ui: Gracefully report failures to connect to the daemon.

* guix/store.scm (&nix-connection-error): New condition type.
  (open-connection): Translate `system-error' during the `connect' call
  into `&nix-connection-error'.
* guix/ui.scm (call-with-error-handling): Add case for `nix-connection-error?'.
* guix/scripts/package.scm (guix-package): Move `open-connection' call
  within `with-error-handling'.
* guix/scripts/pull.scm (guix-pull): Likewise.
* guix/scripts/download.scm (guix-download): Move body within
  `with-error-handling'.

3 files changed, 29 insertions, 28 deletions

diff --git a/guix/scripts/download.scm b/guix/scripts/download.scm
index 3dc227fdcd..3f989a3494 100644
--- a/guix/scripts/download.scm
+++ b/guix/scripts/download.scm
@@ -110,26 +110,27 @@ and the hash of its contents.\n"))
                  (alist-cons 'argument arg result))
                %default-options))
 
-  (let* ((opts  (parse-options))
-         (store (open-connection))
-         (arg   (assq-ref opts 'argument))
-         (uri   (or (string->uri arg)
-                    (leave (_ "guix-download: ~a: failed to parse URI~%")
-                           arg)))
-         (path  (case (uri-scheme uri)
-                  ((file)
-                   (add-to-store store (basename (uri-path uri))
-                                 #f "sha256" (uri-path uri)))
-                  (else
-                   (fetch-and-store store
-                                    (cut url-fetch arg <>
-                                         #:mirrors %mirrors)
-                                    (basename (uri-path uri))))))
-         (hash  (call-with-input-file
-                    (or path
-                        (leave (_ "guix-download: ~a: download failed~%")
-                               arg))
-                  (compose sha256 get-bytevector-all)))
-         (fmt   (assq-ref opts 'format)))
-    (format #t "~a~%~a~%" path (fmt hash))
-    #t))
+  (with-error-handling
+    (let* ((opts  (parse-options))
+           (store (open-connection))
+           (arg   (assq-ref opts 'argument))
+           (uri   (or (string->uri arg)
+                      (leave (_ "guix-download: ~a: failed to parse URI~%")
+                             arg)))
+           (path  (case (uri-scheme uri)
+                    ((file)
+                     (add-to-store store (basename (uri-path uri))
+                                   #f "sha256" (uri-path uri)))
+                    (else
+                     (fetch-and-store store
+                                      (cut url-fetch arg <>
+                                           #:mirrors %mirrors)
+                                      (basename (uri-path uri))))))
+           (hash  (call-with-input-file
+                      (or path
+                          (leave (_ "guix-download: ~a: download failed~%")
+                                 arg))
+                    (compose sha256 get-bytevector-all)))
+           (fmt   (assq-ref opts 'format)))
+      (format #t "~a~%~a~%" path (fmt hash))
+      #t)))
diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index dd7d6ca112..a9ed79184e 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -712,8 +712,8 @@ Install, remove, or upgrade PACKAGES in a single transaction.\n"))
 
   (let ((opts (parse-options)))
     (or (process-query opts)
-        (parameterize ((%store (open-connection)))
-          (with-error-handling
+        (with-error-handling
+          (parameterize ((%store (open-connection)))
             (parameterize ((%guile-for-build
                             (package-derivation (%store)
                                                 (if (assoc-ref opts 'bootstrap?)
diff --git a/guix/scripts/pull.scm b/guix/scripts/pull.scm
index 942bf501c5..bc72dc4088 100644
--- a/guix/scripts/pull.scm
+++ b/guix/scripts/pull.scm
@@ -194,9 +194,9 @@ Download and deploy the latest version of Guix.\n"))
                  (leave (_ "~A: unexpected argument~%") arg))
                %default-options))
 
-  (let ((opts  (parse-options))
-        (store (open-connection)))
-    (with-error-handling
+  (with-error-handling
+    (let ((opts  (parse-options))
+          (store (open-connection)))
       (let ((tarball (download-and-store store)))
         (unless tarball
           (leave (_ "failed to download up-to-date source, exiting\n")))