weather: Add ‘-e’.

* guix/scripts/weather.scm (show-help, %options): Add ‘-e’.
(guix-weather): Handle it.
* doc/guix.texi (Invoking guix weather): Document it.

Change-Id: I6dc97ec2b8226b57be33247b05a34c23b573a64f

doc/guix.texi

@@ -22,7 +22,7 @@
 @set SUBSTITUTE-URLS https://@value{SUBSTITUTE-SERVER-1} https://@value{SUBSTITUTE-SERVER-2}
 
 @copying
-Copyright @copyright{} 2012-2023 Ludovic Courtès@*
+Copyright @copyright{} 2012-2024 Ludovic Courtès@*
 Copyright @copyright{} 2013, 2014, 2016 Andreas Enge@*
 Copyright @copyright{} 2013 Nikita Karetnikov@*
 Copyright @copyright{} 2014, 2015, 2016 Alex Kost@*
@@ -16744,6 +16744,20 @@ guix package}).
 This option can be repeated several times, in which case the manifests
 are concatenated.
 
+@item --expression=@var{expr}
+@itemx -e @var{expr}
+Consider the package @var{expr} evaluates to.
+
+A typical use case for this option is specifying a package that is
+hidden and thus cannot be referred to in the usual way, as in this
+example:
+
+@example
+guix weather -e '(@@@@ (gnu packages rust) rust-bootstrap)'
+@end example
+
+This option can be repeated.
+
 @item --coverage[=@var{count}]
 @itemx -c [@var{count}]
 Report on substitute coverage for packages: list packages with at least

guix/scripts/weather.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2017-2023 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2017-2024 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2018 Kyle Meyer <kyle@kyleam.com>
 ;;; Copyright © 2020 Simon Tournier <zimon.toutoune@gmail.com>
@@ -388,6 +388,8 @@ Report the availability of substitutes.\n"))
   -m, --manifest=MANIFEST
                          look up substitutes for packages specified in MANIFEST"))
   (display (G_ "
+  -e, --expression=EXPR  build the object EXPR evaluates to"))
+  (display (G_ "
   -c, --coverage[=COUNT]
                          show substitute coverage for packages with at least
                          COUNT dependents"))
@@ -426,6 +428,9 @@ Report the availability of substitutes.\n"))
          (option '(#\m "manifest") #t #f
                  (lambda (opt name arg result)
                    (alist-cons 'manifest arg result)))
+         (option '(#\e "expression") #t #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'expression arg result)))
          (option '(#\c "coverage") #f #t
                  (lambda (opt name arg result)
                    (alist-cons 'coverage
@@ -611,6 +616,8 @@ SERVER.  Display information for packages with at least THRESHOLD dependents."
           (base  (filter-map (match-lambda
                                (('argument . spec)
                                 (specification->package spec))
+                               (('expression . str)
+                                (read/eval-package-expression str))
                                (_
                                 #f))
                              opts)))