From 2aa4f7c70bb5749e714dc2d2b3044b1e872b292e Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Wed, 25 Jul 2012 10:14:40 +0530
Subject: [PATCH] Conversion: Ignore invalid chapter detection and level n ToC
 expressions instead of erroring out

---
 .../ebooks/oeb/transforms/structure.py        | 26 +++++++++++++++----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/calibre/ebooks/oeb/transforms/structure.py b/src/calibre/ebooks/oeb/transforms/structure.py
index dd3db1415a..b90774bcc7 100644
--- a/src/calibre/ebooks/oeb/transforms/structure.py
+++ b/src/calibre/ebooks/oeb/transforms/structure.py
@@ -82,10 +82,17 @@ class DetectStructure(object):
 
     def detect_chapters(self):
         self.detected_chapters = []
+
+        def find_matches(expr, doc):
+            try:
+                return XPath(expr)(doc)
+            except:
+                self.log.warn('Invalid chapter expression, ignoring: %s'%expr)
+                return []
+
         if self.opts.chapter:
-            chapter_xpath = XPath(self.opts.chapter)
             for item in self.oeb.spine:
-                for x in chapter_xpath(item.data):
+                for x in find_matches(self.opts.chapter, item.data):
                     self.detected_chapters.append((item, x))
 
             chapter_mark = self.opts.chapter_mark
@@ -164,11 +171,19 @@ class DetectStructure(object):
         added = OrderedDict()
         added2 = OrderedDict()
         counter = 1
+
+        def find_matches(expr, doc):
+            try:
+                return XPath(expr)(doc)
+            except:
+                self.log.warn('Invalid ToC expression, ignoring: %s'%expr)
+                return []
+
         for document in self.oeb.spine:
             previous_level1 = list(added.itervalues())[-1] if added else None
             previous_level2 = list(added2.itervalues())[-1] if added2 else None
 
-            for elem in XPath(self.opts.level1_toc)(document.data):
+            for elem in find_matches(self.opts.level1_toc, document.data):
                 text, _href = self.elem_to_link(document, elem, counter)
                 counter += 1
                 if text:
@@ -178,7 +193,7 @@ class DetectStructure(object):
                     #node.add(_('Top'), _href)
 
             if self.opts.level2_toc is not None and added:
-                for elem in XPath(self.opts.level2_toc)(document.data):
+                for elem in find_matches(self.opts.level2_toc, document.data):
                     level1 = None
                     for item in document.data.iterdescendants():
                         if item in added:
@@ -196,7 +211,8 @@ class DetectStructure(object):
                             break
 
                 if self.opts.level3_toc is not None and added2:
-                    for elem in XPath(self.opts.level3_toc)(document.data):
+                    for elem in find_matches(self.opts.level3_toc,
+                            document.data):
                         level2 = None
                         for item in document.data.iterdescendants():
                             if item in added2: