Page will try to render itself in revise method, and behave appropriately if markup engine fails [inspired by Denis]

app/controllers/file_controller.rb

@@ -94,9 +94,15 @@ class FileController < ApplicationController
       page_content = entry.get_input_stream.read
       logger.info "Processing page '#{page_name}'"
       begin
-        if @wiki.read_page(@web.address, page_name)
-          logger.info "Page '#{page_name}' already exists. Adding a new revision to it."
-          wiki.revise_page(@web.address, page_name, page_content, Time.now, @author)
+        existing_page = @wiki.read_page(@web.address, page_name)
+        if existing_page
+          if existing_page.content == page_content
+            logger.info "Page '#{page_name}' with the same content already exists. Skipping."
+            next
+          else
+            logger.info "Page '#{page_name}' already exists. Adding a new revision to it."
+            wiki.revise_page(@web.address, page_name, page_content, Time.now, @author)
+          end
         else
           wiki.write_page(@web.address, page_name, page_content, Time.now, @author)
         end

app/models/page.rb

@@ -21,7 +21,7 @@ class Page
       raise Instiki::ValidationError.new(
           "You have tried to save page '#{name}' without changing its content")
     end
-  
+
     # A user may change a page, look at it and make some more changes - several times.
     # Not to record every such iteration as a new revision, if the previous revision was done 
     # by the same author, not more than 30 minutes ago, then update the last revision instead of
@@ -33,8 +33,14 @@ class Page
     else
       @revisions << Revision.new(self, @revisions.length, content, created_at, author)
     end
+
+    self.revisions.last.force_rendering
+    # at this point the page may not be inserted in the web yet, and therefore 
+    # references to the page itself are rendered as "unresolved". Clearing the cache allows 
+    # the page to re-render itself once again, hopefully _after_ it is inserted in the web
+    self.revisions.last.clear_display_cache
     
-    web.refresh_pages_with_references(name) if @revisions.length == 1
+    web.refresh_pages_with_references(@name) if @revisions.length == 1
   end
 
   def rollback(revision_number, created_at, author_ip = nil)
@@ -79,14 +85,16 @@ class Page
     web.make_link(author, nil, options)
   end
 
-  private
-    def continous_revision?(created_at, author)
-      @revisions.last.author == author && @revisions.last.created_at + 30.minutes > created_at
-    end
 
-    # Forward method calls to the current revision, so the page responds to all revision calls
-    def method_missing(method_symbol)
-      revisions.last.send(method_symbol)
-    end
+  private
+
+  def continous_revision?(created_at, author)
+    @revisions.last.author == author && @revisions.last.created_at + 30.minutes > created_at
+  end
+
+  # Forward method calls to the current revision, so the page responds to all revision calls
+  def method_missing(method_symbol)
+    revisions.last.send(method_symbol)
+  end
 
 end

app/models/revision.rb

@@ -79,5 +79,21 @@ class Revision
   def display_content_for_export
     WikiContent.new(self, {:mode => :export} )
   end
+  
+  def force_rendering
+    begin
+      display_content
+    rescue Exception => e
+      ApplicationController.logger.error "Failed rendering page #{@name}"
+      ApplicationController.logger.error e
+      message = e.message.gsub(/\n/, '<br/>')
+      # substitute content with an error message
+      content = <<-EOL
+          <p>Markup engine has failed to render this page, raising the following error:</p>
+          <p>#{message}</p>
+      EOL
+      raise e
+    end
+  end
 
 end