Track diff per-target and set/unset showDiff

h/static/scripts/directives/annotation.coffee

@@ -45,6 +45,8 @@ AnnotationController = [
     @preview = 'no'
     @editing = false
     @embedded = false
+    @hasDiff = false
+    @showDiff = undefined
 
     highlight = annotator.tool is 'highlight'
     model = $scope.annotationGet()
@@ -206,8 +208,10 @@ AnnotationController = [
       @annotation.tags = ({text} for text in (model.tags or []))
 
       # Calculate the visual diff flags
-      @hasDiff = @annotation.target.filter((t) -> t.diffHTML?).length > 0
-      @showDiff ?= @hasDiff && @annotation.target.filter((t) -> t.diffHTML? and not t.diffCaseOnly).length > 0
+      @hasDiff = false
+      for t in @annotation.target or [] when t.diffHTML? and not t.diffCaseOnly
+        @hasDiff = t.hasDiff = true
+      @showDiff ?= @hasDiff or undefined
 
     # Export the baseURI for the share link
     this.baseURI = documentHelpers.baseURI

h/templates/client/annotation.html

@@ -44,14 +44,14 @@
 <section class="annotation-target"
          ng-repeat="target in vm.annotation.target track by $index">
   <blockquote class="annotation-quote"
-              ng-hide="vm.showDiff"
+              ng-hide="target.hasDiff && vm.showDiff"
               ng-bind-html="selector.exact"
               ng-repeat="selector in target.selector
                          | filter : {'type': 'TextQuoteSelector'}
                          track by $index"></blockquote>
   <blockquote class="annotation-quote"
               ng-bind-html="target.diffHTML"
-              ng-show="vm.showDiff"></blockquote>
+              ng-show="target.hasDiff && vm.showDiff"></blockquote>
 </section>
 <div class="small pull-right"
      ng-show="vm.hasDiff">