nar: Add support for symlinks.

* guix/nar.scm (write-file): Add case for type `symlink'.
  (restore-file): Likewise.
* tests/nar.scm (random-file-size, make-file-tree, delete-file-tree,
  with-file-tree, file-tree-equal?, make-random-bytevector,
  populate-file): New procedures.
  (%test-dir): New variable.
  ("write-file + restore-file"): Use `%test-dir' and `file-tree-equal?'.
  ("write-file + restore-file with symlinks"): New test.

2 files changed, 169 insertions, 37 deletions

diff --git a/guix/nar.scm b/guix/nar.scm
index 9ae76ff2a9..29b57dc989 100644
--- a/guix/nar.scm
+++ b/guix/nar.scm
@@ -161,6 +161,11 @@ sub-directories of FILE as needed."
                          (dump f)
                          (write-string ")" p)))
                      entries)))
+        ((symlink)
+         (write-string "type" p)
+         (write-string "symlink" p)
+         (write-string "target" p)
+         (write-string (readlink f) p))
         (else
          (raise (condition (&message (message "ENOSYS"))
                            (&nar-error)))))
@@ -178,14 +183,26 @@ Restore it as FILE."
                                    (file #f))))))
 
   (let restore ((file file))
+    (define (read-eof-marker)
+      (match (read-string port)
+        (")" #t)
+        (x (raise
+            (condition
+             (&message (message "invalid nar end-of-file marker"))
+             (&nar-read-error (port port) (file file) (token x)))))))
+
     (match (list (read-string port) (read-string port) (read-string port))
       (("(" "type" "regular")
        (call-with-output-file file (cut read-contents port <>))
-       (match (read-string port)
-         (")" #t)
+       (read-eof-marker))
+      (("(" "type" "symlink")
+       (match (list (read-string port) (read-string port))
+         (("target" target)
+          (symlink target file)
+          (read-eof-marker))
          (x (raise
              (condition
-              (&message (message "invalid nar end-of-file marker"))
+              (&message (message "invalid symlink tokens"))
               (&nar-read-error (port port) (file file) (token x)))))))
       (("(" "type" "directory")
        (let ((dir file))
diff --git a/tests/nar.scm b/tests/nar.scm
index 2d9bffd487..4321cbda53 100644
--- a/tests/nar.scm
+++ b/tests/nar.scm
@@ -22,10 +22,122 @@
   #:use-module (rnrs io ports)
   #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-64)
-  #:use-module (ice-9 ftw))
+  #:use-module (ice-9 ftw)
+  #:use-module (ice-9 match))
 
 ;; Test the (guix nar) module.
 
+
+;;;
+;;; File system testing tools, initially contributed to Guile, then libchop.
+;;;
+
+(define (random-file-size)
+  (define %average (* 1024 512))                  ; 512 KiB
+  (define %stddev  (* 1024 64))                   ; 64 KiB
+  (inexact->exact
+   (max 0 (round (+ %average (* %stddev (random:normal)))))))
+
+(define (make-file-tree dir tree)
+  "Make file system TREE at DIR."
+  (let loop ((dir  dir)
+             (tree tree))
+    (define (scope file)
+      (string-append dir "/" file))
+
+    (match tree
+      (('directory name (body ...))
+       (mkdir (scope name))
+       (for-each (cute loop (scope name) <>) body))
+      (('directory name (? integer? mode) (body ...))
+       (mkdir (scope name))
+       (for-each (cute loop (scope name) <>) body)
+       (chmod (scope name) mode))
+      ((file)
+       (populate-file (scope file) (random-file-size)))
+      ((file (? integer? mode))
+       (populate-file (scope file) (random-file-size))
+       (chmod (scope file) mode))
+      ((from '-> to)
+       (symlink to (scope from))))))
+
+(define (delete-file-tree dir tree)
+  "Delete file TREE from DIR."
+  (let loop ((dir  dir)
+             (tree tree))
+    (define (scope file)
+      (string-append dir "/" file))
+
+    (match tree
+      (('directory name (body ...))
+       (for-each (cute loop (scope name) <>) body)
+       (rmdir (scope name)))
+      (('directory name (? integer? mode) (body ...))
+       (chmod (scope name) #o755)          ; make sure it can be entered
+       (for-each (cute loop (scope name) <>) body)
+       (rmdir (scope name)))
+      ((from '-> _)
+       (delete-file (scope from)))
+      ((file _ ...)
+       (delete-file (scope file))))))
+
+(define-syntax-rule (with-file-tree dir tree body ...)
+  (dynamic-wind
+    (lambda ()
+      (make-file-tree dir 'tree))
+    (lambda ()
+      body ...)
+    (lambda ()
+      (delete-file-tree dir 'tree))))
+
+(define (file-tree-equal? input output)
+  "Return #t if the file trees at INPUT and OUTPUT are equal."
+  (define strip
+    (cute string-drop <> (string-length input)))
+  (define sibling
+    (compose (cut string-append output <>) strip))
+  (define (file=? a b)
+    (and (eq? (stat:type (lstat a)) (stat:type (lstat b)))
+         (case (stat:type (lstat a))
+           ((regular)
+            (equal?
+             (call-with-input-file a get-bytevector-all)
+             (call-with-input-file b get-bytevector-all)))
+           ((symlink)
+            (string=? (readlink a) (readlink b)))
+           (else
+            (error "what?" (lstat a))))))
+
+  (file-system-fold (const #t)
+                    (lambda (name stat result)    ; leaf
+                      (and result
+                           (file=? name (sibling name))))
+                    (lambda (name stat result)    ; down
+                      result)
+                    (lambda (name stat result)    ; up
+                      result)
+                    (const #f)                    ; skip
+                    (lambda (name stat errno result)
+                      (pk 'error name stat errno)
+                      #f)
+                    (> (stat:nlink (stat output)) 2)
+                    input
+                    lstat))
+
+(define (make-random-bytevector n)
+  (let ((bv (make-bytevector n)))
+    (let loop ((i 0))
+      (if (< i n)
+          (begin
+            (bytevector-u8-set! bv i (random 256))
+            (loop (1+ i)))
+          bv))))
+
+(define (populate-file file size)
+  (call-with-output-file file
+    (lambda (p)
+      (put-bytevector p (make-random-bytevector size)))))
+
 (define (rm-rf dir)
   (file-system-fold (const #t)                    ; enter?
                     (lambda (file stat result)    ; leaf
@@ -39,15 +151,18 @@
                     dir
                     lstat))
 
