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From: "Colin Woodbury" <colin@fosskers.ca>
To: emacs-devel@gnu.org
Subject: [PATCH] lisp/files.el: Add `file-name-set-extension`
Date: Tue, 25 May 2021 08:50:10 -0700	[thread overview]
Message-ID: <6ff4b7d7-03ac-48d1-8d49-de66431d4e5b@www.fastmail.com> (raw)


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This patch adds a safe way to set a filename's extension. It sanitizes the input so that both these cases do the expected thing:

ELISP> (file-name-set-extension "jack.scss" "css")
"jack.css"

ELISP> (file-name-set-extension "jack.scss" ".css")
"jack.css"

Note that if we're trying to be safe with errors, nils, and empty strings, it's not sufficient to just `(concat (file-name-sans-extension file) "." extension)`.

Cheers!

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diff --git a/lisp/files.el b/lisp/files.el
index 62e1702fdf..f8aefa7930 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -4889,6 +4889,20 @@ extension, the value is \"\"."
         (if period
             "")))))
 
+(defun file-name-set-extension (filename extension)
+  "Change the extension of a FILENAME to EXTENSION.
+Sanitizes the input to consolidate leading/trailing dots.
+
+Returns `nil' if either of the FILENAME or EXTENSION are `nil'
+before sanitizing, or empty afterwards."
+  (when (and filename extension)
+    (let* ((patt "[ \\t\\n\\r.]+") ; Borrowed from `string-trim'.
+           (filename (string-trim-right filename patt))
+           (extension (string-trim-left extension patt)))
+      (unless (or (string-empty-p filename)
+                  (string-empty-p extension))
+        (concat (file-name-sans-extension filename) "." extension)))))
+
 (defun file-name-base (&optional filename)
   "Return the base name of the FILENAME: no directory, no extension."
   (declare (advertised-calling-convention (filename) "27.1"))

             reply	other threads:[~2021-05-25 15:50 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-25 15:50 Colin Woodbury [this message]
2021-05-25 17:48 ` [PATCH] lisp/files.el: Add `file-name-set-extension` Andreas Schwab
2021-05-25 19:42   ` Colin Woodbury
2021-05-25 18:00 ` Basil L. Contovounesios
2021-05-25 19:45   ` Colin Woodbury
2021-05-25 20:25     ` Stefan Monnier
2021-05-25 21:21       ` Colin Woodbury
2021-05-25 21:29         ` Stefan Monnier
2021-05-25 21:44           ` Colin Woodbury
2021-05-26  7:34             ` Andreas Schwab
2021-05-26 16:31               ` Colin Woodbury
2021-05-26 17:39                 ` Andreas Schwab
2021-05-31  1:16                   ` Colin Woodbury
2021-06-04 13:08                     ` Philipp
     [not found]                       ` <26B660D9-AC76-4AFC-9FFD-2F5D4DCA16C1@acm.org>
2021-06-09 20:54                         ` Colin Woodbury
2021-06-09 23:05                           ` Stefan Monnier
2021-06-10  0:42                             ` Colin Woodbury
2021-06-10  2:45                               ` Colin Woodbury
2021-06-10  7:46                           ` Michael Albinus
2021-06-10 14:40                             ` Colin Woodbury
2021-06-16  1:15                               ` Colin Woodbury
2021-06-19  9:16                                 ` Michael Albinus

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