Fix and extend format-spec (bug#41758)

* lisp/format-spec.el: Use lexical-binding.  Remove dependence on
subr-x.el.
(format-spec-make): Clarify docstring.
(format-spec--parse-modifiers): Rename to...
(format-spec--parse-flags): ...this and simplify.  In particular,
don't bother parsing :space-pad which is redundant and unused.
(format-spec--pad): Remove, replacing with...
(format-spec--do-flags): ...this new helper function which performs
more of format-spec's supported text manipulation.
(format-spec): Autoload.  Allow optional argument to take on special
values 'ignore' and 'delete' for more control over what happens when
a replacement for a format specification isn't provided.  Bring back
proper support for a precision modifier similar to that of 'format'.

* lisp/battery.el (battery-format): Rewrite in terms of format-spec.
(battery-echo-area-format, battery-mode-line-format): Mention
support of format-spec syntax in docstrings.

* doc/lispref/strings.texi (Custom Format Strings):
* etc/NEWS: Document and announce these changes.

* lisp/dired-aux.el (dired-do-compress-to):
* lisp/erc/erc-match.el (erc-log-matches):
* lisp/erc/erc.el (erc-update-mode-line-buffer):
* lisp/gnus/gnus-sieve.el (gnus-sieve-update):
* lisp/gnus/gssapi.el (open-gssapi-stream):
* lisp/gnus/mail-source.el (mail-source-fetch-file)
(mail-source-fetch-directory, mail-source-fetch-pop)
(mail-source-fetch-imap):
* lisp/gnus/message.el (message-insert-formatted-citation-line):
* lisp/image-dired.el:
* lisp/net/eww.el:
* lisp/net/imap.el (imap-kerberos4-open, imap-gssapi-open)
(imap-shell-open):
* lisp/net/network-stream.el (network-stream-open-shell):
* lisp/obsolete/tls.el (open-tls-stream):
* lisp/textmodes/tex-mode.el:
Remove extraneous loads and autoloads of format-spec now that it is
autoloaded and simplify its uses where possible.

* test/lisp/battery-tests.el (battery-format): Test new format-spec
support.
* test/lisp/format-spec-tests.el (test-format-spec): Rename to...
(format-spec) ...this, extending test cases.
(test-format-unknown): Rename to...
(format-spec-unknown): ...this, extending test cases.
(test-format-modifiers): Rename to...
(format-spec-flags): ...this.
(format-spec-make, format-spec-parse-flags, format-spec-do-flags)
(format-spec-do-flags-truncate, format-spec-do-flags-pad)
(format-spec-do-flags-chop, format-spec-do-flags-case): New tests.

2 files changed, 131 insertions, 8 deletions

diff --git a/test/lisp/battery-tests.el b/test/lisp/battery-tests.el
index 052ae49a800..4cb7470d884 100644
--- a/test/lisp/battery-tests.el
+++ b/test/lisp/battery-tests.el
@@ -52,7 +52,7 @@
   "Test `battery-format'."
   (should (equal (battery-format "" ()) ""))
   (should (equal (battery-format "" '((?b . "-"))) ""))
-  (should (equal (battery-format "%a%b%p%%" '((?b . "-") (?p . "99")))
-                 "-99%")))
+  (should (equal (battery-format "%2a%-3b%.1p%%" '((?b . "-") (?p . "99")))
+                 "-  9%")))
 
 ;;; battery-tests.el ends here
diff --git a/test/lisp/format-spec-tests.el b/test/lisp/format-spec-tests.el
index 23ee88c5269..11882217afb 100644
--- a/test/lisp/format-spec-tests.el
+++ b/test/lisp/format-spec-tests.el
@@ -22,22 +22,145 @@
 (require 'ert)
 (require 'format-spec)
 
