bug#29923: [PATCH] Skip writing empty abbrev tables

[Allen Li <darkfeline@felesatra.moe>]

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Attached new patch

On Wed, Sep 19, 2018 at 6:44 AM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Allen Li <darkfeline@felesatra.moe>
> > Date: Tue, 18 Sep 2018 19:55:38 -0700
> > Cc: Allen Li <vianchielfaura@gmail.com>, 29923@debbugs.gnu.org
> >
> > > Ah, it would be good to have this information in the commit message, as
> > > the patch is a bit confusing to read otherwise.
> >
> > Done.  I have also removed the system abbrev check in abbrev--write since
> > it is redundant now and this is the only place it is called.
>
> I think this change in behavior warrants a NEWS entry, and I think the
> description in the ELisp manual should also be updated.
>
> > To implement this, we need to filter out out system abbrevs before
>                                        ^^^^^^^
> A typo.

Done

>
> Thanks.

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From 1510152169b6cc8b5cb1d0daa59578cec1373f13 Mon Sep 17 00:00:00 2001
From: Allen Li <darkfeline@felesatra.moe>
Date: Sun, 31 Dec 2017 20:33:21 -0800
Subject: [PATCH] Skip writing empty abbrev tables

Fixes bug#29923

insert-abbrev-table-description with a non-nil READABLE inserts Lisp
forms suitable for evaluation to restore the defined abbrevs.  We
don't have to insert a form for tables that do not have any abbrevs.

To implement this, we need to filter out system abbrevs before
checking if a table is empty, because system abbrevs were previously
skipped in the abbrev--write call, at which point we would already
have started inserting the beginning of a table definition form.

* lisp/abbrev.el (insert-abbrev-table-description):
Skip inserting empty tables when READABLE is non-nil.
Clarify behavior in documentation string.
* lisp/abbrev.el (abbrev--write): Remove system abbrev check.
---
 doc/lispref/abbrevs.texi | 16 ++++----
 etc/NEWS                 |  6 +++
 lisp/abbrev.el           | 85 +++++++++++++++++++++-------------------
 3 files changed, 60 insertions(+), 47 deletions(-)

diff --git a/doc/lispref/abbrevs.texi b/doc/lispref/abbrevs.texi
index 087e694520..32d1d8d036 100644
--- a/doc/lispref/abbrevs.texi
+++ b/doc/lispref/abbrevs.texi
@@ -112,17 +112,19 @@ Abbrev Tables
 @code{define-abbrev-table} adds the new abbrev table name to this list.
 @end defvar
 
-@defun insert-abbrev-table-description name &optional human
+@defun insert-abbrev-table-description name &optional readable
 This function inserts before point a description of the abbrev table
 named @var{name}.  The argument @var{name} is a symbol whose value is an
 abbrev table.  @c The return value is always @code{nil}.
 
-If @var{human} is non-@code{nil}, the description is human-oriented.
-System abbrevs are listed and identified as such.  Otherwise the
-description is a Lisp expression---a call to @code{define-abbrev-table}
-that would define @var{name} as it is currently defined, but without
-the system abbrevs.  (The mode or package using @var{name} is supposed
-to add these to @var{name} separately.)
+If @var{readable} is non-@code{nil}, the description is
+human-oriented.  System abbrevs are listed and identified as such.
+Otherwise the description is a Lisp expression, a call to
+@code{define-abbrev-table}, that would define @var{name} as it is
+currently defined, but without the system abbrevs (the mode or package
+using @var{name} is supposed to add these to @var{name} separately).
+However, if the resulting expression would not define any abbrevs,
+nothing is inserted.
 @end defun
 
 @node Defining Abbrevs
diff --git a/etc/NEWS b/etc/NEWS
index bc6791b05b..9032f90643 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -246,6 +246,12 @@ case does not match.
 'write-abbrev-file' now writes special properties like ':case-fixed'
 for abbrevs that have them.
 
