check for db limits on content tag asset name sync

test plan:
* add a wiki page to a course
* add the wiki page as a module item
* edit the module item title to be
more than 255 characters long
* should not return an 'unexpected error'

fixes #CNVS-3052 frd

Change-Id: I8c6f18a8da7ecdce9a53f88d40ce82fd6d4e85c8
Reviewed-on: https://gerrit.instructure.com/22173
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>

app/models/content_tag.rb

@@ -165,17 +165,25 @@ class ContentTag < ActiveRecord::Base
   def content_or_self
     content || self
   end
-  
+
+  def asset_safe_title(column)
+    name = self.title.to_s
+    if (limit = self.content.class.try(:columns_hash)[column].try(:limit)) && name.length > limit
+      name = name[0, limit][/.{0,#{limit}}/mu]
+    end
+    name
+  end
+
   def update_asset_name!
     return unless self.sync_title_to_asset_title?
     correct_context = self.content && self.content.respond_to?(:context) && self.content.context == self.context
     if correct_context
       if self.content.respond_to?("name=") && self.content.respond_to?("name") && self.content.name != self.title
-        self.content.update_attribute(:name, self.title)
+        self.content.update_attribute(:name, asset_safe_title('name'))
       elsif self.content.respond_to?("title=") && self.content.title != self.title
-        self.content.update_attribute(:title, self.title)
+        self.content.update_attribute(:title, asset_safe_title('title'))
       elsif self.content.respond_to?("display_name=") && self.content.display_name != self.title
-        self.content.update_attribute(:display_name, self.title)
+        self.content.update_attribute(:display_name, asset_safe_title('display_name'))
       end
     end
   end

spec/models/content_tag_spec.rb

@@ -161,6 +161,21 @@ describe ContentTag do
     @assignment.title.should == 'some assignment (renamed)'
   end
 
+  it "should not attempt to update asset name attribute if it's over the db limit" do
+    course
+    @page = @course.wiki.wiki_pages.create!(:title => "some page")
+    @page.workflow_state = 'unpublished'
+    @page.save!
+    @module = @course.context_modules.create!(:name => "module")
+    @tag = @module.add_item({:type => 'WikiPage', :title => 'oh noes!' * 35, :id => @page.id})
+    @tag.workflow_state.should == 'unpublished'
+
+    @tag.update_asset_name!
+
+    @page.reload
+    @tag.title[0, 250].should == @page.title[0, 250]
+  end
+
   it "should publish/unpublish the tag if the linked wiki page is published/unpublished" do
     course
     @page = @course.wiki.wiki_pages.create!(:title => "some page")