Accessing custom metadata from Web Engine gallery

Have things advanced in Lightroom to support access to custom metadata in a web gallery plugin?

I don't totally understand the web engine, but I was able to modify the SDK example "mysample.lrwebengine" to show another plugin's custom metadata field underneath the image shown on "large.html".  The basic idea is to map the image proxy returned by getImage(index) to its corresponding LrPhoto in the catalog, using the image proxy's "imageID" property.  That "imageID" property is the the same as the underlying photo's "localIdentifier" property.  Once you have an LrPhoto, you can use the photo:getPropertyForPlugin() method to retrieve the custom metadata field for any plugin.

Here's a modified version of "large.html" that displays the metadata field "file" of the plugin "com.johnrellis.anyfile" underneath the image:

<%
--[[ Define some variables to make locating other resources easier.]]

    local image = getImage( index )
    local theRoot = ".."
    local others = "."
    local mySize = "large"

--[[ Code added by John R. Ellis ]]
local LrApplication = import 'LrApplication'
local catalog = LrApplication.activeCatalog ()
local idToPhoto = {}
for _, photo in ipairs (catalog:getAllPhotos ()) do
    idToPhoto [photo.localIdentifier] = photo
    end
local photo = idToPhoto [image.imageID]
local anyfileFile = photo:getPropertyForPlugin ("com.johnrellis.anyfile", "file")
--[[ End code added by John R. Ellis ]]
%>


<% --[[ Include the page header]] %>
<%@ include file="header.html" %>
<div>
    <ul>
      <lr:Pagination>
        <lr:PreviousEnabled>
          <li><a href="$link">Previous</a></li>
        </lr:PreviousEnabled>
        <lr:PreviousDisabled>
          <li>Previous</li>
        </lr:PreviousDisabled>
        <li><a href="$gridPageLink">Index</a></li>
        <lr:NextEnabled>
          <li><a href="$link">Next</a></li>
        </lr:NextEnabled>
        <lr:NextDisabled>
          <li>Next</li>
        </lr:NextDisabled>
      </lr:Pagination>
    </ul>
</div>
 <a href="$gridPageLink">
<img src="bin/images/large/<%= image.exportFilename %>.jpg" />
</a>

<pre> <%= --[[ Code added by John R. Ellis ]]
"Value of com.johnrellis.anyfile:file -- " .. (anyfileFile or "") 
--[[ End of code added by John R. Ellis ]] %> 
</pre>

<xmpl:aQuote>You know what they say:<br>
  <xmpl:saying> <br />....how interesting!<br /></xmpl:saying>
</xmpl:aQuote>

<% --[[ Include the page footer]] %>
<%@ include file="footer.html" %>