[JimmXinu]

I think I've figured out how to call Calibre template/formatter instead of Python's. And how to add the pre-existing Catalog template values, assuming I'm not abusing the privilege.

            mi = self.db.get_metadata(book['id'],index_is_id=True)
            generated_html = P('catalog/template.xhtml', data=True).decode('utf-8')

            ## brute force copy any old catalog values such as {xmlns}
            for k in args:
                if not mi.has_key(k):
                    self.opts.log.error("Setting %s -> %s"%(k,args[k]))
                    mi.__setattr__(k,args[k])

            from calibre.ebooks.metadata.book.formatter import SafeFormat
            generated_html = SafeFormat().unsafe_format(generated_html,
                                                        {},
                                                        mi)

Is this an acceptable approach?


The best (calibre) template expression I've found so far that will allow a template.xhtml to use a custom column only if it exists in the library is:

{title:'cmp(field_exists("#wordcount"),1,'',template("[[#wordcount]]"),'')'}

Or with prefix & suffix:

{title:'cmp(field_exists("#wordcount"),1,'',template("[[#wordcount]]"),'')'|<tr><td>Words: |</td></tr>}

...where title is arbitrary because I didn't see another way.

Any suggestions for a better expression? I'm trying to avoid needing the user to add template functions.