Re: xml.el: xml-get-attribute returns "" if not found

[Mark A. Hershberger]

Juri Linkov <address@hidden> writes:

> Magnus Henoch <address@hidden> writes:
>> In lisp/xml.el, the function xml-get-attribute returns "" if the requested
>> attribute does not exist.  To me it seems that returning nil would make
>> more sense in that case.
>
> Please, install this patch.  The current function don't disambiguate
> between cases when XML attribute has an empty string as its value and
> when there are no such attribute at all.  This patch correctly fixes
> this.

Someone mentioned that Magnus would have to papers on file to apply
the patch.

Here is a similar patch with equivalent functionality that I
created.  Since I have papers on file, perhaps this one could be
applied?

2003-11-24  Mark A. Hershberger  <address@hidden>

        * xml.el (xml-get-attribute-or-nil): New function.  Disambiguate
        between an non-existant attribute and an empty attribute.

-(defun xml-get-attribute (node attribute)
-  "Get from NODE the value of ATTRIBUTE.
-An empty string is returned if the attribute was not found."
-  (if (xml-node-attributes node)
+(defun xml-get-attribute-or-nil (node attribute)
+  "Get the value of ATTRIBUTE from NODE.
+Returns nil if the attribute is not found.
+
+See also `xml-get-attribute'"
+  (when (xml-node-attributes node)
       (let ((value (assoc attribute (xml-node-attributes node))))
-       (if value
-           (cdr value)
-         ""))
-    ""))
+       (when value
+           (cdr value)))))
+
+(defsubst xml-get-attribute (node attribute)
+  "Get the the value of ATTRIBUTE from NODE.
+Returns an empty string if the attribute is not found.
+
+See also `xml-get-attribute-or-nil'"
+  (or (xml-get-attribute-or-nil node attribute) ""))
 
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