ui: Add `args-fold*' and use it.

* guix/ui.scm (args-fold*): New procedure.
* guix/scripts/build.scm, guix/scripts/download.scm,
  guix/scripts/gc.scm, guix/scripts/hash.scm, guix/scripts/import.scm,
  guix/scripts/package.scm, guix/scripts/pull.scm,
  guix/scripts/refresh.scm: Use `args-fold*' instead of `args-fold'.

guix/scripts/build.scm

@@ -149,7 +149,7 @@ Build the given PACKAGE-OR-DERIVATION and return their output paths.\n"))
 (define (guix-build . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold args %options
+    (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (_ "~A: unrecognized option~%") name))
                 (lambda (arg result)

guix/scripts/download.scm

@@ -90,7 +90,7 @@ Supported formats: 'nix-base32' (default), 'base32', and 'base16'
 (define (guix-download . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold args %options
+    (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (_ "~A: unrecognized option~%") name))
                 (lambda (arg result)

guix/scripts/gc.scm

@@ -141,7 +141,7 @@ interpreted."
 (define (guix-gc . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold args %options
+    (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (_ "~A: unrecognized option~%") name))
                 (lambda (arg result)

guix/scripts/hash.scm

@@ -90,7 +90,7 @@ Supported formats: 'nix-base32' (default), 'base32', and 'base16'
 (define (guix-hash . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold args %options
+    (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (_ "unrecognized option: ~a~%")
                          name))

guix/scripts/import.scm

@@ -95,7 +95,7 @@ Import and convert the Nix expression ATTRIBUTE of NIXPKGS.\n"))
 (define (guix-import . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold args %options
+    (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (_ "~A: unrecognized option~%") name))
                 (lambda (arg result)

guix/scripts/package.scm

@@ -446,7 +446,7 @@ Install, remove, or upgrade PACKAGES in a single transaction.\n"))
 (define (guix-package . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold args %options
+    (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (_ "~A: unrecognized option~%") name))
                 (lambda (arg result)

guix/scripts/pull.scm

@@ -173,7 +173,7 @@ Download and deploy the latest version of Guix.\n"))
 (define (guix-pull . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold args %options
+    (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (_ "~A: unrecognized option~%") name))
                 (lambda (arg result)

guix/scripts/refresh.scm

@@ -93,7 +93,7 @@ specified with `--select'.\n"))
 (define (guix-refresh . args)
   (define (parse-options)
     ;; Return the alist of option values.
-    (args-fold args %options
+    (args-fold* args %options
                 (lambda (opt name arg result)
                   (leave (_ "~A: unrecognized option~%") name))
                 (lambda (arg result)

guix/ui.scm

@@ -29,6 +29,7 @@
   #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-34)
+  #:use-module (srfi srfi-37)
   #:use-module (ice-9 match)
   #:use-module (ice-9 format)
   #:export (_
@@ -46,6 +47,7 @@
             fill-paragraph
             string->recutils
             package->recutils
+            args-fold*
             run-guix-command
             program-name
             guix-warning-port
@@ -370,6 +372,18 @@ WIDTH columns."
           (and=> (package-description p) description->recutils))
   (newline port))
 
+(define (args-fold* options unrecognized-option-proc operand-proc . seeds)
+  "A wrapper on top of `args-fold' that does proper user-facing error
+reporting."
+  (catch 'misc-error
+    (lambda ()
+      (apply args-fold options unrecognized-option-proc
+             operand-proc seeds))
+    (lambda (key proc msg args . rest)
+      ;; XXX: MSG is not i18n'd.
+      (leave (_ "invalid argument: ~a~%")
+             (apply format #f msg args)))))
+
 (define (show-guix-usage)
   ;; TODO: Dynamically generate a summary of available commands.
   (format (current-error-port)