utils: Add find-definition-insertion-location procedure.

* guix/utils.scm (find-definition-insertion-location): Add and export
procedure.
* tests/utils.scm ("find-definition-insertion-location"): Add test.

Change-Id: Ie17e1b4a94790f58518ce121411a38d357f49feb
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

guix/utils.scm

@@ -148,6 +148,7 @@
             edit-expression
             delete-expression
             insert-expression
+            find-definition-insertion-location
 
             filtered-port
             decompressed-port
@@ -513,6 +514,24 @@ SOURCE-PROPERTIES."
                    (string-append expr "\n\n" str))))
     (edit-expression source-properties insert)))
 
+(define (find-definition-insertion-location file term)
+  "Search in FILE for a top-level public definition whose defined term
+alphabetically succeeds TERM. Return the location if found, or #f
+otherwise."
+  (let ((search-term (symbol->string term)))
+    (call-with-input-file file
+      (lambda (port)
+        (do ((syntax (read-syntax port)
+                     (read-syntax port)))
+          ((match (syntax->datum syntax)
+             (('define-public current-term _ ...)
+              (string> (symbol->string current-term)
+                       search-term))
+             ((? eof-object?) #t)
+             (_ #f))
+           (and (not (eof-object? syntax))
+                (syntax-source syntax))))))))
+
 
 ;;;
 ;;; Keyword arguments.

tests/utils.scm

@@ -288,6 +288,20 @@ skip these tests."
                        `(define-public package-1 'package))
     (call-with-input-file temp-file get-string-all)))
 
+(test-equal "find-definition-insertion-location"
+  (list `((filename . ,temp-file) (line . 0) (column . 0))
+        `((filename . ,temp-file) (line . 5) (column . 0))
+        #f)
+  (begin
+    (call-with-output-file temp-file
+      (lambda (port)
+        (display "(define-public package-1\n  'foo)\n\n" port)
+        (display "(define foo 'bar)\n\n" port)
+        (display "(define-public package-2\n  'baz)\n" port)))
+    (map (lambda (term)
+           (find-definition-insertion-location temp-file term))
+         (list 'package 'package-1 'package-2))))
+
 (test-equal "string-distance"
   '(0 1 1 5 5)
   (list