records: Add `recutils->alist' for public consumption.

* guix/records.scm (%recutils-field-rx): New variable.
  (recutils->alist): New procedure, formerly known as `fields->alist'.
* guix/scripts/substitute-binary.scm (fields->alist): Use it.
* tests/records.scm ("recutils->alist"): New test.

guix/records.scm

@@ -21,9 +21,12 @@
   #:use-module (srfi srfi-9)
   #:use-module (srfi srfi-26)
   #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
+  #:use-module (ice-9 rdelim)
   #:export (define-record-type*
             alist->record
-            object->fields))
+            object->fields
+            recutils->alist))
 
 ;;; Commentary:
 ;;;
@@ -211,4 +214,24 @@ PORT, according to FIELDS.  FIELDS must be a list of field name/getter pairs."
        (format port "~a: ~a~%" field (get object))
        (loop rest)))))
 
+(define %recutils-field-rx
+  (make-regexp "^([[:graph:]]+): (.*)$"))
+
+(define (recutils->alist port)
+  "Read a recutils-style record from PORT and return it as a list of key/value
+pairs.  Stop upon an empty line (after consuming it) or EOF."
+  (let loop ((line   (read-line port))
+             (result '()))
+    (cond ((or (eof-object? line) (string-null? line))
+           (reverse result))
+          ((regexp-exec %recutils-field-rx line)
+           =>
+           (lambda (match)
+             (loop (read-line port)
+                   (alist-cons (match:substring match 1)
+                               (match:substring match 2)
+                               result))))
+          (else
+           (error "unmatched line" line)))))
+
 ;;; records.scm ends here

guix/scripts/substitute-binary.scm

@@ -102,23 +102,8 @@ output port, and PROC's result is returned."
 (define (fields->alist port)
   "Read recutils-style record from PORT and return them as a list of key/value
 pairs."
-  (define field-rx
+  (with-mutex %regexp-exec-mutex
-    (make-regexp "^([[:graph:]]+): (.*)$"))
+    (recutils->alist port)))
-
-  (let loop ((line   (read-line port))
-             (result '()))
-    (cond ((eof-object? line)
-           (reverse result))
-          ((with-mutex %regexp-exec-mutex
-             (regexp-exec field-rx line))
-           =>
-           (lambda (match)
-             (loop (read-line port)
-                   (alist-cons (match:substring match 1)
-                               (match:substring match 2)
-                               result))))
-          (else
-           (error "unmatched line" line)))))
 
 (define %fetch-timeout
   ;; Number of seconds after which networking is considered "slow".

tests/records.scm

@@ -131,6 +131,23 @@
              (parameterize ((mark (cons 'a 'b)))
                (eq? (foo-baz y) (mark))))))))
 
+(test-equal "recutils->alist"
+  '((("Name" . "foo")
+     ("Version" . "0.1")
+     ("Synopsis" . "foo bar")
+     ("Something_else" . "chbouib"))
+    (("Name" . "bar")
+     ("Version" . "1.5")))
+  (let ((p (open-input-string "Name: foo
+Version: 0.1
+Synopsis: foo bar
+Something_else: chbouib
+
+Name: bar
+Version: 1.5")))
+    (list (recutils->alist p)
+          (recutils->alist p))))
+
 (test-end)