Validate XML Schema with Xerces XSD validator.

[angelozerr]

See #190

Signed-off-by: azerr [email protected]

[angelozerr]

@fbricon @NikolasKomonen if you wish to play with XSD validator you can use XSD files https://github.com/angelozerr/lsp4xml/tree/xsdvalidator/org.eclipse.lsp4xml/src/test/resources/validation/schema

[angelozerr]

Please note that I tested with JDK 11 and it works (test was done with JDK 11 because I'm using Java Reflection because Xerces cannot work with reporter (only error handler) for XSD validator)

[fbricon]

Error ranges are off

using:

<?xml version='1.0'?>
<xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema'>
    <xs:element name='note'>
        <xs:complexType>
            <xs:sequence>
                <xs:element nhame='to' type='xs:string' nillable='false' />
                <xs:element name='from' type='xs:string' />
                <xs:element name='heading' type='xs:string' />
                <xs:element name='body' type='xs:string' nillable='false' />
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

[angelozerr]

Error ranges are off

Error ranges was implemented like WTP XML Editor, but there are some error ranges which ar emissing like you have found. I hav eimplemented it but we need other error I think. Perhaps it could be an another PR?

[NikolasKomonen]

Works well for me, and if any error ranges were missed we can create new issues for them.