+(define %test-dir
+  ;; An output directory under $top_builddir.
+  (string-append (dirname (search-path %load-path "configure"))
+                 "/test-nar-" (number->string (getpid))))
+
 
 (test-begin "nar")
 
 (test-assert "write-file + restore-file"
   (let* ((input  (string-append (dirname (search-path %load-path "guix.scm"))
                                 "/guix"))
-         (output (string-append (dirname input)
-                                "/test-nar-"
-                                (number->string (getpid))))
+         (output %test-dir)
          (nar    (string-append output ".nar")))
     (dynamic-wind
       (lambda () #t)
@@ -56,40 +171,40 @@
           (cut write-file input <>))
         (call-with-input-file nar
           (cut restore-file <> output))
-        (let* ((strip   (cute string-drop <> (string-length input)))
-               (sibling (compose (cut string-append output <>) strip))
-               (file=?  (lambda (a b)
-                          (and (eq? (stat:type (lstat a)) (stat:type (lstat b)))
-                               (case (stat:type (lstat a))
-                                 ((regular)
-                                  (equal?
-                                   (call-with-input-file a get-bytevector-all)
-                                   (call-with-input-file b get-bytevector-all)))
-                                 ((symlink)
-                                  (string=? (readlink a) (readlink b)))
-                                 (else
-                                  (error "what?" (lstat a))))))))
-          (file-system-fold (const #t)
-                            (lambda (name stat result) ; leaf
-                              (and result
-                                   (file=? name (sibling name))))
-                            (lambda (name stat result) ; down
-                              result)
-                            (lambda (name stat result) ; up
-                              result)
-                            (const #f)                 ; skip
-                            (lambda (name stat errno result)
-                              (pk 'error name stat errno)
-                              #f)
-                            (> (stat:nlink (stat output)) 2)
-                            input
-                            lstat)))
+        (file-tree-equal? input output))
       (lambda ()
         (false-if-exception (delete-file nar))
-        (false-if-exception (rm-rf output))
-        ))))
+        (false-if-exception (rm-rf output))))))
+
+(test-assert "write-file + restore-file with symlinks"
+  (let ((input (string-append %test-dir ".input")))
+    (mkdir input)
+    (dynamic-wind
+      (const #t)
+      (lambda ()
+        (with-file-tree input
+            (directory "root"
+                       (("reg") ("exe" #o777) ("sym" -> "reg")))
+          (let* ((output %test-dir)
+                 (nar    (string-append output ".nar")))
+            (dynamic-wind
+              (lambda () #t)
+              (lambda ()
+                (call-with-output-file nar
+                  (cut write-file input <>))
+                (call-with-input-file nar
+                  (cut restore-file <> output))
+                (file-tree-equal? input output))
+              (lambda ()
+                (false-if-exception (delete-file nar)))))))
+      (lambda ()
+        (rmdir input)))))
 
 (test-end "nar")
 
 
 (exit (= (test-runner-fail-count (test-runner-current)) 0))
+
+;;; Local Variables:
+;;; eval: (put 'with-file-tree 'scheme-indent-function 2)
+;;; End: