perform-download: Allow use of ‘download-nar’ for ‘--check’ builds.

Previously, the nar fallback would always fail on ‘--check’ build
because the output directory in that case is different from the store
file name.  This change fixes that.

* guix/build/git.scm (git-fetch-with-fallback): Add #:item parameter and
pass it to ‘download-nar’.
* guix/scripts/perform-download.scm (perform-git-download): Pass #:item
to ‘git-fetch-with-fallback’.

Change-Id: I30fc948718e99574005150bba5215a51ef153c49

2 files changed, 11 insertions, 6 deletions

diff --git a/guix/build/git.scm b/guix/build/git.scm
index 4c69365a7b..a135026fae 100644
--- a/guix/build/git.scm
+++ b/guix/build/git.scm
@@ -92,19 +92,21 @@ fetched, recursively.  Return #t on success, #f otherwise."
 
 
 (define* (git-fetch-with-fallback url commit directory
-                                  #:key (git-command "git")
+                                  #:key (item directory)
+                                  (git-command "git")
                                   hash hash-algorithm
                                   lfs? recursive?)
   "Like 'git-fetch', fetch COMMIT from URL into DIRECTORY, but fall back to
-alternative methods when fetching from URL fails: attempt to download a nar,
-and if that also fails, download from the Software Heritage archive.  When
-HASH and HASH-ALGORITHM are provided, they are interpreted as the nar hash of
-the directory of interested and are used as its content address at SWH."
+alternative methods when fetching from URL fails: attempt to download a nar
+for ITEM, and if that also fails, download from the Software Heritage archive.
+When HASH and HASH-ALGORITHM are provided, they are interpreted as the nar
+hash of the directory of interested and are used as its content address at
+SWH."
   (or (git-fetch url commit directory
                  #:lfs? lfs?
                  #:recursive? recursive?
                  #:git-command git-command)
-      (download-nar directory)
+      (download-nar item directory)
 
       ;; As a last resort, attempt to download from Software Heritage.
       ;; Disable X.509 certificate verification to avoid depending
diff --git a/guix/scripts/perform-download.scm b/guix/scripts/perform-download.scm
index e7eb3b2a1f..b96959a09e 100644
--- a/guix/scripts/perform-download.scm
+++ b/guix/scripts/perform-download.scm
@@ -114,10 +114,13 @@ Note: OUTPUT may differ from the 'out' value of DRV, notably for 'bmCheck' or
       ;; on ambient authority, hence the PATH value below.
       (setenv "PATH" "/run/current-system/profile/bin:/bin:/usr/bin")
 
+      ;; Note: When doing a '--check' build, DRV-OUTPUT and OUTPUT are
+      ;; different, hence the #:item argument below.
       (git-fetch-with-fallback url commit output
                                #:hash hash
                                #:hash-algorithm algo
                                #:recursive? recursive?
+                               #:item (derivation-output-path drv-output)
                                #:git-command %git))))
 
 (define (assert-low-privileges)