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Allow passing unknown specs to format-spec

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* lisp/format-spec.el (format-spec): Allow passing through format
strings that have no specs (to be able to act as a filter).  Also
add an example.
* test/lisp/format-spec-tests.el (test-format-spec): Add tests for
the new functionality.
This commit is contained in:
Lars Ingebrigtsen 2019-07-11 18:44:30 +02:00
parent b41ddb7a8b
commit b44f0c4579
2 changed files with 53 additions and 28 deletions
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69
lisp/format-spec.el
View file

@ -24,40 +24,55 @@
;;; Code:
(defun format-spec (format specification)
(defun format-spec (format specification &optional only-present)
"Return a string based on FORMAT and SPECIFICATION.
FORMAT is a string containing `format'-like specs like \"bash %u %k\",
FORMAT is a string containing `format'-like specs like \"su - %u %k\",
while SPECIFICATION is an alist mapping from format spec characters
to values. Any text properties on a %-spec itself are propagated to
the text that it generates."
to values.
For instance:
(format-spec \"su - %u %k\"
`((?u . ,(user-login-name))
(?k . \"ls\")))
Any text properties on a %-spec itself are propagated to the text
that it generates.
If ONLY-PRESENT, format spec characters not present in
SPECIFICATION are ignored, and the \"%\" characters are left
where they are, including \"%%\" strings."
(with-temp-buffer
(insert format)
(goto-char (point-min))
(while (search-forward "%" nil t)
(cond
;; Quoted percent sign.
((eq (char-after) ?%)
(delete-char 1))
;; Valid format spec.
((looking-at "\\([-0-9.]*\\)\\([a-zA-Z]\\)")
(let* ((num (match-string 1))
(spec (string-to-char (match-string 2)))
(val (assq spec specification)))
(unless val
(error "Invalid format character: `%%%c'" spec))
(setq val (cdr val))
;; Pad result to desired length.
(let ((text (format (concat "%" num "s") val)))
;; Insert first, to preserve text properties.
(insert-and-inherit text)
;; Delete the specifier body.
(delete-region (+ (match-beginning 0) (length text))
(+ (match-end 0) (length text)))
;; Delete the percent sign.
(delete-region (1- (match-beginning 0)) (match-beginning 0)))))
;; Signal an error on bogus format strings.
(t
(error "Invalid format string"))))
;; Quoted percent sign.
((eq (char-after) ?%)
(unless only-present
(delete-char 1)))
;; Valid format spec.
((looking-at "\\([-0-9.]*\\)\\([a-zA-Z]\\)")
(let* ((num (match-string 1))
(spec (string-to-char (match-string 2)))
(val (assq spec specification)))
(if (not val)
(unless only-present
(error "Invalid format character: `%%%c'" spec))
(setq val (cdr val))
;; Pad result to desired length.
(let ((text (format (concat "%" num "s") val)))
;; Insert first, to preserve text properties.
(insert-and-inherit text)
;; Delete the specifier body.
(delete-region (+ (match-beginning 0) (length text))
(+ (match-end 0) (length text)))
;; Delete the percent sign.
(delete-region (1- (match-beginning 0)) (match-beginning 0))))))
;; Signal an error on bogus format strings.
(t
(unless only-present
(error "Invalid format string")))))
(buffer-string)))
(defun format-spec-make (&rest pairs)

12
test/lisp/format-spec-tests.el
View file

@ -23,11 +23,21 @@
(require 'format-spec)
(ert-deftest test-format-spec ()
(should (equal (format-spec "foo %b zot" '((?b . "bar")))
(should (equal (format-spec "foo %b zot" `((?b . "bar")))
"foo bar zot"))
(should (equal (format-spec "foo %-10b zot" '((?b . "bar")))
"foo bar zot"))
(should (equal (format-spec "foo %10b zot" '((?b . "bar")))
"foo bar zot")))
(ert-deftest test-format-unknown ()
(should (eq (condition-case _
(format-spec "foo %b %z zot" '((?b . "bar")))
(error :error))
:error))
(should (equal (format-spec "foo %b %z zot" '((?b . "bar")) t)
"foo bar %z zot"))
(should (equal (format-spec "foo %b %z %% zot" '((?b . "bar")) t)
"foo bar %z %% zot")))
;;; format-spec-tests.el ends here