From 98070ce97fe47f395e2524b40a01e65c954bc97f Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sat, 9 Jan 2016 14:50:49 +0530
Subject: [PATCH] Tag Mapper: Do not allow the user to create rules with
 invalid regular expressions

---
 src/calibre/ebooks/metadata/tag_mapper.py |  7 +++++--
 src/calibre/gui2/tag_mapper.py            | 12 ++++++++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/calibre/ebooks/metadata/tag_mapper.py b/src/calibre/ebooks/metadata/tag_mapper.py
index 5b92c8468f..e8a2d54c3d 100644
--- a/src/calibre/ebooks/metadata/tag_mapper.py
+++ b/src/calibre/ebooks/metadata/tag_mapper.py
@@ -10,6 +10,9 @@ from collections import deque
 REGEX_FLAGS = regex.VERSION1 | regex.WORD | regex.FULLCASE | regex.IGNORECASE | regex.UNICODE
 
 
+def compile_pat(pat):
+    return regex.compile(pat, flags=REGEX_FLAGS)
+
 def matcher(rule):
     mt = rule['match_type']
     if mt == 'one_of':
@@ -21,11 +24,11 @@ def matcher(rule):
         return lambda x: x not in tags
 
     if mt == 'matches':
-        pat = regex.compile(rule['query'], flags=REGEX_FLAGS)
+        pat = compile_pat(rule['query'])
         return lambda x: pat.match(x) is not None
 
     if mt == 'not_matches':
-        pat = regex.compile(rule['query'], flags=REGEX_FLAGS)
+        pat = compile_pat(rule['query'])
         return lambda x: pat.match(x) is None
 
     return lambda x: False
diff --git a/src/calibre/gui2/tag_mapper.py b/src/calibre/gui2/tag_mapper.py
index 6de73f1fd9..6bf5cf4943 100644
--- a/src/calibre/gui2/tag_mapper.py
+++ b/src/calibre/gui2/tag_mapper.py
@@ -14,7 +14,7 @@ from PyQt5.Qt import (
     QStaticText, Qt, QStyle, QToolButton, QInputDialog, QMenu
 )
 
-from calibre.ebooks.metadata.tag_mapper import map_tags
+from calibre.ebooks.metadata.tag_mapper import map_tags, compile_pat
 from calibre.gui2 import error_dialog, elided_text, Application, question_dialog
 from calibre.gui2.widgets2 import Dialog
 from calibre.utils.config import JSONConfig
@@ -60,6 +60,7 @@ class RuleEdit(QWidget):
         h.addWidget(q)
         for action, text in self.MATCH_TYPE_MAP.iteritems():
             q.addItem(text, action)
+        q.currentIndexChanged.connect(self.update_state)
         self.la2 = la = QLabel(':\xa0')
         h.addWidget(la)
         self.query = q = QLineEdit(self)
@@ -83,7 +84,7 @@ class RuleEdit(QWidget):
         replace = self.action.currentData() == 'replace'
         self.la3.setVisible(replace), self.replace.setVisible(replace)
         tt = _('A comma separated list of tags')
-        if 'pattern' in self.match_type.currentData():
+        if 'matches' in self.match_type.currentData():
             tt = _('A regular expression')
         self.query.setToolTip(tt)
 
@@ -114,6 +115,13 @@ class RuleEdit(QWidget):
             error_dialog(self, _('Query required'), _(
                 'You must provide a value for the tag to match'), show=True)
             return False
+        if 'matches' in rule['match_type']:
+            try:
+                compile_pat(rule['query'])
+            except Exception:
+                error_dialog(self, _('Query invalid'), _(
+                    '%s is not a valid regular expression') % rule['query'], show=True)
+                return False
         return True
 
 class RuleEditDialog(Dialog):