04/10: packages: Remove duplicates from package cache.

[guix-commits]

civodul pushed a commit to branch master
in repository guix.

commit 36754eee28187b41e9a6ef15cd3c9911449a4e8d
Author: Ludovic Courtès <address@hidden>
Date:   Fri Feb 15 22:58:29 2019 +0100

    packages: Remove duplicates from package cache.
    
    Previously the same package could appear several times if several
    variables were bound to it, as is notably the case for "python"
    currently.  This, in turn, would lead to obnoxious "ambiguous package
    specification" messages.
    
    * gnu/packages.scm (generate-package-cache)[expand-cache]: Change RESULT
    to RESULT+SEEN and adjust accordingly.
    Call 'first' on the result of 'fold-module-public-variables*'.
    * tests/packages.scm ("fold-available-packages with/without cache"):
    Check for lack of duplicates in FROM-CACHE.
---
 gnu/packages.scm   | 53 ++++++++++++++++++++++++++++++-----------------------
 tests/packages.scm |  3 ++-
 2 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/gnu/packages.scm b/gnu/packages.scm
index a181420..7b17e70 100644
--- a/gnu/packages.scm
+++ b/gnu/packages.scm
@@ -371,34 +371,41 @@ reducing the memory footprint."
   (define cache-file
     (string-append directory %package-cache-file))
 
-  (define (expand-cache module symbol variable result)
+  (define (expand-cache module symbol variable result+seen)
     (match (false-if-exception (variable-ref variable))
       ((? package? package)
-       (if (hidden-package? package)
-           result
-           (cons `#(,(package-name package)
-                    ,(package-version package)
-                    ,(module-name module)
-                    ,symbol
-                    ,(package-outputs package)
-                    ,(->bool (member (%current-system)
-                                     (package-supported-systems package)))
-                    ,(->bool (package-superseded package))
-                    ,@(let ((loc (package-location package)))
-                        (if loc
-                            `(,(location-file loc)
-                              ,(location-line loc)
-                              ,(location-column loc))
-                            '(#f #f #f))))
-                 result)))
+       (match result+seen
+         ((result . seen)
+          (if (or (vhash-assq package seen)
+                  (hidden-package? package))
+              (cons result seen)
+              (cons (cons `#(,(package-name package)
+                             ,(package-version package)
+                             ,(module-name module)
+                             ,symbol
+                             ,(package-outputs package)
+                             ,(->bool
+                               (member (%current-system)
+                                       (package-supported-systems package)))
+                             ,(->bool (package-superseded package))
+                             ,@(let ((loc (package-location package)))
+                                 (if loc
+                                     `(,(location-file loc)
+                                       ,(location-line loc)
+                                       ,(location-column loc))
+                                     '(#f #f #f))))
+                          result)
+                    (vhash-consq package #t seen))))))
       (_
-       result)))
+       result+seen)))
 
   (define exp
-    (fold-module-public-variables* expand-cache '()
-                                   (all-modules (%package-module-path)
-                                                #:warn
-                                                warn-about-load-error)))
+    (first
+     (fold-module-public-variables* expand-cache
+                                    (cons '() vlist-null)
+                                    (all-modules (%package-module-path)
+                                                 #:warn
+                                                 warn-about-load-error))))
 
   (mkdir-p (dirname cache-file))
   (call-with-output-file cache-file
diff --git a/tests/packages.scm b/tests/packages.scm
index e5704ae..4e4bffc 100644
--- a/tests/packages.scm
+++ b/tests/packages.scm
@@ -1037,7 +1037,8 @@
                                                       result))
                                               '()))))))
 
-    (lset= equal? no-cache from-cache)))
+    (and (equal? (delete-duplicates from-cache) from-cache)
+         (lset= equal? no-cache from-cache))))
 
 (test-assert "find-packages-by-name"
   (match (find-packages-by-name "hello")