Great to hear that we will get an error message - hope the message at
least will give the user a hint of why it failed.
I do not know enough about the thing that XInclude is built on
(XPointer) to know all the possibilities. However, libxml2 does not
support xpointer="What?". For instance, if you run the command
xmllint --xinclude foo.xhtml
on a document which references <div id="What?"/> by way of
xpointer="What?", then you get an error message and inclusion does not
take place. The XInclude spec also says that xpointer attribute does not
support percent escaping, so that is also not an option.
Thus, I suspect that in order to use XInclude to embed the 'What?'
fragment, you would have to find another XPointer method than the pure
and direct xpointer="What?". For instance, perhaps one would have to
rely on features of "Allow advanced use of XInclude" to circumwent the
problem.
Currently, with regard to advanced use of XInclude, if you run "Copy as
Reference", and XXE detects that there is a id="foo", then it gives
priority to using xpointer="foo". And this seems to be the case, also
when the id contains special characters such as id="foo?". But one
possible workaround could be to to make sure - when Advanced Include is
enabled - that "Copy as References" tries one of the advanced options if
the simple option fails.
Anyway, as long as it can be done in an interoperatable way, I agree
that it would be very cool if you can make 'Copy as Reference' work even
with an ID like 'What?'.
Leif
Hussein Shafie on 2023-03-01 10:06:
The problem you report is a real one, but we don't completely agree
with your analysis:
* <div id='What?'>Foo</div>
id='What?' is just fine in an XHTML5 document, no matter whether XXE
supports XInclude or not.
* Yes, 'Copy as Reference' should report an error message when it
fails to create a reference out of the selection.
This bug is fixed now and 'Copy as Reference' will report an error
message in this case. However the error message will not give you much
details about what went wrong.
* With <div>Foo</div> (no id attribute) selected
'Copy as Reference' works fine if
(1) this div is the root element of the document
and/or
(2) option "Allow advanced use of XInclude" is turned on. See
http://www.xmlmind.com/xmleditor/_distrib/doc/help/editOptions.html
Otherwise 'Copy as Reference' is disabled (grayed menu entry "Edit →
Reference → Copy as Reference").
Now, we'll have to investigate to see if we can (or is legit to) make
'Copy as Reference' work even with an ID like 'What?'.
On 2/28/23 23:23, Leif H Silli wrote:
For XHTML5, the XML-based validity constraints on id attributes (that
is, on IDREFs), have been lifted. And so, since XHTML5 lacks those
constraints, XXE does not prevent us from adding the following element
to an XHTML5 document:
<div id='What?' >Foo</div>
Explanation: Questionmarks are amongst the “special characters” that
are not permitted inside id attributes of XHTML1.x documents – and
thus such characters would also not occur in id attributes, as long as
you were using a validating editor such as XXE. Hence, in the good old
days before XHTML5 was introduced, the issue I am taking up in this
message, would basically never occur.
However, provided the XXE user makes use of XInclude inclusions, the
validity constraints of XHTML1.x are as relevant as ever before.
And so, given the above fragment, if, using XXE, you select it, and
then select the command 'Copy as Reference' (from the bottom submenu
of the Edit menu), nothing happens. You do not get a warning telling
you that 'Copy as Reference' failed because the id attribute contained
characters which, from the XInclude point of view, are forbidden. The
only way to understand that it did not work, is when you paste the
reference - without getting any result.
So basically, in the above example, currently we get the same feedback
as if we tried to apply 'Copy as Reference' to the following element
(which lacks an id attribute):
<div>Foo</div>
That is: We do not get any feedback.
Proposal for a fix:
EITHER, let XXE display a 'failure' message based on a validity
conformance check of the IDREF, every time 'Copy as Reference' is used
without success. (This requires the presence of an id attribute.)
OR, let XXE simply display a general warning, every time 'Copy as
Reference' does not yield any result - even when the reason for the
“failure” is that the element lacks an id attribute.
That is, in the case of the 'OR' option, if the user tries to apply
'Copy as Reference' to an element which lacks the id attribute,
display the general warning. And also, display the same general
warning if the content of the id attribute fails to yield any result.
Example text of general warning: “No reference was copied, either
because there was no id attribute, or (if there was an id attribute)
because the content of the id attribute of the selected element [or,
if running with the 'advanced' XInclude option, of nearest parent
element] did not meet the validity constraints required by XInclude.”
I believe at least the 'OR' option should work also when XXE is
running with 'advanced XInclude' support enabled. In my case, I was
running XXE with the 'advanced' XInclude support active, when I failed
to get a result when copying the child element of a fragment. At
first I thought the issue was specific to the advanced XInclude
support, but then I came to understand that the issue is so
fundamental that it is also present in XXE's default XInclude support
mode.
Leif Halvard Silli
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