Quiz math fixup bug fixes

closes LS-1685
flag=none

test plan:
  - when a quiz is fixed-up, the tooltips on equation answers should
    be reasonable.
  - if we find inline latex burried in the sea of html-ish text
    it's extracted and turned into an equation image. Sadly
    I don't remember what quiz+question I discovered this on
    (though it was near the top of peyton's course)
  - when fixup generates equation images, the title has its closing
    quote, so the tooltip looks correct.

Change-Id: I21201b094c46ee057d1a6f779d120db303e31bca
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/254544
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Nate Armstrong <narmstrong@instructure.com>
QA-Review: Robin Kuss <rkuss@instructure.com>
Product-Review: Ed Schiebel <eschiebel@instructure.com>

lib/quiz_math_data_fixup.rb

@@ -25,7 +25,7 @@ module QuizMathDataFixup
     else
       questions = quiz_or_bank.quiz_questions
     end
-    questions = questions.where("updated_at>?", check_date) if check_date
+    questions = questions.where('updated_at>?', check_date) if check_date
     questions.find_each do |quiz_question|
       begin
         old_data = quiz_question.question_data.to_hash
@@ -63,13 +63,21 @@ module QuizMathDataFixup
   end
 
   def fixup_question_data(data)
-    %i(neutral_comments_html correct_comments_html incorrect_comments_html).each do |key|
-      if data[key].present?
-        data[key] = fixup_html(data[key])
-      end
+    %i[neutral_comments_html correct_comments_html incorrect_comments_html].each do |key|
+      data[key] = fixup_html(data[key]) if data[key].present?
     end
     data[:answers].each_with_index do |answer, index|
-      %i(html comments_html).each { |key| answer[key] = fixup_html(answer[key]) if answer[key].present? }
+      %i[html comments_html].each do |key|
+        # if there's html, the text field is used as the title attribute/tooltip
+        # clear it out if we updated the html because it's probably hosed.
+
+        if answer[key].present?
+          answer[key] = fixup_html(answer[key])
+
+          text_key = key.to_s.sub(/html/, 'text')
+          answer[text_key] = '' if answer[text_key].present?
+        end
+      end
       data[:answers][index] = answer
     end
     data
@@ -78,17 +86,28 @@ module QuizMathDataFixup
   def fixup_html(html)
     return html unless html
     html = Nokogiri::HTML::DocumentFragment.parse(html)
-    html.search('[id^="MathJax"]').each(&:remove)
     if html.children.length == 1 && html.children[0].node_type == Nokogiri::XML::Node::TEXT_NODE
+      # look for an equation_images URL in the text and extract the latex
       m = %r{equation_images\/([^\s]+)}.match(html.content)
       if m && m[1]
         code = URI.unescape(URI.unescape(m[1]))
         html =
-          "<img class='equation_image' src='/equation_images/#{m[1]}' alt='LaTeX: #{
+          "<img class='equation_image' src='/equation_images/#{m[1]}' alt='LaTeX: #{code}' title='#{
             code
-          }' title='#{code} data-equation-content='#{code}>"
+          }' data-equation-content='#{code}'/>"
+      else
+        # look for \(inline latex\) and extract it
+        m = html.content.match(/\\\(((?!\\\)).+)\\\)/)
+        if m && m[1]
+          code = URI.unescape(URI.unescape(m[1]))
+          html =
+            "<img class='equation_image' src='/equation_images/#{m[1]}' alt='LaTeX: #{
+              code
+            }' title='#{code}' data-equation-content='#{code}'/>"
+        end
       end
-      return html
+      html.search('[id^="MathJax"]').each(&:remove)
+      return html.to_s
     end
     html.search('.math_equation_latex').each do |latex|
       # find MathJax generated children, extract the eq's mathml
@@ -107,17 +126,16 @@ module QuizMathDataFixup
         latex.replace(
           "<img class='equation_image' src='/equation_images/#{escaped}' alt='LaTeX: #{
             code
-          }' title='#{code}>"
+          }' title='#{code}' data-equation-content='#{code}'/>"
         )
       elsif mml
         latex.replace(
-          "<math xmlns='http://www.w3.org/1998/Math/MathML' class='math_equation_mml'>#{
-            mml
-          }</math>"
+          "<math xmlns='http://www.w3.org/1998/Math/MathML' class='math_equation_mml'>#{mml}</math>"
         )
       end
     end
 
+    html.search('[id^="MathJax"]').each(&:remove)
     html.search('span.hidden-readable').each(&:remove)
 
     html.to_s
@@ -128,6 +146,8 @@ module QuizMathDataFixup
   end
 
   def check_or_fix_question_banks(batch_of_ids)
-    AssessmentQuestionBank.where(id: batch_of_ids).find_each { |q| fixup_quiz_questions_with_bad_math(q, question_bank: true) }
+    AssessmentQuestionBank.where(id: batch_of_ids).find_each do |q|
+      fixup_quiz_questions_with_bad_math(q, question_bank: true)
+    end
   end
 end

lib/user_content.rb

@@ -67,7 +67,7 @@ module UserContent
       # inadvertently saved the hidden-readable span, causing
       # them to multiply everytime the entity is edited.
       # Strip the ones that shouldn't be there before adding a new one
-      node.next.remove while node.next && node.next['class'] == 'hidden-readable'
+      node.next_element.remove while node.next_element && node.next_element['class'] == 'hidden-readable'
 
       if !use_updated_math_rendering
         mathml = UserContent.latex_to_mathml(equation)