Add convenience functions for generating Emacs Lisp files

* lisp/url/url-cookie.el (url-cookie-write-file):
* lisp/international/titdic-cnv.el (tit-process-header):
* lisp/international/ja-dic-cnv.el (skkdic-convert):
* lisp/international/emoji.el (emoji--generate-file):
* lisp/emacs-lisp/loaddefs-gen.el (loaddefs-generate--rubric)

* admin/unidata/unidata-gen.el (unidata-gen-file)
(unidata-gen-charprop): Use the new functions.

* lisp/emacs-lisp/generate-file.el: New file to provide
convenience functions for generated files.  It's not always
trivial to know which parts of the trailer that has to be
obfuscated to avoid not getting byte-compiled etc, and some parts
of the headers/trailers are usually forgotten when hand-coding
these.

2 files changed, 126 insertions, 26 deletions

diff --git a/lisp/emacs-lisp/generate-file.el b/lisp/emacs-lisp/generate-file.el
new file mode 100644
index 00000000000..456503df6a3
--- /dev/null
+++ b/lisp/emacs-lisp/generate-file.el
@@ -0,0 +1,111 @@
+;;; generate-file.el --- utility functions for generated files  -*- lexical-binding: t -*-
+
+;; Copyright (C) 2022 Free Software Foundation, Inc.
+
+;; Keywords: maint
+;; Package: emacs
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+(eval-when-compile (require 'cl-lib))
+
+(cl-defun generate-file-heading (file &key description text (code t))
+  "Insert a standard header for FILE.
+This header will specify that this is a generated file that
+should not be edited.
+
+If `standard-output' is bound to a buffer, insert in that buffer.
+If no, insert at point in the current buffer.
+
+DESCRIPTION (if any) will be used in the first line.
+
+TEXT (if given) will be inserted as a comment.
+
+If CODE is non-nil (which is the default), a Code: line is
+inserted."
+  (with-current-buffer (if (bufferp standard-output)
+                           standard-output
+                         (current-buffer))
+    (insert ";;; " (file-name-nondirectory file)
+            " --- "
+            (or description "automatically generated")
+            " (do not edit) "
+            "  -*- lexical-binding: t -*-\n\n"
+            ";; This file is part of GNU Emacs.\n\n")
+    (when text
+      (insert ";;; Commentary:\n\n")
+      (let ((start (point))
+            (fill-prefix ";; "))
+        (insert ";; " text)
+        (fill-region start (point))))
+    (ensure-empty-lines 1)
+    (when code
+      (insert ";;; Code:\n\n"))))
+
+(cl-defun generate-file-trailer (file &key version inhibit-provide
+                                      (coding 'utf-8-emacs-unix) autoloads
+                                      compile provide)
+  "Insert a standard trailer for FILE.
+By default, this trailer inhibits version control, byte
+compilation, updating autoloads, and uses a `utf-8-emacs-unix'
+coding system.  These can be inhibited by providing non-nil
+values to the VERSION, NO-PROVIDE, AUTOLOADS and COMPILE
+keyword arguments.
+
+CODING defaults to `utf-8-emacs-unix'.  Use a nil value to
+inhibit generating this setting, or a coding system value to use
+that.
+
+If PROVIDE is non-nil, use that in the `provide' statement
+instead of using FILE as the basis.
+
+If `standard-output' is bound to a buffer, insert in that buffer.
+If no, insert at point in the current buffer."
+  (with-current-buffer (if (bufferp standard-output)
+                           standard-output
+                         (current-buffer))
+    (ensure-empty-lines 1)
+    (unless inhibit-provide
+      (insert (format "(provide '%s)\n\n"
+                      (or provide
+	                  (file-name-sans-extension
+                           (file-name-nondirectory file))))))
+    ;; Some of the strings below are chopped into bits to inhibit
+    ;; automatic scanning tools from thinking that they are actual
+    ;; directives.
+    (insert ";; Local " "Variables:\n")
+    (unless version
+      (insert ";; version-control: never\n"))
+    (unless compile
+      (insert ";; no-byte-" "compile: t\n")) ;; #$ is byte-compiled into nil.
+    (unless autoloads
+      (insert ";; no-update-autoloads: t\n"))
+    (when coding
+      (insert (format ";; coding: %s\n"
+                      (if (eq coding t)
+                          'utf-8-emacs-unix
+                        coding))))
+    (insert
+     ";; End:\n\n"
+     ";;; " (file-name-nondirectory file) " ends here\n")))
+
+(provide 'generate-file)
+
+;;; generate-file.el ends here
diff --git a/lisp/emacs-lisp/loaddefs-gen.el b/lisp/emacs-lisp/loaddefs-gen.el
index dce5466be2d..9aa2967d7b3 100644
--- a/lisp/emacs-lisp/loaddefs-gen.el
+++ b/lisp/emacs-lisp/loaddefs-gen.el
@@ -40,6 +40,7 @@
 
 (require 'radix-tree)
 (require 'lisp-mnt)
+(require 'generate-file)
 
 (defvar autoload-compute-prefixes t
   "If non-nil, autoload will add code to register the prefixes used in a file.
@@ -437,32 +438,20 @@ but adds an extra line to the output to modify `load-path'.
 If FEATURE is non-nil, FILE will provide a feature.  FEATURE may
 be a string naming the feature, otherwise it will be based on
 FILE's name."
-  (let ((basename (file-name-nondirectory file))
-	(lp (if (equal type "package") (setq type "autoloads"))))
-    (concat ";;; " basename
-            " --- automatically extracted " (or type "autoloads")
-            "  -*- lexical-binding: t -*-\n"
-            (when (string-match "/lisp/loaddefs\\.el\\'" file)
-              ";; This file will be copied to ldefs-boot.el and checked in periodically.\n")
-	    ";;\n"
-	    ";;; Code:\n\n"
-	    (if lp
-		"(add-to-list 'load-path (directory-file-name
-                         (or (file-name-directory #$) (car load-path))))\n\n")
-	    "\n;;; End of scraped data\n\n"
-	    ;; This is used outside of autoload.el, eg cus-dep, finder.
-	    (if feature
-		(format "(provide '%s)\n"
-			(if (stringp feature) feature
-			  (file-name-sans-extension basename))))
-	    ";; Local Variables:\n"
-	    ";; version-control: never\n"
-            ";; no-byte-compile: t\n" ;; #$ is byte-compiled into nil.
-	    ";; no-update-autoloads: t\n"
-	    ";; coding: utf-8-emacs-unix\n"
-	    ";; End:\n"
-	    ";;; " basename
-	    " ends here\n")))
+  (let ((lp (and (equal type "package") (setq type "autoloads"))))
+    (with-temp-buffer
+      (generate-file-heading
+       file
+       :description (concat "automatically extracted " (or type "autoloads"))
+       :text (and (string-match "/lisp/loaddefs\\.el\\'" file)
+                  "This file will be copied to ldefs-boot.el and checked in periodically."))
+      (when lp
+        (insert "(add-to-list 'load-path (directory-file-name
+                         (or (file-name-directory #$) (car load-path))))\n\n"))
+      (insert "\n;;; End of scraped data\n\n")
+      (generate-file-trailer file :provide (and (stringp feature) feature)
+                             :inhibit-provide (not feature))
+      (buffer-string))))
 
 (defun loaddefs-generate--insert-section-header (outbuf autoloads
                                                         load-name file time)