++++
+** 'insert-abbrev-table-description' skips empty tables.
+'insert-abbrev-table-description' skips inserting empty tables when
+inserting non-readable tables.  By extension, this makes
+'write-abbrev-file' skip writing empty tables.
+
 +++
 ** The new functions and commands 'text-property-search-forward' and
 'text-property-search-backward' have been added.  These provide an
diff --git a/lisp/abbrev.el b/lisp/abbrev.el
index cddce8f529..e1fd366ba9 100644
--- a/lisp/abbrev.el
+++ b/lisp/abbrev.el
@@ -896,24 +896,22 @@ unexpand-abbrev
 
 (defun abbrev--write (sym)
   "Write the abbrev in a `read'able form.
-Only writes the non-system abbrevs.
 Presumes that `standard-output' points to `current-buffer'."
-  (unless (or (null (symbol-value sym)) (abbrev-get sym :system))
-    (insert "    (")
-    (prin1 (symbol-name sym))
-    (insert " ")
-    (prin1 (symbol-value sym))
-    (insert " ")
-    (prin1 (symbol-function sym))
-    (insert " :count ")
-    (prin1 (abbrev-get sym :count))
-    (when (abbrev-get sym :case-fixed)
-      (insert " :case-fixed ")
-      (prin1 (abbrev-get sym :case-fixed)))
-    (when (abbrev-get sym :enable-function)
-      (insert " :enable-function ")
-      (prin1 (abbrev-get sym :enable-function)))
-    (insert ")\n")))
+  (insert "    (")
+  (prin1 (symbol-name sym))
+  (insert " ")
+  (prin1 (symbol-value sym))
+  (insert " ")
+  (prin1 (symbol-function sym))
+  (insert " :count ")
+  (prin1 (abbrev-get sym :count))
+  (when (abbrev-get sym :case-fixed)
+    (insert " :case-fixed ")
+    (prin1 (abbrev-get sym :case-fixed)))
+  (when (abbrev-get sym :enable-function)
+    (insert " :enable-function ")
+    (prin1 (abbrev-get sym :enable-function)))
+  (insert ")\n"))
 
 (defun abbrev--describe (sym)
   (when (symbol-value sym)
@@ -934,31 +932,38 @@ insert-abbrev-table-description
   "Insert before point a full description of abbrev table named NAME.
 NAME is a symbol whose value is an abbrev table.
 If optional 2nd arg READABLE is non-nil, a human-readable description
-is inserted.  Otherwise the description is an expression,
-a call to `define-abbrev-table', which would
-define the abbrev table NAME exactly as it is currently defined.
-
-Abbrevs marked as \"system abbrevs\" are omitted."
+is inserted.
+
+If READABLE is nil, an expression is inserted.  The expression is
+a call to `define-abbrev-table' that when evaluated will define
+the abbrev table NAME exactly as it is currently defined.
+Abbrevs marked as \"system abbrevs\" are ignored.  If the
+resulting expression would not define any abbrevs, nothing is
+inserted."
   (let ((table (symbol-value name))
         (symbols ()))
-    (mapatoms (lambda (sym) (if (symbol-value sym) (push sym symbols))) table)
-    (setq symbols (sort symbols 'string-lessp))
-    (let ((standard-output (current-buffer)))
-      (if readable
-	  (progn
-	    (insert "(")
-	    (prin1 name)
-	    (insert ")\n\n")
-	    (mapc 'abbrev--describe symbols)
-	    (insert "\n\n"))
-	(insert "(define-abbrev-table '")
-	(prin1 name)
-	(if (null symbols)
-	    (insert " '())\n\n")
-	  (insert "\n  '(\n")
-	  (mapc 'abbrev--write symbols)
-	  (insert "   ))\n\n")))
-      nil)))
+    (mapatoms (lambda (sym)
+                (if (and (symbol-value sym) (or readable (not (abbrev-get sym :system))))
+                    (push sym symbols)))
+              table)
+    (when symbols
+      (setq symbols (sort symbols 'string-lessp))
+      (let ((standard-output (current-buffer)))
+        (if readable
+            (progn
+              (insert "(")
+              (prin1 name)
+              (insert ")\n\n")
+              (mapc 'abbrev--describe symbols)
+              (insert "\n\n"))
+          (insert "(define-abbrev-table '")
+          (prin1 name)
+          (if (null symbols)
+              (insert " '())\n\n")
+            (insert "\n  '(\n")
+            (mapc 'abbrev--write symbols)
+            (insert "   ))\n\n")))
+        nil))))
 
 (defun define-abbrev-table (tablename definitions
                                       &optional docstring &rest props)
-- 
2.19.0