daemon: Allow check builds of 'builtin:download' derivations.

Fixes <http://bugs.gnu.org/25089>.
Reported by Leo Famulari <leo@famulari.name>.

* nix/libstore/build.cc (DerivationGoal::runChild): In the 'isBuiltin'
case, check whether DRV's output is in 'redirectedOutputs', and pass an
'output' argument to the built-in builder.
(DerivationGoal::addHashRewrite): Add 'printMsg' call.
* nix/libstore/builtins.hh (derivationBuilder): Add 'output' parameter.
* nix/libstore/builtins.cc (builtinDownload): Likewise.
Add OUTPUT to ARGV.
* guix/scripts/perform-download.scm (perform-download): Add 'output'
parameter.
(guix-perform-download): Adjust 'match' clauses accordingly.
* tests/derivations.scm ("'download' built-in builder, check mode"): New
test.

5 files changed, 62 insertions, 16 deletions

diff --git a/guix/scripts/perform-download.scm b/guix/scripts/perform-download.scm
index 0d2e7089aa..58a7377141 100644
--- a/guix/scripts/perform-download.scm
+++ b/guix/scripts/perform-download.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -19,7 +19,7 @@
 (define-module (guix scripts perform-download)
   #:use-module (guix ui)
   #:use-module (guix derivations)
-  #:use-module ((guix store) #:select (derivation-path?))
+  #:use-module ((guix store) #:select (derivation-path? store-path?))
   #:use-module (guix build download)
   #:use-module (ice-9 match)
   #:export (guix-perform-download))
@@ -41,10 +41,13 @@
     (module-use! module (resolve-interface '(guix base32)))
     module))
 
-(define (perform-download drv)
-  "Perform the download described by DRV, a fixed-output derivation."
+(define (perform-download drv output)
+  "Perform the download described by DRV, a fixed-output derivation, to
+OUTPUT.
+
+Note: We don't read the value of 'out' in DRV since the actual output is
+different from that when we're doing a 'bmCheck' or 'bmRepair' build."
   (derivation-let drv ((url "url")
-                       (output "out")
                        (executable "executable")
                        (mirrors "mirrors")
                        (content-addressed-mirrors "content-addressed-mirrors"))
@@ -93,18 +96,20 @@ of GnuTLS over HTTPS, before we have built GnuTLS.  See
 <http://bugs.gnu.org/22774>."
   (with-error-handling
     (match args
-      (((? derivation-path? drv))
+      (((? derivation-path? drv) (? store-path? output))
        ;; This program must be invoked by guix-daemon under an unprivileged
        ;; UID to prevent things downloading from 'file:///etc/shadow' or
        ;; arbitrary code execution via the content-addressed mirror
        ;; procedures.  (That means we exclude users who did not pass
        ;; '--build-users-group'.)
        (assert-low-privileges)
-       (perform-download (call-with-input-file drv read-derivation)))
+       (perform-download (call-with-input-file drv read-derivation)
+                         output))
       (("--version")
        (show-version-and-exit))
       (x
-       (leave (_ "fixed-output derivation name expected~%"))))))
+       (leave
+        (_ "fixed-output derivation and output file name expected~%"))))))
 
 ;; Local Variables:
 ;; eval: (put 'derivation-let 'scheme-indent-function 2)
diff --git a/nix/libstore/build.cc b/nix/libstore/build.cc
index 38048ceebc..cebc404d1c 100644
--- a/nix/libstore/build.cc
+++ b/nix/libstore/build.cc
@@ -2271,8 +2271,17 @@ void DerivationGoal::runChild()
                 logType = ltFlat;
 
 		auto buildDrv = lookupBuiltinBuilder(drv.builder);
-                if (buildDrv != NULL)
-                    buildDrv(drv, drvPath);
+                if (buildDrv != NULL) {
+		    /* Check what the output file name is.  When doing a
+		       'bmCheck' build, the output file name is different from
+		       that specified in DRV due to hash rewriting.  */
+		    Path output = drv.outputs["out"].path;
+		    auto redirected = redirectedOutputs.find(output);
+		    if (redirected != redirectedOutputs.end())
+			output = redirected->second;
+
+                    buildDrv(drv, drvPath, output);
+		}
                 else
                     throw Error(format("unsupported builtin function '%1%'") % string(drv.builder, 8));
                 _exit(0);
@@ -2742,6 +2751,8 @@ Path DerivationGoal::addHashRewrite(const Path & path)
     rewritesToTmp[h1] = h2;
     rewritesFromTmp[h2] = h1;
     redirectedOutputs[path] = p;
+    printMsg(lvlChatty, format("output '%1%' redirected to '%2%'")
+	     % path % p);
     return p;
 }
 
