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.

7 files changed, 160 insertions, 104 deletions

diff --git a/admin/unidata/unidata-gen.el b/admin/unidata/unidata-gen.el
index 149f7535588..dc8c071999e 100644
--- a/admin/unidata/unidata-gen.el
+++ b/admin/unidata/unidata-gen.el
@@ -89,6 +89,7 @@
 ;; PROPn: string representing the nth property value
 
 (eval-when-compile (require 'cl-lib))
+(require 'generate-file)
 
 (defvar unidata-list nil)
 
@@ -1422,13 +1423,14 @@ Property value is a symbol `o' (Open), `c' (Close), or `n' (None)."
       (or elt (user-error "Unknown output file: %s" basename))
       (or noninteractive (message "Generating %s..." file))
       (with-temp-file file
-        (insert ";;; " basename "  -*- lexical-binding:t -*-
-;; " copyright "
-;; Generated from Unicode data files by unidata-gen.el.
-;; The sources for this file are found in the admin/unidata/ directory in
-;; the Emacs sources.  The Unicode data files are used under the
-;; Unicode Terms of Use, as contained in the file copyright.html in that
-;; same directory.\n")
+        (generate-file-heading
+         basename
+         :text (concat copyright "  \
+Generated from Unicode data files by unidata-gen.el. \
+The sources for this file are found in the admin/unidata/ directory in \
+the Emacs sources.  The Unicode data files are used under the \
+Unicode Terms of Use, as contained in the file copyright.html in that \
+same directory."))
         (dolist (proplist (cdr elt))
           (let ((prop (unidata-prop-prop proplist))
                 (index (unidata-prop-index proplist))
@@ -1446,21 +1448,15 @@ Property value is a symbol `o' (Open), `c' (Close), or `n' (None)."
               (set-char-table-extra-slot table 3 describer))
             (insert (format "(define-char-code-property '%S\n  %S\n  %S)\n"
                             prop table docstring))))
-        (insert ";; Local Variables:\n"
-                ";; coding: utf-8\n"
-                ";; version-control: never\n"
-                ";; no-byte-compile: t\n"
-                ";; no-update-autoloads: t\n"
-                ";; End:\n\n"
-                (format ";;; %s ends here\n" basename)))))
+        (generate-file-trailer basename :inhibit-provide t))))
   (or noninteractive (message "Generating %s...done" file)))
 
 (defun unidata-gen-charprop (&optional charprop-file text)
   (or charprop-file (setq charprop-file (pop command-line-args-left)))
   (with-temp-file charprop-file
-    (insert ";; Automatically generated by unidata-gen.el."
-            "  -*- lexical-binding: t -*-\n"
-            ";; See the admin/unidata/ directory in the Emacs sources.\n")
+    (generate-file-heading
+     charprop-file
+     :text "Automatically generated by unidata-gen.el.  See the admin/unidata/ directory in the Emacs sources.")
     (if text
         (insert text)
       (dolist (elt unidata-file-alist)
@@ -1469,19 +1465,7 @@ Property value is a symbol `o' (Open), `c' (Close), or `n' (None)."
                           (unidata-prop-prop proplist) (car elt)
                           (unidata-prop-docstring proplist))))))
     (or noninteractive (message "Writing %s..." charprop-file))
-    (insert "\n"
-            (format "(provide '%s)\n"
-                    (file-name-sans-extension
-                     (file-name-nondirectory charprop-file)))
-            "\n"
-            ";; Local Variables:\n"
-            ";; coding: utf-8\n"
-            ";; version-control: never\n"
-            ";; no-byte-compile: t\n"
-            ";; no-update-autoloads: t\n"
-            ";; End:\n\n"
-            (format ";;; %s ends here\n"
-                    (file-name-nondirectory charprop-file)))))
+    (generate-file-trailer charprop-file)))
 
 (defun unidata-gen-scripts (&optional file)
   ;; Running from Makefile.
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)
diff --git a/lisp/international/emoji.el b/lisp/international/emoji.el
index df488708afa..d53b01173d5 100644
--- a/lisp/international/emoji.el
+++ b/lisp/international/emoji.el
@@ -31,6 +31,7 @@
 (require 'cl-extra)
 (require 'transient)
 (require 'multisession)
+(require 'generate-file)
 
 (defgroup emoji nil
   "Inserting Emojis."
@@ -415,8 +416,8 @@ the name is not known."
     (dolist (glyph glyphs)
       (remhash glyph emoji--derived)))
   (with-temp-buffer
-    (insert ";; Generated file -- do not edit.   -*- lexical-binding:t -*-
-;; Copyright © 1991-2021 Unicode, Inc.
+    (generate-file-heading file)
+    (insert ";; Copyright © 1991-2021 Unicode, Inc.
 ;; Generated from Unicode data files by emoji.el.
 ;; The source for this file is found in the admin/unidata/emoji-test.txt
 ;; file in the Emacs sources.  The Unicode data files are used under the
@@ -426,18 +427,7 @@ the name is not known."
       (insert (format "(defconst %s '" var))
       (pp (symbol-value var) (current-buffer))
       (insert (format "\n) ;; End %s\n\n" var)))
-    (insert ";; Local" " Variables:
-;; coding: utf-8
-;; version-control: never
-;; no-byte-"
-            ;; Obfuscate to not inhibit compilation of this file, too.
-            "compile: t
-;; no-update-autoloads: t
-;; End:
-
-\(provide 'emoji-labels)
-
-\;;; emoji-labels.el ends here\n")
+    (generate-file-trailer file)
     (write-region (point-min) (point-max) file)))
 
 (defun emoji--base-name (name derivations)
diff --git a/lisp/international/ja-dic-cnv.el b/lisp/international/ja-dic-cnv.el
index 7f7c0261dca..563eba6682b 100644
--- a/lisp/international/ja-dic-cnv.el
+++ b/lisp/international/ja-dic-cnv.el
@@ -44,6 +44,8 @@
 
 ;;; Code:
 
+(require 'generate-file)
+
 ;; Name of a file to generate from SKK dictionary.
 (defvar ja-dic-filename "ja-dic.el")
 
@@ -340,13 +342,11 @@ Saves the output as `ja-dic-filename', in directory DIRNAME (if specified)."
     (with-current-buffer buf
       (erase-buffer)
       (buffer-disable-undo)
-      (insert ";;; ja-dic.el --- dictionary for Japanese input method"
-              "  -*- lexical-binding:t -*-\n"
-              ";;\tGenerated by the command `skkdic-convert'\n"
+      (generate-file-heading ja-dic-filename :code nil)
+      (insert ";;\tGenerated by the `skkdic-convert' function.\n"
               ";;\tOriginal SKK dictionary file: "
               (file-relative-name (expand-file-name filename) dirname)
               "\n\n"
-              ";; This file is part of GNU Emacs.\n\n"
               ";;; Start of the header of the original SKK dictionary.\n\n")
       (set-buffer skkbuf)
       (goto-char 1)
@@ -394,13 +394,7 @@ Saves the output as `ja-dic-filename', in directory DIRNAME (if specified)."
         ;; Postfix
         (with-current-buffer buf
           (goto-char (point-max))
-          (insert ";;\n(provide 'ja-dic)\n\n"
-                  ";; Local Variables:\n"
-                  ";; version-control: never\n"
-                  ";; no-update-autoloads: t\n"
-                  ";; coding: utf-8\n"
-                  ";; End:\n\n"
-                  ";;; ja-dic.el ends here\n")))
+          (generate-file-trailer ja-dic-filename :compile t)))
 
       ;; Save the working buffer.
       (set-buffer buf)
diff --git a/lisp/international/titdic-cnv.el b/lisp/international/titdic-cnv.el
index a3b62667915..bdb77ca7026 100644
--- a/lisp/international/titdic-cnv.el
+++ b/lisp/international/titdic-cnv.el
@@ -62,6 +62,7 @@
 ;;; Code:
 
 (require 'quail)
+(require 'generate-file)
 
 ;; List of values of key "ENCODE:" and the corresponding Emacs
 ;; coding-system and language environment name.
@@ -269,13 +270,12 @@ SPC, 6, 3, 4, or 7 specifying a tone (SPC:陰平, 6:陽平, 3:上聲, 4:去聲,
         (tit-moveleft ",<")
         (tit-keyprompt nil))
 
-    (princ (format ";;; %s  -*- lexical-binding:t -*-\n"
-                   (file-name-nondirectory filename)))
+    (generate-file-heading filename :code nil)
     (princ ";; Quail package `")
     (princ package)
     (princ "\n")
     (princ (substitute-command-keys
-            ";;   Generated by the command `titdic-convert'\n"))
+            ";;   Generated by the `titdic-convert' function.\n"))
     (princ ";;\tOriginal TIT dictionary file: ")
     (princ (file-name-nondirectory filename))
     (princ "\n\n")
@@ -521,11 +521,8 @@ the generated Quail package is saved."
 
           ;; Process the body part
           (tit-process-body)
-
-          (princ ";; Local Variables:\n")
-          (princ ";; version-control: never\n")
-          (princ ";; no-update-autoloads: t\n")
-          (princ ";; End:\n"))))))
+          (generate-file-trailer
+           filename :inhibit-provide t :compile t :coding nil))))))
 
 ;;;###autoload
 (defun batch-titdic-convert (&optional force)
@@ -1135,11 +1132,10 @@ the generated Quail package is saved."
         ;; Explicitly set eol format to `unix'.
         (setq coding-system-for-write 'utf-8-unix)
         (with-temp-file (expand-file-name quailfile dirname)
-          (insert (format ";;; %s  -*- lexical-binding:t -*-\n"
-                          (file-name-nondirectory quailfile)))
+          (generate-file-heading quailfile)
           (insert (format-message ";; Quail package `%s'\n" name))
           (insert (format-message
-                   ";;   Generated by the command `miscdic-convert'\n"))
+                   ";;   Generated by the `miscdic-convert' function.\n"))
           (insert ";;   Source dictionary file: " dicfile "\n")
           (insert ";;   Copyright notice of the source file\n")
           (insert ";;------------------------------------------------------\n")
@@ -1161,11 +1157,8 @@ the generated Quail package is saved."
               (let ((dicbuf (current-buffer)))
                 (with-current-buffer dstbuf
                   (funcall converter dicbuf)))))
-          (insert ";; Local Variables:\n"
-                  ";; version-control: never\n"
-                  ";; no-update-autoloads: t\n"
-                  ";; End:\n\n"
-                  ";;; " quailfile " ends here\n")))
+          (generate-file-trailer
+           quailfile :inhibit-provide t :compile t :coding nil)))
       (setq tail (cdr tail)))))
 
 (defun batch-miscdic-convert ()
@@ -1228,7 +1221,4 @@ The library is named pinyin.el, and contains the constant
       (insert "(provide 'pinyin)\n"))
     (kill-emacs 0)))
 
-;; Prevent "Local Variables" above confusing Emacs.
-
-
 ;;; titdic-cnv.el ends here
diff --git a/lisp/url/url-cookie.el b/lisp/url/url-cookie.el
index 42e1fa22fac..dab367485e9 100644
--- a/lisp/url/url-cookie.el
+++ b/lisp/url/url-cookie.el
@@ -26,6 +26,7 @@
 (require 'url-util)
 (require 'url-parse)
 (require 'url-domsuf)
+(require 'generate-file)
 
 (eval-when-compile (require 'cl-lib))
 
@@ -158,10 +159,7 @@ i.e. 1970-1-1) are loaded as expiring one year from now instead."
         (insert ")\n(setq url-cookie-secure-storage\n '")
         (pp url-cookie-secure-storage (current-buffer)))
       (insert ")\n")
-      (insert "\n;; Local Variables:\n"
-              ";; version-control: never\n"
-              ";; no-byte-compile: t\n"
-              ";; End:\n")
+      (generate-file-trailer fname :inhibit-provide t :autoloads t)
       (setq-local version-control 'never)
       (write-file fname))
     (setq url-cookies-changed-since-last-save nil))))