetch/xz-file): New variable.
---
 guix/download.scm | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/guix/download.scm b/guix/download.scm
index 2e9ecb43fc..cce62c4185 100644
--- a/guix/download.scm
+++ b/guix/download.scm
@@ -41,6 +41,7 @@ (define-module (guix download)
             (url-fetch* . url-fetch)
             url-fetch/executable
             url-fetch/tarbomb
+            url-fetch/xz-file
             url-fetch/zipbomb
             download-to-store))
 
@@ -602,6 +603,48 @@ (define tar
                       #:graft? #f
                       #:local-build? #t)))
 
+(define* (url-fetch/xz-file url hash-algo hash
+                            #:optional name
+                            #:key (system (%current-system))
+                            (guile (default-guile)))
+  "Similar to 'url-fetch' but decompress the xz file at URL as the result.
+This is mainly used for adding xz-compressed patches to a origin definition."
+  (define file-name
+    (match url
+      ((head _ ...)
+       (basename head))
+      (_
+       (basename url))))
+  (define xz
+    (module-ref (resolve-interface '(gnu packages compression)) 'xz))
+
+  (mlet %store-monad ((drv (url-fetch* url hash-algo hash
+                                       (or name (basename file-name ".xz"))
+                                       #:system system
+                                       #:guile guile))
+                      (guile (package->derivation guile system)))
+    ;; Take the xz file, and simply decompress it.
+    ;; Use ungrafted xz so that the resulting file doesn't depend on whether
+    ;; grafts are enabled.
+    (gexp->derivation (or name file-name)
+                      (with-imported-modules '((guix build utils))
+                        #~(begin
+                            (use-modules (guix build utils))
+                            (setenv "XZ_OPT"
+                                    (string-join (%xz-parallel-args)))
+
+                            (copy-file #$drv #$file-name)
+                            (make-file-writable #$file-name)
+                            (invoke (string-append #+xz "/bin/unxz")
+                                    #$file-name)
+
+                            (copy-file (basename #$file-name ".xz")
+                                       #$output)))
+                      #:system system
+                      #:guile-for-build guile
+                      #:graft? #f
+                      #:local-build? #t)))
+
 (define* (url-fetch/zipbomb url hash-algo hash
                             #:optional name
                             #:key (system (%current-system))

base-commit: 718223c58c20fa066527fb30da2b5dccca82913f
-- 
2.39.1