QGISserver WFS returns invalid GML in case of cascading WFS

[rduivenvoorde]

As reported in the user mailing list:
https://lists.osgeo.org/pipermail/qgis-user/2021-February/047880.html

it looks like QGIS WFS server does not return valid GML in case of a cascading WFS.
I think it tries to add a 'namespace' to the featuremember xml elements, while there IS already a 'namespace'.

See below: the <qgs:test:provincies gml:id="test:provincies.3"> parts.

<gml:featureMember>
 <qgs:test:provincies gml:id="test:provincies.3">
  <gml:boundedBy>
   <gml:Envelope srsName="EPSG:28992">
    <gml:lowerCorner>72132.8 359038.7</gml:lowerCorner>
    <gml:upperCorner>200852 426854.1</gml:upperCorner>
   </gml:Envelope>
  </gml:boundedBy>
  <qgs:geometry>
   <MultiPolygon xmlns="http://www.opengis.net/gml" srsName="EPSG:28992">
    <polygonMember xmlns="http://www.opengis.net/gml">
     <Polygon xmlns="http://www.opengis.net/gml">
      <exterior xmlns="http://www.opengis.net/gml">
       <LinearRing xmlns="http://www.opengis.net/gml">
        <posList xmlns="http://www.opengis.net/gml" srsDimension="2">200191.5 399580.1 200258.9 399250.3 200144.6 398823.5 200090 398221 200188 397887.5 200345.8 397471.3 200590 397074.4 200852 396850.7 200731.2 396765.2 200604 396884.7 200499.7 396829.7 200563.4 396699.9 200317.9 396630.7 200086.5 396746.2 199758.4>
       </LinearRing>
      </exterior>
     </Polygon>
    </polygonMember>
   </MultiPolygon>
  </qgs:geometry>
  <qgs:fid>11</qgs:fid>
  <qgs:PROVC>30</qgs:PROVC>
  <qgs:PROVC_NM>Noord-Brabant</qgs:PROVC_NM>
  <qgs:INW_T>2373569</qgs:INW_T>
 </qgs:test:provincies>
</gml:featureMember>
<gml:featureMember>

Attached: test.gml.zip is the return data from QGISserver.

To reproduce:

• create a simple Geoserver layer (I downloaded 2.18.2) and serv it as WFS, I put it in a namespace 'test' can the layer was named 'provincies)
• create a QGIS project with only THAT wfs layer, make sure you add it to serve it in the layer props
• use that project as a project file for QGISserver WFS (I just used qgis_mapsever in output directory)
• create a QGIS project and connect to the running QGISserver
• note that it rightfully shows the layers
• note that it returns the layer as WM(!)S fine
• note that it it returns an error whey you try to show it as WFS

By looking in the debug window of QGISserver, copy/pasting the url and saving the response as test.gml I was able to save the attached test.gml.zip

Also note the

```ogrinfo test.gml`` works and shows:

$ ogrinfo test.gml
INFO: Open of `test.gml'
      using driver `GML' successful.
1: test:provincies (Multi Polygon)

But $ ogrinfo -al test.gml ONLY returns the bbox info (and NOT the features):

$ ogrinfo -al test.gml
INFO: Open of `test.gml'
      using driver `GML' successful.

Layer name: test:provincies
Geometry: Multi Polygon
Feature Count: 0
Extent: (61331.730481, 324068.944790) - (218326.962960, 413496.608860)
Layer SRS WKT:
PROJCRS["Amersfoort / RD New",
    BASEGEOGCRS["Amersfoort",
        DATUM["Amersfoort",
            ELLIPSOID["Bessel 1841",6377397.155,299.1528128,
                LENGTHUNIT["metre",1]]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433]],
        ID["EPSG",4289]],
    CONVERSION["RD New",
        METHOD["Oblique Stereographic",
            ID["EPSG",9809]],
        PARAMETER["Latitude of natural origin",52.1561605555556,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8801]],
        PARAMETER["Longitude of natural origin",5.38763888888889,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8802]],
        PARAMETER["Scale factor at natural origin",0.9999079,
            SCALEUNIT["unity",1],
            ID["EPSG",8805]],
        PARAMETER["False easting",155000,
            LENGTHUNIT["metre",1],
            ID["EPSG",8806]],
        PARAMETER["False northing",463000,
            LENGTHUNIT["metre",1],
            ID["EPSG",8807]]],
    CS[Cartesian,2],
        AXIS["easting (X)",east,
            ORDER[1],
            LENGTHUNIT["metre",1]],
        AXIS["northing (Y)",north,
            ORDER[2],
            LENGTHUNIT["metre",1]],
    USAGE[
        SCOPE["Engineering survey, topographic mapping."],
        AREA["Netherlands - onshore, including Waddenzee, Dutch Wadden Islands and 12-mile offshore coastal zone."],
        BBOX[50.75,3.2,53.7,7.22]],
    ID["EPSG",28992]]
Data axis to CRS axis mapping: 1,2
Geometry Column = geometry
gml_id: String (0.0) NOT NULL
fid: Integer64 (0.0)
PROVC: Integer64 (0.0)
PROVC_NM: String (0.0)
INW_T: Integer64 (0.0)

[frippe12573]

waiting for the built release, this solution/workaround worked to me: [https://github.com//issues/25847]

[rduivenvoorde]

@elpaso just wondering: should you really replace the ':' with a '-'?

Because you are rewriting the schema of the xml in that way. While I think if you cascade a WFS I would have hoped that I just receive the same gml as I would receive from the original WFS.
In the way it is handled in your PR for example, I cannot use the same filters because the element namespace/names have in changed.

Would it not be better to ONLY add a qgs-namespace if there is NO namespace? And IF there is a namespace, leave it as is?

In that way applications which count on a xml schema would still work?