profiles: Generate an 'etc/profile' file.

Suggested by 宋文武 <iyzsong@gmail.com>
in <http://bugs.gnu.org/20255>.

* guix/build/profiles.scm (abstract-profile,
  write-environment-variable-definition): New procedures.
  (build-profile): Add #:search-paths parameter.  Create
  OUTPUT/etc/profile.
* guix/profiles.scm (profile-derivation)[builder]: Add 'search-paths'
  variable and pass it to 'build-profile'.  Adjust #:modules argument.
* tests/profiles.scm ("etc/profile"): New test.
* doc/guix.texi (Invoking guix package): Mention etc/profile.

.dir-locals.el

@@ -14,6 +14,7 @@
   ((indent-tabs-mode . nil)
    (eval . (put 'eval-when 'scheme-indent-function 1))
    (eval . (put 'test-assert 'scheme-indent-function 1))
+   (eval . (put 'test-assertm 'scheme-indent-function 1))
    (eval . (put 'test-equal 'scheme-indent-function 1))
    (eval . (put 'test-eq 'scheme-indent-function 1))
    (eval . (put 'call-with-input-string 'scheme-indent-function 1))

doc/guix.texi

@@ -950,6 +950,16 @@ created in @file{$HOME/.guix-profile}.  This symlink always points to the
 current generation of the user's default profile.  Thus, users can add
 @file{$HOME/.guix-profile/bin} to their @code{PATH} environment
 variable, and so on.
+@cindex search paths
+If you are not using the Guix System Distribution, consider adding the
+following lines to your @file{~/.bash_profile} (@pxref{Bash Startup
+Files,,, bash, The GNU Bash Reference Manual}) so that newly-spawned
+shells get all the right environment variable definitions:
+
+@example
+GUIX_PROFILE="$HOME/.guix-profile" \
+source "$HOME/.guix-profile/etc/profile"
+@end example
 
 In a multi-user setup, user profiles are stored in a place registered as
 a @dfn{garbage-collector root}, which @file{$HOME/.guix-profile} points

guix/build/profiles.scm

@@ -18,6 +18,10 @@
 
 (define-module (guix build profiles)
   #:use-module (guix build union)
+  #:use-module (guix build utils)
+  #:use-module (guix search-paths)
+  #:use-module (srfi srfi-26)
+  #:use-module (ice-9 match)
   #:use-module (ice-9 pretty-print)
   #:export (build-profile))
 
@@ -28,14 +32,71 @@
 ;;;
 ;;; Code:
 
+(define (abstract-profile profile)
+  "Return a procedure that replaces PROFILE in VALUE with a reference to the
+'GUIX_PROFILE' environment variable.  This allows users to specify what the
+user-friendly name of the profile is, for instance ~/.guix-profile rather than
+/gnu/store/...-profile."
+  (let ((replacement (string-append "${GUIX_PROFILE:-" profile "}")))
+    (match-lambda
+      ((search-path . value)
+       (let* ((separator (search-path-specification-separator search-path))
+              (items     (string-tokenize* value separator))
+              (crop      (cute string-drop <> (string-length profile))))
+         (cons search-path
+               (string-join (map (lambda (str)
+                                   (string-append replacement (crop str)))
+                                 items)
+                            separator)))))))
+
+(define (write-environment-variable-definition port)
+  "Write the given environment variable definition to PORT."
+  (match-lambda
+    ((search-path . value)
+     (display (search-path-definition search-path value #:kind 'prefix)
+              port)
+     (newline port))))
+
 (define* (build-profile output inputs
-                        #:key manifest)
+                        #:key manifest search-paths)
   "Build a user profile from INPUTS in directory OUTPUT.  Write MANIFEST, an
-sexp, to OUTPUT/manifest."
+sexp, to OUTPUT/manifest.  Create OUTPUT/etc/profile with Bash definitions for
+all the variables listed in SEARCH-PATHS."
+  ;; Make the symlinks.
   (union-build output inputs
                #:log-port (%make-void-port "w"))
+
+  ;; Store meta-data.
   (call-with-output-file (string-append output "/manifest")
     (lambda (p)
-      (pretty-print manifest p))))
+      (pretty-print manifest p)))
+
+  ;; Add a ready-to-use Bash profile.
+  (mkdir-p (string-append output "/etc"))
+  (call-with-output-file (string-append output "/etc/profile")
+    (lambda (port)
+      ;; The use of $GUIX_PROFILE described below is not great.  Another
+      ;; option would have been to use "$1" and have users run:
+      ;;
+      ;;   source ~/.guix-profile/etc/profile ~/.guix-profile
+      ;;
+      ;; However, when 'source' is used with no arguments, $1 refers to the
+      ;; first positional parameter of the calling scripts, so we can rely on
+      ;; it.
+      (display "\
+# Source this file to define all the relevant environment variables in Bash
+# for this profile.  You may want to define the 'GUIX_PROFILE' environment
+# variable to point to the \"visible\" name of the profile, like this:
+#
+#  GUIX_PROFILE=/path/to/profile
+#  source /path/to/profile/etc/profile
+#
+# When GUIX_PROFILE is undefined, the various environment variables refer
+# to this specific profile generation.
+\n" port)
+      (let ((variables (evaluate-search-paths (cons $PATH search-paths)
+                                              (list output))))
+        (for-each (write-environment-variable-definition port)
+                  (map (abstract-profile output) variables))))))
 