-(ert-deftest test-format-spec ()
+(ert-deftest format-spec-make ()
+  "Test `format-spec-make'."
+  (should-not (format-spec-make))
+  (should-error (format-spec-make ?b))
+  (should (equal (format-spec-make ?b "b") '((?b . "b"))))
+  (should-error (format-spec-make ?b "b" ?a))
+  (should (equal (format-spec-make ?b "b" ?a 'a)
+                 '((?b . "b")
+                   (?a . a)))))
+
+(ert-deftest format-spec-parse-flags ()
+  "Test `format-spec--parse-flags'."
+  (should-not (format-spec--parse-flags nil))
+  (should-not (format-spec--parse-flags ""))
+  (should (equal (format-spec--parse-flags "-") '(:pad-right)))
+  (should (equal (format-spec--parse-flags " 0") '(:pad-zero)))
+  (should (equal (format-spec--parse-flags " -x0y< >^_z ")
+                 '(:pad-right :pad-zero :chop-left :chop-right
+                              :upcase :downcase))))
+
+(ert-deftest format-spec-do-flags ()
+  "Test `format-spec--do-flags'."
+  (should (equal (format-spec--do-flags "" () nil nil) ""))
+  (dolist (flag '(:pad-zero :pad-right :upcase :downcase
+                            :chop-left :chop-right))
+    (should (equal (format-spec--do-flags "" (list flag) nil nil) "")))
+  (should (equal (format-spec--do-flags "FOOBAR" '(:downcase :chop-right) 5 2)
+                 "   fo"))
+  (should (equal (format-spec--do-flags
+                  "foobar" '(:pad-zero :pad-right :upcase :chop-left) 5 2)
+                 "AR000")))
+
+(ert-deftest format-spec-do-flags-truncate ()
+  "Test `format-spec--do-flags' truncation."
+  (let (flags)
+    (should (equal (format-spec--do-flags "" flags nil 0) ""))
+    (should (equal (format-spec--do-flags "" flags nil 1) ""))
+    (should (equal (format-spec--do-flags "a" flags nil 0) ""))
+    (should (equal (format-spec--do-flags "a" flags nil 1) "a"))
+    (should (equal (format-spec--do-flags "a" flags nil 2) "a"))
+    (should (equal (format-spec--do-flags "asd" flags nil 0) ""))
+    (should (equal (format-spec--do-flags "asd" flags nil 1) "a")))
+  (let ((flags '(:chop-left)))
+    (should (equal (format-spec--do-flags "" flags nil 0) ""))
+    (should (equal (format-spec--do-flags "" flags nil 1) ""))
+    (should (equal (format-spec--do-flags "a" flags nil 0) ""))
+    (should (equal (format-spec--do-flags "a" flags nil 1) "a"))
+    (should (equal (format-spec--do-flags "a" flags nil 2) "a"))
+    (should (equal (format-spec--do-flags "asd" flags nil 0) ""))
+    (should (equal (format-spec--do-flags "asd" flags nil 1) "d"))))
+
+(ert-deftest format-spec-do-flags-pad ()
+  "Test `format-spec--do-flags' padding."
+  (let (flags)
+    (should (equal (format-spec--do-flags "" flags 0 nil) ""))
+    (should (equal (format-spec--do-flags "" flags 1 nil) " "))
+    (should (equal (format-spec--do-flags "a" flags 0 nil) "a"))
+    (should (equal (format-spec--do-flags "a" flags 1 nil) "a"))
+    (should (equal (format-spec--do-flags "a" flags 2 nil) " a")))
+  (let ((flags '(:pad-zero)))
+    (should (equal (format-spec--do-flags "" flags 0 nil) ""))
+    (should (equal (format-spec--do-flags "" flags 1 nil) "0"))
+    (should (equal (format-spec--do-flags "a" flags 0 nil) "a"))
+    (should (equal (format-spec--do-flags "a" flags 1 nil) "a"))
+    (should (equal (format-spec--do-flags "a" flags 2 nil) "0a")))
+  (let ((flags '(:pad-right)))
+    (should (equal (format-spec--do-flags "" flags 0 nil) ""))
+    (should (equal (format-spec--do-flags "" flags 1 nil) " "))
+    (should (equal (format-spec--do-flags "a" flags 0 nil) "a"))
