[xml] No warnings if xsd:import files not found

[Brian Candler <b candler pobox com>]

Hi,

It seems xmllint doesn't give any notification if it's unable to load a 
file referenced in an xsd:import, and I wondered if this was 
intentional, because it just carries on blindly and this results in 
confusing errors.

For example, I'm testing under OSX using the schema and examples in this 
file:

http://www.niccstandards.org.uk/files/current/nd1641v1.1.1.zip?type=zip

After unzipping this, I'm doing:

$ xmllint --noout --schema Schemas/NICC-common/NICC-Fulfilment-v1-0.xsd 
L2C/Examples/OrderStatusUpdate\ -\ EUAC\ -\ Provide\ -\ KCI1.xml

which gives a bunch of errors starting with:

Schemas/NICC-common/NICC-Fulfilment-v1-0.xsd:59: element element: 
Schemas parser error : Element 
'{http://www.w3.org/2001/XMLSchema}element', attribute 'ref': The QName 
value '{urn:uk.org.NICC/tML/Fulfilment/NICC-Order-v1-0}Order' does not 
resolve to a(n) element declaration.
Schemas/NICC-common/NICC-Fulfilment-v1-0.xsd:65: element element: 
Schemas parser error : Element 
'{http://www.w3.org/2001/XMLSchema}element', attribute 'ref': The QName 
value 
'{urn:uk.org.NICC/tML/Fulfilment/NICC-OrderAmendment-v1-0}OrderAmendment' does 
not resolve to a(n) element declaration.
... snip many more ...

Now, Schemas/NICC-common/NICC-Fulfilment-v1-0.xsd contains the following:

        <xsd:import 
namespace="urn:uk.org.NICC/tML/Fulfilment/NICC-Order-v1-0" 
schemaLocation="..\maindoc\NICC-Order-v1-0.xsd"/>
...
        <xsd:complexType name="AddOrder">
                <xsd:sequence>
                        <xsd:element ref="ord:Order"/> <<<< this is 
what fails
                </xsd:sequence>
        </xsd:complexType>

and Order is defined in NICC-Order-v1-0.xsd

You can see that the xsd:import uses a relative path with Windows-style 
backslash path separators. If I change all the backslashes to forward 
slashes, lo and behold, the file validates!

$ xmllint --noout --schema Schemas2/NICC-common/NICC-Fulfilment-v1-0.xsd 
L2C/Examples/OrderStatusUpdate\ -\ EUAC\ -\ Provide\ -\ KCI1.xml
L2C/Examples/OrderStatusUpdate - EUAC - Provide - KCI1.xml validates

But this would have been much easier to debug if xmllint had given at 
least a warning that it had tried to locate a file to import, and failed.

Adding --debug or --debugent doesn't provide such a warning.  Adding 
--load-trace shows only

Loaded URL="Schemas/NICC-common/NICC-Fulfilment-v1-0.xsd" ID="(null)"

but gives no indication that it attempted to load any other file. Once I 
fix the slashes, I can see it loading all the schema files:

Loaded URL="Schemas2/NICC-common/NICC-Fulfilment-v1-0.xsd" ID="(null)"
Loaded URL="Schemas2/maindoc/NICC-Order-v1-0.xsd" ID="(null)"
Loaded 
URL="Schemas2/NICC-common/NICC-CommonAggregateComponents-v1-0.xsd" 
ID="(null)"
... etc

Am I missing something? Is there a flag to get a warning on failed imports?

Thanks,

Brian Candler.

P.S. This was tested with the xmllint included in OSX 10.9.5, and also 
2.9.1 compiled using homebrew.

$ xmllint --version
xmllint: using libxml version 20900
   compiled with: Threads Tree Output Push Reader Patterns Writer SAXv1 
FTP HTTP DTDValid HTML Legacy C14N Catalog XPath XPointer XInclude 
ISO8859X Unicode Regexps Automata Expr Schemas Schematron Modules Debug Zlib
$ /usr/local/Cellar/libxml2/2.9.1/bin/xmllint --version
/usr/local/Cellar/libxml2/2.9.1/bin/xmllint: using libxml version 20901
   compiled with: Threads Tree Output Push Reader Patterns Writer SAXv1 
FTP HTTP DTDValid HTML Legacy C14N Catalog XPath XPointer XInclude Iconv 
ISO8859X Unicode Regexps Automata Expr Schemas Schematron Modules Debug Zlib