Improve dashboard note view and add tests

Update the `#first_line_in_markdown` method so that the first line of
parsed text is displayed more reliably, and the continuation indicators
("...") are displayed in all cases where the note is truncated.

Also add Rspec tests for `EventsHelper#event_note`.

app/helpers/events_helper.rb

@@ -137,7 +137,7 @@ module EventsHelper
   def event_note(text)
     text = first_line_in_markdown(text, 150)
-    sanitize(text, tags: %w(a img b pre p))
+    sanitize(text, tags: %w(a img b pre code p))
   end
   def event_commit_title(message)

app/helpers/gitlab_markdown_helper.rb

@@ -56,16 +56,9 @@ module GitlabMarkdownHelper
   # +max_chars+ limit.  If the length limit falls within a tag's contents, then
   # the tag contents are truncated without removing the closing tag.
   def first_line_in_markdown(text, max_chars = nil)
-    line = text.split("\n").find do |i|
-      i.present? && markdown(i).present?
-    end
-
-    if line
-      md = markdown(line)
-      truncated = truncate_visible(md, max_chars || md.length)
-    end
-    truncated
+    md = markdown(text).strip
+    truncate_visible(md, max_chars || md.length) if md.present?
   end
   def render_wiki_content(wiki_page)
@@ -221,22 +214,44 @@ module GitlabMarkdownHelper
   def truncate_visible(text, max_chars)
     doc = Nokogiri::HTML.fragment(text)
     content_length = 0
+    truncated = false
     doc.traverse do |node|
       if node.text? || node.content.empty?
-        if content_length >= max_chars
+        if truncated
           node.remove
           next
         end
+        # Handle line breaks within a node
+        if node.content.strip.lines.length > 1
+          node.content = "#{node.content.lines.first.chomp}..."
+          truncated = true
+        end
+
         num_remaining = max_chars - content_length
         if node.content.length > num_remaining
           node.content = node.content.truncate(num_remaining)
+          truncated = true
         end
         content_length += node.content.length
       end
+
+      truncated = truncate_if_block(node, truncated)
     end
     doc.to_html
   end
+
+  # Used by #truncate_visible.  If +node+ is the first block element, and the
+  # text hasn't already been truncated, then append "..." to the node contents
+  # and return true.  Otherwise return false.
+  def truncate_if_block(node, truncated)
+    if node.element? && node.description.block? && !truncated
+      node.content = "#{node.content}..." if node.next_sibling
+      true
+    else
+      truncated
+    end
+  end
 end

spec/helpers/events_helper_spec.rb

+require 'spec_helper'
+
+describe EventsHelper do
+  include ApplicationHelper
+  include GitlabMarkdownHelper
+
+  it 'should display one line of plain text without alteration' do
+    input = 'A short, plain note'
+    expect(event_note(input)).to match(input)
+    expect(event_note(input)).not_to match(/\.\.\.\z/)
+  end
+
+  it 'should display inline code' do
+    input = 'A note with `inline code`'
+    expected = 'A note with <code>inline code</code>'
+
+    expect(event_note(input)).to match(expected)
+  end
+
+  it 'should truncate a note with multiple paragraphs' do
+    input = "Paragraph 1\n\nParagraph 2"
+    expected = 'Paragraph 1...'
+
+    expect(event_note(input)).to match(expected)
+  end
+
+  it 'should display the first line of a code block' do
+    input = "```\nCode block\nwith two lines\n```"
+    expected = '<pre><code class="">Code block...</code></pre>'
+
+    expect(event_note(input)).to match(expected)
+  end
+
+  it 'should truncate a single long line of text' do
+    text = 'The quick brown fox jumped over the lazy dog twice' # 50 chars
+    input = "#{text}#{text}#{text}#{text}" # 200 chars
+    expected = "#{text}#{text}".sub(/.{3}/, '...')
+
+    expect(event_note(input)).to match(expected)
+  end
+
+  it 'should preserve a link href when link text is truncated' do
+    text = 'The quick brown fox jumped over the lazy dog' # 44 chars
+    input = "#{text}#{text}#{text} " # 133 chars
+    link_url = 'http://example.com/foo/bar/baz' # 30 chars
+    input << link_url
+    expected_link_text = 'http://example...</a>'
+
+    expect(event_note(input)).to match(link_url)
+    expect(event_note(input)).to match(expected_link_text)
+  end
+end