+    (should (equal (format-spec--do-flags "a" flags 1 nil) "a"))
+    (should (equal (format-spec--do-flags "a" flags 2 nil) "a ")))
+  (let ((flags '(:pad-right :pad-zero)))
+    (should (equal (format-spec--do-flags "" flags 0 nil) ""))
+    (should (equal (format-spec--do-flags "" flags 1 nil) "0"))
+    (should (equal (format-spec--do-flags "a" flags 0 nil) "a"))
+    (should (equal (format-spec--do-flags "a" flags 1 nil) "a"))
+    (should (equal (format-spec--do-flags "a" flags 2 nil) "a0"))))
+
+(ert-deftest format-spec-do-flags-chop ()
+  "Test `format-spec--do-flags' chopping."
+  (let ((flags '(:chop-left)))
+    (should (equal (format-spec--do-flags "a" flags 0 nil) ""))
+    (should (equal (format-spec--do-flags "a" flags 1 nil) "a"))
+    (should (equal (format-spec--do-flags "asd" flags 0 nil) ""))
+    (should (equal (format-spec--do-flags "asd" flags 1 nil) "d")))
+  (let ((flags '(:chop-right)))
+    (should (equal (format-spec--do-flags "a" flags 0 nil) ""))
+    (should (equal (format-spec--do-flags "a" flags 1 nil) "a"))
+    (should (equal (format-spec--do-flags "asd" flags 0 nil) ""))
+    (should (equal (format-spec--do-flags "asd" flags 1 nil) "a"))))
+
+(ert-deftest format-spec-do-flags-case ()
+  "Test `format-spec--do-flags' case fiddling."
+  (dolist (flag '(:pad-zero :pad-right :chop-left :chop-right))
+    (let ((flags (list flag)))
+      (should (equal (format-spec--do-flags "a" flags nil nil) "a"))
+      (should (equal (format-spec--do-flags "A" flags nil nil) "A")))
+    (let ((flags (list flag :downcase)))
+      (should (equal (format-spec--do-flags "a" flags nil nil) "a"))
+      (should (equal (format-spec--do-flags "A" flags nil nil) "a")))
+    (let ((flags (list flag :upcase)))
+      (should (equal (format-spec--do-flags "a" flags nil nil) "A"))
+      (should (equal (format-spec--do-flags "A" flags nil nil) "A")))))
+
+(ert-deftest format-spec ()
+  (should (equal (format-spec "" ()) ""))
+  (should (equal (format-spec "a" ()) "a"))
+  (should (equal (format-spec "b" '((?b . "bar"))) "b"))
+  (should (equal (format-spec "%%%b%%b%b%%" '((?b . "bar"))) "%bar%bbar%"))
   (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")))
+                 "foo        bar zot"))
+  (should (equal-including-properties
+           (format-spec (propertize "a" 'a 'b) '((?a . "foo")))
+           #("a" 0 1 (a b))))
+  (let ((fmt (concat (propertize "%a" 'a 'b)
+                     (propertize "%%" 'c 'd)
+                     "%b"
+                     (propertize "%b" 'e 'f))))
+    (should (equal-including-properties
+             (format-spec fmt '((?b . "asd") (?a . "fgh")))
+             #("fgh%asdasd" 0 3 (a b) 3 4 (c d) 7 10 (e f))))))
 
-(ert-deftest test-format-unknown ()
+(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"))))
   (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")))
+  (should (equal (format-spec "foo %4b %%%4z %%4 zot" '((?b . "bar")) t)
+                 "foo  bar %%%4z %%4 zot"))
+  (should (equal (format-spec "foo %4b %%%4z %%4 zot" '((?b . "bar")) 'ignore)
+                 "foo  bar %%4z %4 zot"))
+  (should (equal (format-spec "foo %4b %%%4z %%4 zot" '((?b . "bar")) 'delete)
+                 "foo  bar % %4 zot")))
 
-(ert-deftest test-format-modifiers ()
+(ert-deftest format-spec-flags ()
   (should (equal (format-spec "foo %10b zot" '((?b . "bar")))
                  "foo        bar zot"))
   (should (equal (format-spec "foo % 10b zot" '((?b . "bar")))