From 36257b1b3af37a7b34b56379de7574e51d3ba3d2 Mon Sep 17 00:00:00 2001
From: Gaetan Delannay <gaetan.delannay@gmail.com>
Date: Tue, 15 May 2012 23:13:30 +0200
Subject: [PATCH] appy.diff: bugfix (avoid infinite loop between m_getHtmlDiff
 and m_getReplacement) and better recovery when the Merger fails to manage
 overlaps (thhe whole line is then considered as having been deleted and
 replaced by something completely different, which is not really the case but
 at least is shows a simplified diff instead of crashing. appy.shared: bugfix
 in the XhtmlCleaner that now returns result as a str and not a unicode.

---
 shared/diff.py       | 28 ++++++++++++++++++++++++----
 shared/xml_parser.py |  2 +-
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/shared/diff.py b/shared/diff.py
index 8a9c4b7..e2b0aa0 100644
--- a/shared/diff.py
+++ b/shared/diff.py
@@ -10,6 +10,10 @@ htmlTag = re.compile('<(?P<tag>\w+)( .*?)?>(.*)</(?P=tag)>')
 class Merger:
     '''This class allows to merge 2 lines of text, each containing inserts and
        deletions.'''
+
+    # Exception that may be raised by this class if the merge fails.
+    class MergeError(Exception): pass
+
     def __init__(self, lineA, lineB, previousDiffs, differ):
         # lineA comes "naked": any diff previously found on it was removed from
         # it (ie, deleted text has been completely removed, while inserted text
@@ -148,7 +152,8 @@ class Merger:
                 # Invariant: at this point, we should find what remains in
                 # oldText at self.lineB[self.i:].
                 if not self.lineB[self.i:].startswith(oldText):
-                    raise 'Error!!!!'
+                    raise self.MergeError('An error occurred while computing ' \
+                                          'overlapping diffs.')
                 res += self.differ.getModifiedChunk(oldText, 'insert', '',
                                                     msg=oldDiff.group(2))
                 self.i += len(oldText)
@@ -584,8 +589,15 @@ class HtmlDiff:
                 # Merge potential previous inner diff tags that were found (but
                 # extracted from) lineA.
                 if previousDiffsA:
-                    merger = Merger(lineA, add, previousDiffsA, self)
-                    add = merger.merge()
+                    try:
+                        merger = Merger(lineA, add, previousDiffsA, self)
+                        add = merger.merge()
+                    except Merger.MergeError, e:
+                        # The merge algorithm has made a burn out. Simplify and
+                        # consider lineA has having been completely deleted and
+                        # lineB has completely inserted.
+                        add = self.getModifiedChunk(lineA, 'delete', sep) + \
+                              self.getModifiedChunk(lineB, 'insert', sep)
                 # Rewrap line into outerTagA if lineA was a line tagged as
                 # previously inserted.
                 if outerTagA:
@@ -633,7 +645,15 @@ class HtmlDiff:
                     # Was a deletion, not a replacement
                     add = self.getModifiedChunk(chunkA, 'delete', sep)
                 else: # At least, a true replacement
-                    add = self.getReplacement(chunkA, chunkB, sep)
+                    if (sep == ' ') and (sep not in chunkA) and \
+                       (sep not in chunkB):
+                        # By going here, we avoid infinite loops that may occur
+                        # between m_getHtmlDiff and m_getReplacement
+                        # (called below).
+                        add = self.getModifiedChunk(chunkA, 'delete', sep) + \
+                              self.getModifiedChunk(chunkB, 'insert', sep)
+                    else:
+                        add = self.getReplacement(chunkA, chunkB, sep)
             if add: res += self.getDumpPrefix(res, add, previousAdd, sep) + add
             previousAdd = add
         return res
diff --git a/shared/xml_parser.py b/shared/xml_parser.py
index 12e6941..cd8f649 100644
--- a/shared/xml_parser.py
+++ b/shared/xml_parser.py
@@ -934,7 +934,7 @@ class XhtmlCleaner(XmlParser):
         # 'ignoreContent' is True if, within the currently ignored tag, we must
         # also ignore its content.
         self.env.ignoreContent = False
-        return self.parse('<x>%s</x>' % s)
+        return self.parse('<x>%s</x>' % s).encode('utf-8')
 
     def startDocument(self):
         # The result will be cleaned XHTML, joined from self.res.