derivations: Raise an error when a module file is not found.

Suggested by Jookia.

* guix/derivations.scm (&file-search-error): New error condition.
(search-path*): Raise it when 'search-path' returns #f.
* guix/gexp.scm (search-path*): Remove.
* guix/ui.scm (call-with-error-handling): Add case for
'file-search-error?'.
* tests/derivations.scm ("build-expression->derivation and invalid
module name"): New test.

1 files changed, 17 insertions, 1 deletions

diff --git a/guix/derivations.scm b/guix/derivations.scm
index 2af65b1dc0..2d8584e72d 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -90,7 +90,11 @@
             build-derivations
             built-derivations
 
+            file-search-error?
+            file-search-error-file-name
+            file-search-error-search-path
 
+            search-path*
             module->source-file-name
             build-expression->derivation)
 
@@ -1036,10 +1040,22 @@ system, imported, and appears under FINAL-PATH in the resulting store path."
                                   #:guile-for-build guile
                                   #:local-build? #t)))
 
+;; The "file not found" error condition.
+(define-condition-type &file-search-error &error
+  file-search-error?
+  (file     file-search-error-file-name)
+  (path     file-search-error-search-path))
+
 (define search-path*
   ;; A memoizing version of 'search-path' so 'imported-modules' does not end
   ;; up looking for the same files over and over again.
-  (memoize search-path))
+  (memoize (lambda (path file)
+             "Search for FILE in PATH and memoize the result.  Raise a
+'&file-search-error' condition if it could not be found."
+             (or (search-path path file)
+                 (raise (condition
+                         (&file-search-error (file file)
+                                             (path path))))))))
 
 (define (module->source-file-name module)
   "Return the file name corresponding to MODULE, a Guile module name (a list