Handle deleted wiki page versions (#10852).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@10684 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/wiki_content.rb

@@ -115,10 +115,18 @@ class WikiContent < ActiveRecord::Base
 
     # Returns the previous version or nil
     def previous
-      @previous ||= WikiContent::Version.find(:first,
-                                              :order => 'version DESC',
-                                              :include => :author,
-                                              :conditions => ["wiki_content_id = ? AND version < ?", wiki_content_id, version])
+      @previous ||= WikiContent::Version.
+        reorder('version DESC').
+        includes(:author).
+        where("wiki_content_id = ? AND version < ?", wiki_content_id, version).first
+    end
+
+    # Returns the next version or nil
+    def next
+      @next ||= WikiContent::Version.
+        reorder('version ASC').
+        includes(:author).
+        where("wiki_content_id = ? AND version > ?", wiki_content_id, version).first
     end
   end
 end

app/models/wiki_page.rb

@@ -111,11 +111,12 @@ class WikiPage < ActiveRecord::Base
 
   def diff(version_to=nil, version_from=nil)
     version_to = version_to ? version_to.to_i : self.content.version
-    version_from = version_from ? version_from.to_i : version_to - 1
-    version_to, version_from = version_from, version_to unless version_from < version_to
-
     content_to = content.versions.find_by_version(version_to)
-    content_from = content.versions.find_by_version(version_from)
+    content_from = version_from ? content.versions.find_by_version(version_from.to_i) : content_to.previous
+
+    if content_from.version > content_to.version
+      content_to, content_from = content_from, content_to
+    end
 
     (content_to && content_from) ? WikiDiff.new(content_to, content_from) : nil
   end