bug#22572: Handling of system 'locale' field needs improvement

bug#22572: Handling of system 'locale' field needs improvement

[Mark H Weaver]

Multiple users on #guix have been bitten by the following error message:

  guix system: error: system locale lacks a definition

and even several seasoned developers on #guix didn't know the answer.

At minimum, the error message should be improved to point to the
relevant documentation.

Better yet, the value of the 'locale' field should be automatically
added to the default value of 'locale-definitions' if it's not already
there.  The overwhelming majority of users set their 'locale' and have
no interest in 'locale-definitions'.

    Regards,
      Mark

bug#22572: Handling of system 'locale' field needs improvement

[Ludovic Courtès]

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Mark H Weaver <mhw@netris.org> skribis:

> Better yet, the value of the 'locale' field should be automatically
> added to the default value of 'locale-definitions' if it's not already
> there.  The overwhelming majority of users set their 'locale' and have
> no interest in 'locale-definitions'.

What about this?  This is not ideal in that it guesses the charset based
on the locale name, which won’t always work (the locale name is supposed
to use the normalized name, like “utf8”, whereas the real name is, say,
“UTF-8”), but it should cover 90% of the use cases.


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diff --git a/doc/guix.texi b/doc/guix.texi
index 66ab384..f35a9fe 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -6452,11 +6452,12 @@ Usually, you will want to specify the default locale for the machine
 using the @code{locale} field of the @code{operating-system} declaration
 (@pxref{operating-system Reference, @code{locale}}).
 
-That locale must be among the @dfn{locale definitions} that are known to
-the system---and these are specified in the @code{locale-definitions}
-slot of @code{operating-system}.  The default value includes locale
-definitions for some widely used locales, but not for all the available
-locales, in order to save space.
+The selected locale is automatically added to the @dfn{locale
+definitions} known to the system.  Additional locale definitions can be
+specified in the @code{locale-definitions} slot of
+@code{operating-system}.  The default value includes locale definitions
+for some widely used locales, but not for all the available locales, in
+order to save space.
 
 If the locale specified in the @code{locale} field is not among the
 definitions listed in @code{locale-definitions}, @command{guix system}
diff --git a/gnu/system.scm b/gnu/system.scm
index d4759a0..324d071 100644
--- a/gnu/system.scm
+++ b/gnu/system.scm
@@ -669,14 +669,25 @@ hardware-related operations as necessary when booting a Linux container."
   "Return the directory containing the locales compiled for the definitions
 listed in OS.  The C library expects to find it under
 /run/current-system/locale."
-  ;; While we're at it, check whether the locale of OS is defined.
-  (unless (member (operating-system-locale os)
-                  (map locale-definition-name
-                       (operating-system-locale-definitions os)))
-    (raise (condition
-            (&message (message "system locale lacks a definition")))))
+  (define name
+    (operating-system-locale os))
 
-  (locale-directory (operating-system-locale-definitions os)
+  (define definitions
+    ;; While we're at it, check whether the locale of OS is defined.
+    (if (member (operating-system-locale os)
+                (map locale-definition-name
+                     (operating-system-locale-definitions os)))
+        (operating-system-locale-definitions os)
+        (cons (match (locale-name->definition name)
+                (#f
+                 (raise (condition
+                         (&message
+                          (message (format #f (_ "~a: invalid locale name")
+                                           name))))))
+                (def def))
+              (operating-system-locale-definitions os))))
+
+  (locale-directory definitions
                     #:libcs (operating-system-locale-libcs os)))
 
 (define (kernel->grub-label kernel)
diff --git a/gnu/system/locale.scm b/gnu/system/locale.scm
index e798827..9d695b3 100644
--- a/gnu/system/locale.scm
+++ b/gnu/system/locale.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2014, 2015 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -33,6 +33,7 @@
             locale-definition-source
             locale-definition-charset
 
+            locale-name->definition
             locale-directory
 
             %default-locale-libcs
@@ -52,6 +53,22 @@
   (charset locale-definition-charset              ;string--e.g., "UTF-8"
            (default "UTF-8")))
 
+(define %not-dot
+  (char-set-complement (char-set #\.)))
+
+(define (locale-name->definition name)
+  "Return a <locale-definition> corresponding to NAME, guessing the charset,
+or #f on failure."
+  (match (string-tokenize name %not-dot)
+    ((source charset)
+     (locale-definition (name name)
+                        (source source)
+                        (charset (if (string-ci=? charset "utf8")
+                                     "UTF-8"
+                                     charset))))
+    (_
+     #f)))
+
 (define* (localedef-command locale
                             #:key (libc (canonical-package glibc)))
   "Return a gexp that runs 'localedef' from LIBC to build LOCALE."

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Thanks,
Ludo’.

bug#22572: Handling of system 'locale' field needs improvement

[Ludovic Courtès]

ludo@gnu.org (Ludovic Courtès) skribis:

> Mark H Weaver <mhw@netris.org> skribis:
>
>> Better yet, the value of the 'locale' field should be automatically
>> added to the default value of 'locale-definitions' if it's not already
>> there.  The overwhelming majority of users set their 'locale' and have
>> no interest in 'locale-definitions'.
>
> What about this?  This is not ideal in that it guesses the charset based
> on the locale name, which won’t always work (the locale name is supposed
> to use the normalized name, like “utf8”, whereas the real name is, say,
> “UTF-8”), but it should cover 90% of the use cases.

I pushed an improved version of the patch as f5582b2.

Ludo’.