[bug#71697] [PATCH v5 1/3] scripts: lint: Add 'dry-run' option.

[Simon Tournier <zimon.toutoune@gmail.com>]

* guix/scripts/lint.scm (guix-lint)[show-package-checkers]: New procedure.
(show-help, %options): Add 'dry-run' option.
* doc/guix.texi: Document it.

Change-Id: I8c96e376d52c0961ccf2ab39f1fc856c762b089d
---
 doc/guix.texi         |  3 +++
 guix/scripts/lint.scm | 54 +++++++++++++++++++++++++++++++++++++++----
 2 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 5b77c84b4a..6043962038 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -15463,6 +15463,9 @@ Invoking guix lint
 List and describe all the available checkers that will be run on packages
 and exit.
 
+@item --dry-run
+Do not run the checkers.
+
 @item --checkers
 @itemx -c
 Only enable the checkers specified in a comma-separated list using the
diff --git a/guix/scripts/lint.scm b/guix/scripts/lint.scm
index ee3de51fb1..10abb05cf0 100644
--- a/guix/scripts/lint.scm
+++ b/guix/scripts/lint.scm
@@ -100,6 +100,8 @@ (define (show-help)
   (display (G_ "Usage: guix lint [OPTION]... [PACKAGE]...
 Run a set of checkers on the specified package; if none is specified,
 run the checkers on all packages.\n"))
+  (display (G_ "
+      --dry-run          do not run checkers "))
   (display (G_ "
   -c, --checkers=CHECKER1,CHECKER2...
                          only run the specified checkers"))
@@ -154,6 +156,9 @@ (define %options
         (option '(#\n "no-network") #f #f
                 (lambda (opt name arg result)
                   (alist-cons 'no-network? #t result)))
+        (option '("dry-run") #f #f
+                (lambda (opt name arg result)
+                  (alist-cons 'dry-run? #t result)))
         (find (lambda (option)
                 (member "load-path" (option-names option)))
               %standard-build-options)
@@ -218,14 +223,55 @@ (define-command (guix-lint . args)
                 (proc store))
               (proc #f)))
 
+        (define (show-package-checkers package checkers)
+          (let* ((name (package-name package))
+                 (version (package-version package))
+                 (loc (package-location package))
+                 (number-checkers (length checkers))
+                 (number-all-checkers (length %all-checkers)))
+            (cond
+             ((= number-all-checkers number-checkers)
+              (info loc (G_ "~a@~a: all the ~d checkers would run.~%")
+                    name version
+                    number-all-checkers))
+             ((= 0 number-checkers)
+              (info loc (G_ "~a@~a: none of ~d checkers would run~%")
+                    name version
+                    number-all-checkers))
+             (else
+              (let* ((excluded-checkers (lset-difference eq? %all-checkers checkers))
+                     (number-excluded-checkers (length excluded-checkers))
+                     (number-difference (- number-all-checkers number-excluded-checkers))
+                     (sorter (lambda (list-checkers)
+                               (sort (map (compose symbol->string lint-checker-name)
+                                          list-checkers)
+                                     string<?))))
+                (info loc (G_ "~a@~a: ~d/~d checkers would run")
+                      name version
+                      number-checkers
+                      number-all-checkers)
+                (if (< number-excluded-checkers number-difference)
+                    (format (current-error-port)
+                            (G_ " at the exclusion of:~{ ~a~}.~%")
+                            (sorter excluded-checkers))
+                    (format (current-error-port)
+                            ":~{ ~a~}.~%"
+                            (sorter checkers))))))))
+
         (call-maybe-with-store
          (lambda (store)
            (cond
             ((null? args)
-             (fold-packages (lambda (p r) (run-checkers p checkers
-                                                        #:store store)) '()))
+             (when (assoc-ref opts 'dry-run?)
+               (leave (G_ "too much information to display, did nothing and exit~%") ""))
+             (fold-packages (lambda (p r)
+                              (unless (assoc-ref opts 'dry-run?)
+                                  (run-checkers p checkers
+                                                #:store store))) '()))
             (else
              (for-each (lambda (package)
-                         (run-checkers package checkers
-                                       #:store store))
+                         (if (assoc-ref opts 'dry-run?)
+                             (show-package-checkers package checkers)
+                             (run-checkers package checkers
+                                           #:store store)))
                        args)))))))))
-- 
2.41.0