bug#24997: 26.0.50; ibuffer-decompose-filter has side effects on error

[Tino Calancha]

Previous patch had undesirable side effects on `ibuffer-saved-filters'.
Updated patch:

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>From ffca1e2c713f39a0782b359279693e9e4245f791 Mon Sep 17 00:00:00 2001
From: Tino Calancha <tino.calancha@gmail.com>
Date: Sun, 27 Nov 2016 12:46:19 +0900
Subject: [PATCH] ibuffer-decompose-filter: Avoid side effects on error

* lisp/ibuf-ext.el (ibuffer-decompose-filter):
Update 'ibuffer-filtering-qualifiers' only if there is no error (Bug#24997).
---
 lisp/ibuf-ext.el | 39 +++++++++++++++++----------------------
 1 file changed, 17 insertions(+), 22 deletions(-)

diff --git a/lisp/ibuf-ext.el b/lisp/ibuf-ext.el
index 5ef0746..63db1e6 100644
--- a/lisp/ibuf-ext.el
+++ b/lisp/ibuf-ext.el
@@ -840,29 +840,24 @@ ibuffer-decompose-filter
 be a complex filter like (OR [name: foo] [mode: bar-mode]), will be
 turned into two separate filters [name: foo] and [mode: bar-mode]."
   (interactive)
-  (when (null ibuffer-filtering-qualifiers)
+  (unless ibuffer-filtering-qualifiers
     (error "No filters in effect"))
-  (let ((lim (pop ibuffer-filtering-qualifiers)))
-    (pcase (car lim)
-      (`or
-       (setq ibuffer-filtering-qualifiers (append
-                                         (cdr lim)
-                                         ibuffer-filtering-qualifiers)))
-      (`saved
-       (let ((data
-             (assoc (cdr lim)
-                    ibuffer-saved-filters)))
-        (unless data
-          (ibuffer-filter-disable)
-          (error "Unknown saved filter %s" (cdr lim)))
-        (setq ibuffer-filtering-qualifiers (append
-                                           (cadr data)
-                                           ibuffer-filtering-qualifiers))))
-      (`not
-       (push (cdr lim)
-            ibuffer-filtering-qualifiers))
-      (_
-       (error "Filter type %s is not compound" (car lim)))))
+  (let* ((filters ibuffer-filtering-qualifiers)
+         (head (cdar filters))
+         (tail (cdr filters))
+         (value
+          (pcase (caar filters)
+            (`or (nconc head tail))
+            (`saved
+             (let ((data (assoc head ibuffer-saved-filters)))
+               (unless data
+                 (ibuffer-filter-disable)
+                 (error "Unknown saved filter %s" head))
+               (append (cadr data) tail)))
+            (`not (cons head tail))
+            (_
+             (error "Filter type %s is not compound" (caar filters))))))
+    (setq ibuffer-filtering-qualifiers value))
   (ibuffer-update nil t))
 
 ;;;###autoload
-- 
2.10.2

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In GNU Emacs 26.0.50.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.3)
 of 2016-11-26 built on calancha-pc
Repository revision: 416adda38521c6246f77877c57843264fa4ae711