 ;;; profile.scm ends here

guix/profiles.scm

@@ -598,17 +598,30 @@ the monadic procedures listed in HOOKS--such as an Info 'dir' file, etc."
 
     (define builder
       #~(begin
-          (use-modules (guix build profiles))
+          (use-modules (guix build profiles)
+                       (guix search-paths))
 
           (setvbuf (current-output-port) _IOLBF)
           (setvbuf (current-error-port) _IOLBF)
 
+          (define search-paths
+            ;; Search paths of MANIFEST's packages, converted back to their
+            ;; record form.
+            (map sexp->search-path-specification
+                 '#$(map search-path-specification->sexp
+                         (append-map manifest-entry-search-paths
+                                     (manifest-entries manifest)))))
+
           (build-profile #$output '#$inputs
-                         #:manifest '#$(manifest->gexp manifest))))
+                         #:manifest '#$(manifest->gexp manifest)
+                         #:search-paths search-paths)))
 
     (gexp->derivation "profile" builder
-                      #:modules '((guix build union)
-                                  (guix build profiles))
+                      #:modules '((guix build profiles)
+                                  (guix build union)
+                                  (guix build utils)
+                                  (guix search-paths)
+                                  (guix records))
                       #:local-build? #t)))
 
 (define (profile-regexp profile)

tests/profiles.scm

@@ -29,6 +29,8 @@
   #:use-module ((gnu packages guile) #:prefix packages:)
   #:use-module (ice-9 match)
   #:use-module (ice-9 regex)
+  #:use-module (ice-9 popen)
+  #:use-module (rnrs io ports)
   #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-64))
 
@@ -220,6 +222,30 @@
                            (manifest-entry-search-paths entry)
                            (package-native-search-paths
                             packages:guile-2.0)))))))))
+
+(test-assertm "etc/profile"
+  ;; Make sure we get an 'etc/profile' file that at least defines $PATH.
+  (mlet* %store-monad
+      ((guile ->   (package
+                     (inherit %bootstrap-guile)
+                     (native-search-paths
+                      (package-native-search-paths packages:guile-2.0))))
+       (entry ->   (package->manifest-entry guile))
+       (drv        (profile-derivation (manifest (list entry))
+                                       #:hooks '()))
+       (profile -> (derivation->output-path drv)))
+    (mbegin %store-monad
+      (built-derivations (list drv))
+      (let* ((pipe (open-input-pipe
+                    (string-append "source "
+                                   profile "/etc/profile; "
+                                   "unset GUIX_PROFILE; set")))
+             (env  (get-string-all pipe)))
+        (return
+         (and (zero? (close-pipe pipe))
+              (string-contains env
+                               (string-append "PATH=" profile "/bin"))))))))
+
 (test-end "profiles")