Description
What is the problem
When used inside a predicate, the self:: axis throws error XPST0005 in some cirumstances, even though nothing is wrong with the expression. This happens with the most recent eXist releases 4.5.0 and 5.0.0-RC5 (and earlier releases).
What did you expect
I would expect the query to run without errors (confirmed with Saxon).
Describe how to reproduce or add a test
Behaviour is the same for in-memory and stored nodes, so these stand-alone test cases will illustrate the problem.
[1]
let $node :=
<test>
<el>test <el1>test</el1> test <el2>test</el2></el>
</test>
return
$node/el[self::el1]
This should return an empty result set. Instead following error is being thrown:
org.xmldb.api.base.XMLDBException: exerr:ERROR err:XPST0005 Self::{}el1 called on set of nodes which do not contain any nodes of this name. [at line 5, column 23, source: let $node :=
<test>
<el>test <el1>test</el1> test <el2>test</el2></el>
</test>
return $node/el[self::el1]] [at line 5, column 23]
at org.exist.xmldb.RemoteXPathQueryService.compile(RemoteXPathQueryService.java:130)
at org.exist.client.QueryDialog$QueryThread.run(QueryDialog.java:558)
Caused by: org.exist.xquery.XPathException: exerr:ERROR err:XPST0005 Self::{}el1 called on set of nodes which do not contain any nodes of this name. [at line 5, column 23, source: let $node :=
<test>
<el>test <el1>test</el1> test <el2>test</el2></el>
</test>
return $node/el[self::el1]] [at line 5, column 23]
at org.exist.xmldb.RemoteXPathQueryService.throwXPathException(RemoteXPathQueryService.java:179)
at org.exist.xmldb.RemoteXPathQueryService.compileAndCheck(RemoteXPathQueryService.java:155)
at org.exist.xmldb.RemoteXPathQueryService.compile(RemoteXPathQueryService.java:128)
... 1 more
Caused by: org.exist.xquery.XPathException: exerr:ERROR err:XPST0005 Self::{}el1 called on set of nodes which do not contain any nodes of this name. [at line 5, column 23, source: let $node :=
<test>
<el>test <el1>test</el1> test <el2>test</el2></el>
</test>
return $node/el[self::el1]] [at line 5, column 23]
at org.exist.xmldb.RemoteXPathQueryService.throwXPathException(RemoteXPathQueryService.java:179)
at org.exist.xmldb.RemoteXPathQueryService.compileAndCheck(RemoteXPathQueryService.java:155)
at org.exist.xmldb.RemoteXPathQueryService.compile(RemoteXPathQueryService.java:128)
at org.exist.client.QueryDialog$QueryThread.run(QueryDialog.java:558)
Of course, this example is contrived, in order to present a simple test case. It seems, however, that the empty node set returned by the test condition in the predicate is significant. If the self:: axis does select a node (e.g. $node/el[self::el]), the query does run without error.
[2]
I've found another failing variant XQuery where the self:: axis occurs inside a predicate and doesn't select a node. Here, parentheses seem to be triggering the same error:
let $node :=
<test>
<el>test <el1>test</el1> test <el2>test</el2></el>
</test>
return $node/el[descendant::*/(self::el1)]
This should return the node:
<el>test <el1>test</el1> test <el2>test</el2></el>
Instead, above error XPST0005 is being thrown.
Here, the parentheses seem to be crucial. Compare with the same predicate without parentheses:
let $node :=
<test>
<el>test <el1>test</el1> test <el2>test</el2></el>
</test>
return $node/el[descendant::*/self::el1]
...which does return the correct result:
<el>test <el1>test</el1> test <el2>test</el2></el>
I've found a reference to this error message in the ML archives (https://sourceforge.net/p/exist/mailman/message/32496312/), and a bug fix in Github. So there's a chance this issue is related to #249.
Context information
Please always add the following information