From 9c9982dc0c8c38ce3821b154b7e92509c1564317 Mon Sep 17 00:00:00 2001
From: Ludovic Courtès <ludo@gnu.org>
Date: Sun, 17 Nov 2019 23:10:34 +0100
Subject: guix build: Handle "guix build /….drv" correctly for non-existent
 derivations.
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This lets the daemon substitute missing derivations, as in the example
at <https://bugs.gnu.org/38226>, instead of failing with ENOENT.

* guix/scripts/build.scm (options->things-to-build): In the
'derivation-path?' case, don't fail when 'read-derivation-from-file'
raises to ENOENT; return the empty list in that case.
(guix-build): Add non-existent '.drv' files to ITEMS.
Pass ITEMS in addition to DRV to 'build-derivations'.
* tests/guix-build.sh: Add test.
---
 guix/scripts/build.scm | 19 ++++++++++++++++---
 tests/guix-build.sh    |  7 +++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/guix/scripts/build.scm b/guix/scripts/build.scm
index 9ad7379bbe..ae78df9c5c 100644
--- a/guix/scripts/build.scm
+++ b/guix/scripts/build.scm
@@ -802,7 +802,15 @@ build---packages, gexps, derivations, and so on."
   (append-map (match-lambda
                 (('argument . (? string? spec))
                  (cond ((derivation-path? spec)
-                        (list (read-derivation-from-file spec)))
+                        (catch 'system-error
+                          (lambda ()
+                            (list (read-derivation-from-file spec)))
+                          (lambda args
+                            ;; Non-existent .drv files can be substituted down
+                            ;; the road, so don't error out.
+                            (if (= ENOENT (system-error-errno args))
+                                '()
+                                (apply throw args)))))
                        ((store-path? spec)
                         ;; Nothing to do; maybe for --log-file.
                         '())
@@ -934,7 +942,11 @@ needed."
                                    '())))
                    (items (filter-map (match-lambda
                                         (('argument . (? store-path? file))
-                                         (and (not (derivation-path? file))
+                                         ;; If FILE is a .drv that's not in
+                                         ;; store, keep it so that it can be
+                                         ;; substituted.
+                                         (and (or (not (derivation-path? file))
+                                                  (not (file-exists? file)))
                                               file))
                                         (_ #f))
                                       opts))
@@ -965,7 +977,8 @@ needed."
                                (map (compose list derivation-file-name) drv)
                                roots))
                     ((not (assoc-ref opts 'dry-run?))
-                     (and (build-derivations store drv mode)
+                     (and (build-derivations store (append drv items)
+                                             mode)
                           (for-each show-derivation-outputs drv)
                           (for-each (cut register-root store <> <>)
                                     (map (lambda (drv)
diff --git a/tests/guix-build.sh b/tests/guix-build.sh
index 62cdd5fe14..21b6af4395 100644
--- a/tests/guix-build.sh
+++ b/tests/guix-build.sh
@@ -42,6 +42,13 @@ out="`guix build "$drv"`"
 out2="`guix build -e '(@@ (gnu packages bootstrap) %bootstrap-guile)'`"
 test "$out" = "$out2"
 
+# Passing the name of a .drv that doesn't exist.  The daemon should try to
+# substitute the .drv.  Here we just look for the "cannot build missing
+# derivation" error that indicates that the daemon did try to substitute the
+# .drv.
+guix build "$NIX_STORE_DIR/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-foo.drv" 2>&1 \
+    | grep "missing derivation"
+
 # Passing a URI.
 GUIX_DAEMON_SOCKET="file://$GUIX_STATE_DIRECTORY/daemon-socket/socket"	\
 guix build -e '(@@ (gnu packages bootstrap) %bootstrap-guile)'
-- 
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