Subject: [PATCH v3 2/3] guix: scripts: Add hint for option typo.

From: zimoun <[email-masked]>
Date: Tue, 19 Jan 2021 22:28:09 +0100

* guix/scripts.scm (option-hint): New procedure.
(parse-command-line): Add 'option-hint'.
---
 guix/scripts.scm | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/guix/scripts.scm b/guix/scripts.scm
index 34cba35401..e997edbb6d 100644
--- a/guix/scripts.scm
+++ b/guix/scripts.scm
@@ -4,6 +4,7 @@
 ;;; Copyright © 2015, 2016 Alex Kost <[email-masked]>
 ;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <[email-masked]>
 ;;; Copyright © 2021 Ricardo Wurmus <[email-masked]>
+;;; Copyright © 2021 Simon Tournier <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -112,6 +113,13 @@ procedure, but both the category and synopsis are meant to be read (parsed) by
          doc
          body ...)))))
 
+(define (option-hint guess options)
+  "Return the closest long-name OPTIONS from GUESS,
+according to'string-distance'."
+  (define (options->long-names options)
+    (filter string? (append-map option-names options)))
+  (string-closest guess (options->long-names options) #:threshold 3))
+
 (define (args-fold* args options unrecognized-option-proc operand-proc . seeds)
   "A wrapper on top of `args-fold' that does proper user-facing error
 reporting."
@@ -149,7 +157,11 @@ parameter of 'args-fold'."
     ;; Actual parsing takes place here.
     (apply args-fold* args options
            (lambda (opt name arg . rest)
-             (leave (G_ "~A: unrecognized option~%") name))
+             (let ((hint (option-hint name options)))
+               (when hint
+                (display-hint
+                 (format #f (G_ "Do you mean @code{~a}?~%") hint)))
+               (leave (G_ "~A: unrecognized option~%") name)))
            argument-handler
            seeds))
 
-- 
2.29.2