From: Stefan Kangas <stefankangas@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: visuweshm@gmail.com, thievol@posteo.net, luangruo@yahoo.com,
emacs-devel@gnu.org
Subject: Make format-spec accept a function as the substitution
Date: Tue, 27 Sep 2022 14:02:32 -0400 [thread overview]
Message-ID: <CADwFkm=d5tieKrDSw3F+fPMRmwdMn+nxiEE9k4FAhjF0TL3_2A@mail.gmail.com> (raw)
In-Reply-To: <83tu4sivtq.fsf@gnu.org>
[-- Attachment #1: Type: text/plain, Size: 283 bytes --]
Eli Zaretskii <eliz@gnu.org> writes:
> And then I'd suggest something like
>
> If the substitution for a specification character is a function, the
> function will be called only if FORMAT uses that character.
Thanks. Please find attached a complete patch with documentation.
[-- Attachment #2: 0001-Make-format-spec-support-functions.patch --]
[-- Type: text/x-diff, Size: 4695 bytes --]
From ea1bdcc9710bb730fcf765c55875a6f102089f34 Mon Sep 17 00:00:00 2001
From: Stefan Kangas <stefankangas@gmail.com>
Date: Tue, 27 Sep 2022 18:16:51 +0200
Subject: [PATCH] Make format-spec support functions
* lisp/format-spec.el (format-spec): Allow using a format as the
substitution for a character.
* doc/lispref/strings.texi (Custom Format Strings): Document the
above change.
* test/lisp/format-spec-tests.el (format-spec/function): New test.
Ref. https://lists.gnu.org/r/emacs-devel/2022-09/msg01875.html
---
doc/lispref/strings.texi | 5 +++++
etc/NEWS | 6 ++++++
lisp/format-spec.el | 16 ++++++++++++++--
test/lisp/format-spec-tests.el | 11 +++++++++++
4 files changed, 36 insertions(+), 2 deletions(-)
diff --git a/doc/lispref/strings.texi b/doc/lispref/strings.texi
index 374381e595..af368f5d01 100644
--- a/doc/lispref/strings.texi
+++ b/doc/lispref/strings.texi
@@ -1293,6 +1293,11 @@ Custom Format Strings
the order of associations in @var{spec-alist}.
@end itemize
+REPLACEMENT can also be a function taking no arguments. It will only
+be called when the corresponding LETTER is used in the TEMPLATE. This
+is useful, for example, to avoid prompting for input unless it is
+needed.
+
The optional argument @var{ignore-missing} indicates how to handle
specification characters in @var{template} that are not found in
@var{spec-alist}. If it is @code{nil} or omitted, the function
diff --git a/etc/NEWS b/etc/NEWS
index 99243481a0..97838442db 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -3910,6 +3910,12 @@ the same but works by modifying LIST destructively.
---
** 'string-split' is now an alias for 'split-string'.
++++
+** 'format-spec' now accepts functions in the replacement.
+The function is called only when used in the format string. This is
+useful to avoid side-effects such as prompting, when the value is not
+actually being used for anything.
+
+++
** The variable 'max-specpdl-size' has been made obsolete.
Now 'max-lisp-eval-depth' alone is used for limiting Lisp recursion
diff --git a/lisp/format-spec.el b/lisp/format-spec.el
index 45c19aebc8..1c817ea7fa 100644
--- a/lisp/format-spec.el
+++ b/lisp/format-spec.el
@@ -59,6 +59,17 @@ format-spec
leading zeros or truncating leading characters until it's ten
characters wide\".
+If the substitution for a specification character is a function,
+the function will be called only if FORMAT uses that character.
+For example:
+
+ (format-spec \"%n\"
+ \\=`((?n . ,(lambda ()
+ (read-number \"Number: \")))))
+
+Note that it is best to make sure the function is not quoted,
+like above, so that it is compiled by the byte-compiler.
+
Any text properties of FORMAT are copied to the result, with any
text properties of a %-spec itself copied to its substitution.
@@ -94,14 +105,15 @@ format-spec
(width (match-string 2))
(trunc (match-string 3))
(char (string-to-char (match-string 4)))
- (text (assq char specification)))
+ (text (let ((res (cdr (assq char specification))))
+ (if (functionp res) (funcall res) res))))
(when (and split
(not (= (1- beg) split-start)))
(push (buffer-substring split-start (1- beg)) split-result))
(cond (text
;; Handle flags.
