[PATCH 2/6] ui: Define and honor '&error-location' and '&fix-hint' conditions.

["Ludovic Courtès" <ludo@gnu.org>]

* guix/utils.scm (&error-location, &fix-hint): New condition types.
* guix/ui.scm (report-load-error): Handle them.
(call-with-error-handling): Honor '&error-location'.
---
 guix/ui.scm    | 23 +++++++++++++++++++----
 guix/utils.scm | 17 +++++++++++++++++
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/guix/ui.scm b/guix/ui.scm
index 40371e471..a1152605e 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -251,10 +251,20 @@ ARGS is the list of arguments received by the 'throw' handler."
                (location->string loc) message)))
     (('srfi-34 obj)
      (if (message-condition? obj)
-         (report-error (G_ "~a~%")
-                       (gettext (condition-message obj)
-                                %gettext-domain))
-         (report-error (G_ "exception thrown: ~s~%") obj)))
+         (if (error-location? obj)
+             (format (current-error-port)
+                     (G_ "~a: error: ~a~%")
+                     (location->string (error-location obj))
+                     (gettext (condition-message obj)
+                              %gettext-domain))
+             (report-error (G_ "~a~%")
+                           (gettext (condition-message obj)
+                                    %gettext-domain)))
+         (report-error (G_ "exception thrown: ~s~%") obj))
+     (when (fix-hint? obj)
+       (format (current-error-port) (G_ "hint: ~a~%")
+               (fill-paragraph (texi->plain-text (condition-fix-hint obj))
+                               (terminal-columns) 8))))
     ((error args ...)
      (report-error (G_ "failed to load '~a':~%") file)
      (apply display-error frame (current-error-port) args))))
@@ -517,6 +527,11 @@ interpreted."
 directories:~{ ~a~}~%")
                     (file-search-error-file-name c)
                     (file-search-error-search-path c)))
+            ((and (error-location? c) (message-condition? c))
+             (format (current-error-port)
+                     (G_ "~a: error: ~a~%")
+                     (location->string (error-location c))
+                     (gettext (condition-message c) %gettext-domain)))
             ((message-condition? c)
              ;; Normally '&message' error conditions have an i18n'd message.
              (leave (G_ "~a~%")
diff --git a/guix/utils.scm b/guix/utils.scm
index eb1ec29b3..c0ffed172 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -28,6 +28,7 @@
   #:use-module (srfi srfi-9)
   #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-26)
+  #:use-module (srfi srfi-35)
   #:use-module (srfi srfi-39)
   #:use-module (ice-9 binary-ports)
   #:autoload   (rnrs io ports) (make-custom-binary-input-port)
@@ -60,6 +61,14 @@
             source-properties->location
             location->source-properties
 
+            &error-location
+            error-location?
+            error-location
+
+            &fix-hint
+            fix-hint?
+            condition-fix-hint
+
             nix-system->gnu-triplet
             gnu-triplet->nix-system
             %current-system
@@ -750,6 +759,14 @@ a location object."
     (column   . ,(location-column loc))
     (filename . ,(location-file loc))))
 
+(define-condition-type &error-location &error
+  error-location?
+  (location  error-location))                     ;<location>
+
+(define-condition-type &fix-hint &condition
+  fix-hint?
+  (hint condition-fix-hint))                      ;string
+
 ;;; Local Variables:
 ;;; eval: (put 'call-with-progress-reporter 'scheme-indent-function 1)
 ;;; End:
-- 
2.15.0