Prevent empty values for the "name" attribute name on HTML anchor tags, and...

Prevent empty values for the "name" attribute name on HTML anchor tags, and add an "id" to its parent "div" container.

Signed-off-by: Chris Lamb <lamby@debian.org>

diffoscope/presenters/html/html.py

@@ -158,11 +158,12 @@ def output_visual(visual, path, indentstr, indentnum):
     logger.debug('including image for %s', visual.source)
     indent = tuple(indentstr * (indentnum + x) for x in range(3))
     anchor = output_anchor(path)
+    id = 'id="{}"'.format(anchor) if anchor else ''
     return u"""{0[0]}<div class="difference">
 {0[1]}<div class="diffheader">
 {0[1]}<div class="diffcontrol">⊟</div>
-{0[1]}<div><span class="source">{1}</span>
-{0[2]}<a class="anchor" href="#{2}" name="{2}">\xb6</a>
+{0[1]}<div {5}><span class="source">{1}</span>
+{0[2]}<a class="anchor" href="#{2}">\xb6</a>
 {0[1]}</div>
 {0[1]}</div>
 {0[1]}<div class="difference"><img src=\"data:{3},{4}\" alt=\"compared images\" /></div>
@@ -172,12 +173,14 @@ def output_visual(visual, path, indentstr, indentnum):
         anchor,
         visual.data_type,
         visual.content,
+        id,
     )
 
 
 def output_node_frame(difference, path, indentstr, indentnum, body):
     indent = tuple(indentstr * (indentnum + x) for x in range(3))
     anchor = output_anchor(path)
+    id = 'id="{}"'.format(anchor) if anchor else ''
     dctrl_class, dctrl = (
         ("diffcontrol", u'⊟')
         if difference.has_visible_children()
@@ -186,8 +189,8 @@ def output_node_frame(difference, path, indentstr, indentnum, body):
     if difference.source1 == difference.source2:
         header = u"""{0[1]}<div class="{1}">{2}</div>
 {0[1]}<div><span class="diffsize">{3}</span></div>
-{0[1]}<div><span class="source">{5}</span>
-{0[2]}<a class="anchor" href="#{4}" name="{4}">\xb6</a>
+{0[1]}<div {6}><span class="source">{5}</span>
+{0[2]}<a class="anchor" href="#{4}">\xb6</a>
 {0[1]}</div>
 """.format(
             indent,
@@ -196,13 +199,14 @@ def output_node_frame(difference, path, indentstr, indentnum, body):
             sizeof_fmt(difference.size()),
             anchor,
             html.escape(difference.source1),
+            id,
         )
     else:
         header = u"""{0[1]}<div class="{1} diffcontrol-double">{2}</div>
 {0[1]}<div><span class="diffsize">{3}</span></div>
 {0[1]}<div><span class="source">{5}</span> vs.</div>
-{0[1]}<div><span class="source">{6}</span>
-{0[2]}<a class="anchor" href="#{4}" name="{4}">\xb6</a>
+{0[1]}<div {7}><span class="source">{6}</span>
+{0[2]}<a class="anchor" href="#{4}">\xb6</a>
 {0[1]}</div>
 """.format(
             indent,
@@ -212,6 +216,7 @@ def output_node_frame(difference, path, indentstr, indentnum, body):
             anchor,
             html.escape(difference.source1),
             html.escape(difference.source2),
+            id,
         )
 
     return PartialString.numl(