(setq text (format-spec--do-flags
- (format "%s" (cdr text))
+ (format "%s" text)
(format-spec--parse-flags flags)
(and width (string-to-number width))
(and trunc (car (read-from-string trunc 1)))))
diff --git a/test/lisp/format-spec-tests.el b/test/lisp/format-spec-tests.el
index 4a3cc74c33..bd493ae1d7 100644
--- a/test/lisp/format-spec-tests.el
+++ b/test/lisp/format-spec-tests.el
@@ -148,6 +148,17 @@ format-spec
(format-spec fmt '((?b . "asd") (?a . "fgh")))
#("fgh%asdasd" 0 3 (a b) 3 4 (c d) 7 10 (e f))))))
+(ert-deftest format-spec/function ()
+ (let* (called
+ (spec `((?a . "foo")
+ (?f . ,(lambda ()
+ (setq called t)
+ "bar")))))
+ (should (equal (format-spec "%a" spec) "foo"))
+ (should-not called)
+ (should (equal (format-spec "%f" spec) "bar"))
+ (should called)))
+
(ert-deftest format-spec-unknown ()
(should-error (format-spec "foo %b %z zot" '((?b . "bar"))))
(should-error (format-spec "foo %b %%%z zot" '((?b . "bar"))))
--
2.30.2
next prev parent reply other threads:[~2022-09-27 18:02 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <166336105908.23797.12319380359602540227@vcs2.savannah.gnu.org>
[not found] ` <20220916204419.B124FC00872@vcs2.savannah.gnu.org>
2022-09-17 2:00 ` master fe7c015b20: Support XFCE in wallpaper.el Po Lu
2022-09-17 18:03 ` Stefan Kangas
2022-09-18 1:18 ` Po Lu
2022-09-18 2:13 ` Po Lu
2022-09-18 4:48 ` Thierry Volpiatto
2022-09-18 5:15 ` Po Lu
2022-09-18 14:44 ` Thierry Volpiatto
2022-09-19 4:49 ` Po Lu
2022-09-19 6:06 ` Thierry Volpiatto
2022-09-19 7:24 ` Po Lu
2022-09-19 8:40 ` Thierry Volpiatto
2022-09-19 8:52 ` Po Lu
2022-09-19 17:46 ` Thierry Volpiatto
2022-09-19 18:05 ` Thierry Volpiatto
2022-09-19 18:59 ` Stefan Kangas
2022-09-19 20:16 ` Tomas Hlavaty
2022-09-19 21:19 ` Stefan Monnier
2022-09-20 6:16 ` Thierry Volpiatto
2022-09-20 2:32 ` Eli Zaretskii
2022-09-20 2:43 ` Po Lu
2022-09-20 6:25 ` Thierry Volpiatto
2022-09-20 8:22 ` Po Lu
2022-09-19 7:23 ` Thierry Volpiatto
2022-09-26 19:42 ` Stefan Kangas
2022-09-26 21:01 ` Stephen Berman
2022-09-26 22:46 ` Stefan Kangas
2022-09-27 7:17 ` Stephen Berman
2022-09-27 7:45 ` Po Lu
2022-09-27 13:42 ` Stefan Kangas
2022-09-27 0:33 ` Po Lu
2022-09-27 5:56 ` Eli Zaretskii
2022-09-27 6:13 ` Po Lu
2022-09-27 6:45 ` Eli Zaretskii
2022-09-27 7:50 ` Po Lu
2022-09-27 7:56 ` Eli Zaretskii
2022-09-27 8:31 ` Po Lu
2022-09-27 7:21 ` Thierry Volpiatto
2022-09-27 7:42 ` Po Lu
2022-09-27 7:55 ` Thierry Volpiatto
2022-09-27 8:35 ` Po Lu
2022-09-27 18:33 ` Stefan Kangas
2022-09-28 0:34 ` Po Lu
2022-09-27 13:57 ` Stefan Kangas
2022-09-27 15:43 ` Visuwesh
2022-09-27 16:19 ` Stefan Kangas
2022-09-27 16:39 ` Thierry Volpiatto
2022-09-27 16:40 ` Eli Zaretskii
2022-09-27 17:01 ` Stefan Kangas
2022-09-27 17:14 ` Eli Zaretskii
2022-09-27 18:02 ` Stefan Kangas [this message]
2022-09-29 6:57 ` Make format-spec accept a function as the substitution Thierry Volpiatto
2022-09-29 12:36 ` Stefan Monnier
2022-09-29 12:59 ` Stefan Kangas
2022-09-29 15:02 ` Philip Kaludercic
2022-09-29 16:34 ` Stefan Kangas
2022-09-29 16:53 ` Philip Kaludercic
2022-09-29 17:06 ` Stefan Kangas
2022-09-29 16:56 ` Stefan Monnier
2022-09-29 15:09 ` Thierry Volpiatto
2022-09-29 16:34 ` Stefan Kangas
2022-09-29 14:16 ` master fe7c015b20: Support XFCE in wallpaper.el Stefan Kangas
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