diff --git a/nix/libstore/builtins.cc b/nix/libstore/builtins.cc
index 32af767dc4..7ed75e5079 100644
--- a/nix/libstore/builtins.cc
+++ b/nix/libstore/builtins.cc
@@ -1,5 +1,5 @@
 /* GNU Guix --- Functional package management for GNU
-   Copyright (C) 2016 Ludovic Courtès <ludo@gnu.org>
+   Copyright (C) 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 
    This file is part of GNU Guix.
 
@@ -25,7 +25,8 @@
 namespace nix {
 
 static void builtinDownload(const Derivation &drv,
-			    const std::string &drvPath)
+			    const std::string &drvPath,
+			    const std::string &output)
 {
     /* Invoke 'guix perform-download'.  */
     Strings args;
@@ -35,7 +36,10 @@ static void builtinDownload(const Derivation &drv,
     /* Close all other file descriptors. */
     closeMostFDs(set<int>());
 
-    const char *const argv[] = { "download", drvPath.c_str(), NULL };
+    const char *const argv[] =
+      {
+	"download", drvPath.c_str(), output.c_str(), NULL
+      };
 
     /* XXX: Hack our way to use the 'download' script from 'LIBEXECDIR/guix'
        or just 'LIBEXECDIR', depending on whether we're running uninstalled or
diff --git a/nix/libstore/builtins.hh b/nix/libstore/builtins.hh
index 79171fcb6c..396ea14ebc 100644
--- a/nix/libstore/builtins.hh
+++ b/nix/libstore/builtins.hh
@@ -1,5 +1,5 @@
 /* GNU Guix --- Functional package management for GNU
-   Copyright (C) 2016 Ludovic Courtès <ludo@gnu.org>
+   Copyright (C) 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 
    This file is part of GNU Guix.
 
@@ -33,7 +33,8 @@ namespace nix {
 
     /* Build DRV, which lives at DRVPATH.  */
     typedef void (*derivationBuilder) (const Derivation &drv,
-				       const std::string &drvPath);
+				       const std::string &drvPath,
+				       const std::string &output);
 
     /* Return the built-in builder called BUILDER, or NULL if none was
        found.  */
diff --git a/tests/derivations.scm b/tests/derivations.scm
index 2b5aa796d4..3fbfec3793 100644
--- a/tests/derivations.scm
+++ b/tests/derivations.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -279,6 +279,27 @@
       (build-derivations %store (list drv))
       #f)))
 
+(unless (force %http-server-socket)
+  (test-skip 1))
+(test-assert "'download' built-in builder, check mode"
+  ;; Make sure rebuilding the 'builtin:download' derivation in check mode
+  ;; works.  See <http://bugs.gnu.org/25089>.
+  (let* ((text (random-text))
+         (drv (derivation %store "world"
+                          "builtin:download" '()
+                          #:env-vars `(("url"
+                                        . ,(object->string (%local-url))))
+                          #:hash-algo 'sha256
+                          #:hash (sha256 (string->utf8 text)))))
+    (and (with-http-server 200 text
+           (build-derivations %store (list drv)))
+         (with-http-server 200 text
+           (build-derivations %store (list drv)
+                              (build-mode check)))
+         (string=? (call-with-input-file (derivation->output-path drv)
+                     get-string-all)
+                   text))))
+
 (test-equal "derivation-name"
   "foo-0.0"
   (let ((drv (derivation %store "foo-0.0" %bash '())))
@@ -1109,3 +1130,7 @@
          (call-with-input-file out get-string-all))))
 
 (test-end)
+
+;; Local Variables:
+;; eval: (put 'with-http-server 'scheme-indent-function 2)
+;; End: