bug#28587: 26.0.60; Don't write object name strings in object-write method

[Eric Abrahamsen <eric@ericabrahamsen.net>]

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On 10/21/17 23:29 PM, Stefan Monnier wrote:

[...]

> This is more problematic since data generated with this hunk will be
> incompatible with an Emacs which doesn't have the other hunk applied.
> So I think this should be conditional on a defcustom and by default this
> defcustom should cause the code to still behave as before.

So where we're at now is, the previous chunk has gone into both master
and emacs-26. The next patch (below) would only go into master, so as to
be more conservative about what's emitted. Everything defaults to
current behavior.

This patch does two things: permits omission of the object name strings,
and permits shutting off indentation (which helps a lot for shrinking
the file size). In a previous version I had `eieio-print-depth' do
double duty as a boolean and an integer; this version has a separate
defvar for controlling whether indentation is printed at all.
`eieio-print-depth' still gets incremented; someone might find that
useful.

Eric


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From b75d0469dc986a73cbac6351537c30e535ce2890 Mon Sep 17 00:00:00 2001
From: Eric Abrahamsen <eric@ericabrahamsen.net>
Date: Wed, 8 Nov 2017 11:58:31 -0800
Subject: [PATCH] Provide more control over writing of objects in object-write

* lisp/emacs-lisp/eieio.el (eieio-print-indentation,
  eieio-print-object-name): New variables controlling whether an
  object name is printed for each object, and whether an object's
  contents are indented or not. Object names are obsoleted; omitting
  indentation reduces the size of persistence files.
---
 lisp/emacs-lisp/eieio.el | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/lisp/emacs-lisp/eieio.el b/lisp/emacs-lisp/eieio.el
index ca91c5a871..e07392d8c9 100644
--- a/lisp/emacs-lisp/eieio.el
+++ b/lisp/emacs-lisp/eieio.el
@@ -847,7 +847,17 @@ 'constructor
   (princ (object-print object) stream))
 
 (defvar eieio-print-depth 0
-  "When printing, keep track of the current indentation depth.")
+  "The current indentation depth while printing.
+Ignored if `eieio-print-indentation' is nil.")
+
+(defvar eieio-print-indentation t
+  "When non-nil, indent contents of printed objects.")
+
+(defvar eieio-print-object-name t
+  "When non-nil write the object name in `object-write'.
+Does not affect objects subclassing `eieio-named'.  Writing
+object names is deprecated as of Emacs 24.4; consider setting
+this to nil.")
 
 (cl-defgeneric object-write (this &optional comment)
   "Write out object THIS to the current stream.
@@ -860,9 +870,10 @@ eieio-print-depth
   If optional COMMENT is non-nil, include comments when outputting
 this object."
   (when comment
-    (princ ";; Object ")
-    (princ (eieio-object-name-string this))
-    (princ "\n")
+    (when eieio-print-object-name
+      (princ ";; Object ")
+      (princ (eieio-object-name-string this))
+      (princ "\n"))
     (princ comment)
     (princ "\n"))
   (let* ((cl (eieio-object-class this))
@@ -871,11 +882,13 @@ eieio-print-depth
     ;; It should look like this:
     ;; (<constructor> <name> <slot> <slot> ... )
     ;; Each slot's slot is writen using its :writer.
-    (princ (make-string (* eieio-print-depth 2) ? ))
+    (when eieio-print-indentation
+      (princ (make-string (* eieio-print-depth 2) ? )))
     (princ "(")
     (princ (symbol-name (eieio--class-constructor (eieio-object-class this))))
-    (princ " ")
-    (prin1 (eieio-object-name-string this))
+    (when eieio-print-object-name
+      (princ " ")
+      (prin1 (eieio-object-name-string this)))
     (princ "\n")
     ;; Loop over all the public slots
     (let ((slots (eieio--class-slots cv))
@@ -889,7 +902,8 @@ eieio-print-depth
               (unless (or (not i) (equal v (cl--slot-descriptor-initform slot)))
                 (unless (bolp)
                   (princ "\n"))
-                (princ (make-string (* eieio-print-depth 2) ? ))
+                (when eieio-print-indentation
+                  (princ (make-string (* eieio-print-depth 2) ? )))
                 (princ (symbol-name i))
                 (if (alist-get :printer (cl--slot-descriptor-props slot))
                     ;; Use our public printer
@@ -904,7 +918,7 @@ eieio-print-depth
                              "\n" " "))
                   (eieio-override-prin1 v))))))))
     (princ ")")
-    (when (= eieio-print-depth 0)
+    (when (zerop eieio-print-depth)
       (princ "\n"))))
 
 (defun eieio-override-prin1 (thing)
@@ -923,14 +937,16 @@ eieio-list-prin1
       (progn
 	(princ "'")
 	(prin1 list))
-    (princ (make-string (* eieio-print-depth 2) ? ))
+    (when eieio-print-indentation
+      (princ (make-string (* eieio-print-depth 2) ? )))
     (princ "(list")
     (let ((eieio-print-depth (1+ eieio-print-depth)))
       (while list
 	(princ "\n")
 	(if (eieio-object-p (car list))
 	    (object-write (car list))
-	  (princ (make-string (* eieio-print-depth 2) ? ))
+          (when eieio-print-indentation
+	   (princ (make-string (* eieio-print-depth) ? )))
 	  (eieio-override-prin1 (car list)))
 	(setq list (cdr list))))
     (princ ")")))
-- 
2.15.0