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.

3 files changed, 14 insertions, 30 deletions

diff --git a/lisp/net/eww.el b/lisp/net/eww.el
index 2a70560ca7b..cf31d37f072 100644
--- a/lisp/net/eww.el
+++ b/lisp/net/eww.el
@@ -25,7 +25,6 @@
 ;;; Code:
 
 (require 'cl-lib)
-(require 'format-spec)
 (require 'shr)
 (require 'url)
 (require 'url-queue)
diff --git a/lisp/net/imap.el b/lisp/net/imap.el
index aa10f0291fd..a492dc8c798 100644
--- a/lisp/net/imap.el
+++ b/lisp/net/imap.el
@@ -136,7 +136,6 @@
 ;;; Code:
 
 (eval-when-compile (require 'cl-lib))
-(require 'format-spec)
 (require 'utf7)
 (require 'rfc2104)
 ;; Hmm... digest-md5 is not part of Emacs.
@@ -517,12 +516,9 @@ sure of changing the value of `foo'."
              (process-connection-type imap-process-connection-type)
              (process (start-process
                        name buffer shell-file-name shell-command-switch
-                       (format-spec
-                        cmd
-                        (format-spec-make
-                         ?s server
-                         ?p (number-to-string port)
-                         ?l imap-default-user))))
+                       (format-spec cmd `((?s . ,server)
+                                          (?p . ,(number-to-string port))
+                                          (?l . ,imap-default-user)))))
              response)
         (when process
           (with-current-buffer buffer
@@ -583,12 +579,9 @@ sure of changing the value of `foo'."
              (process-connection-type imap-process-connection-type)
              (process (start-process
                        name buffer shell-file-name shell-command-switch
-                       (format-spec
-                        cmd
-                        (format-spec-make
-                         ?s server
-                         ?p (number-to-string port)
-                         ?l imap-default-user))))
+                       (format-spec cmd `((?s . ,server)
+                                          (?p . ,(number-to-string port))
+                                          (?l . ,imap-default-user)))))
              response)
         (when process
           (with-current-buffer buffer
@@ -701,13 +694,10 @@ sure of changing the value of `foo'."
              (process-connection-type imap-process-connection-type)
              (process (start-process
                        name buffer shell-file-name shell-command-switch
-                       (format-spec
-                        cmd
-                        (format-spec-make
-                         ?s server
-                         ?g imap-shell-host
-                         ?p (number-to-string port)
-                         ?l imap-default-user)))))
+                       (format-spec cmd `((?s . ,server)
+                                          (?g . ,imap-shell-host)
+                                          (?p . ,(number-to-string port))
+                                          (?l . ,imap-default-user))))))
         (when process
           (while (and (memq (process-status process) '(open run))
                       (set-buffer buffer) ;; XXX "blue moon" nntp.el bug
diff --git a/lisp/net/network-stream.el b/lisp/net/network-stream.el
index 1d5cf382a84..1c371f59870 100644
--- a/lisp/net/network-stream.el
+++ b/lisp/net/network-stream.el
@@ -170,8 +170,8 @@ a greeting from the server.
 :nowait, if non-nil, says the connection should be made
 asynchronously, if possible.
 
-:shell-command is a format-spec string that can be used if :type
-is `shell'.  It has two specs, %s for host and %p for port
+:shell-command is a `format-spec' string that can be used if
+:type is `shell'.  It has two specs, %s for host and %p for port
 number.  Example: \"ssh gateway nc %s %p\".
 
 :tls-parameters is a list that should be supplied if you're
@@ -453,11 +453,7 @@ gnutls-boot (as returned by `gnutls-boot-parameters')."
                   (network-stream-command stream capability-command eo-capa)
                   'tls)))))))
 
-(declare-function format-spec "format-spec" (format spec))
-(declare-function format-spec-make "format-spec" (&rest pairs))
-
 (defun network-stream-open-shell (name buffer host service parameters)
-  (require 'format-spec)
   (let* ((capability-command (plist-get parameters :capability-command))
          (eoc                (plist-get parameters :end-of-command))
          (start (with-current-buffer buffer (point)))
@@ -467,9 +463,8 @@ gnutls-boot (as returned by `gnutls-boot-parameters')."
                                   shell-command-switch
                                   (format-spec
                                    (plist-get parameters :shell-command)
-                                   (format-spec-make
-                                    ?s host
-                                    ?p service))))))
+                                   `((?s . ,host)
+                                     (?p . ,service)))))))
     (when coding (if (consp coding)
                        (set-process-coding-system stream
                                                   (car coding)