Don't append feature prefix twice in WFS requests

Some WFS servers like tinyOWS require the feature prefix to be in the
feature type for the feature to be found (eg `prefix:layer`).

The problem was, the prefix was always added to the feature type which
gave us a type name like `prefix:prefix:feature` or
`feature:prefix:feature`. The requests were then rejected by the WFS
server.

We now check if the feature type starts with the prefix. If it does, we
don't append it again. If it doesn't we do.

src/ol/format/wfs.js

@@ -392,10 +392,9 @@ ol.format.WFS.writeDelete_ = function(node, feature, objectStack) {
   ol.asserts.assert(feature.getId() !== undefined, 26); // Features must have an id set
   var featureType = context['featureType'];
   var featurePrefix = context['featurePrefix'];
-  featurePrefix = featurePrefix ? featurePrefix :
-      ol.format.WFS.FEATURE_PREFIX;
   var featureNS = context['featureNS'];
-  node.setAttribute('typeName', featurePrefix + ':' + featureType);
+  var typeName = ol.format.WFS.getTypeName_(featurePrefix, featureType);
+  node.setAttribute('typeName', typeName);
   ol.xml.setAttributeNS(node, ol.format.WFS.XMLNS, 'xmlns:' + featurePrefix,
       featureNS);
   var fid = feature.getId();
@@ -405,6 +404,25 @@ ol.format.WFS.writeDelete_ = function(node, feature, objectStack) {
 };
 
 
+/**
+ * @param {string|undefined} featurePrefix The prefix of the feature.
+ * @param {string} featureType The type of the feature.
+ * @returns {string} The value of the typeName property.
+ * @private
+ */
+ol.format.WFS.getTypeName_ = function(featurePrefix, featureType) {
+  featurePrefix = featurePrefix ? featurePrefix :
+      ol.format.WFS.FEATURE_PREFIX;
+  var prefix = featurePrefix + ':';
+  // The featureType already contains the prefix.
+  if (featureType.indexOf(prefix) === 0) {
+    return featureType;
+  } else {
+    return prefix + featureType;
+  }
+};
+
+
 /**
  * @param {Node} node Node.
  * @param {ol.Feature} feature Feature.
@@ -416,10 +434,9 @@ ol.format.WFS.writeUpdate_ = function(node, feature, objectStack) {
   ol.asserts.assert(feature.getId() !== undefined, 27); // Features must have an id set
   var featureType = context['featureType'];
   var featurePrefix = context['featurePrefix'];
-  featurePrefix = featurePrefix ? featurePrefix :
-      ol.format.WFS.FEATURE_PREFIX;
   var featureNS = context['featureNS'];
-  node.setAttribute('typeName', featurePrefix + ':' + featureType);
+  var typeName = ol.format.WFS.getTypeName_(featurePrefix, featureType);
+  node.setAttribute('typeName', typeName);
   ol.xml.setAttributeNS(node, ol.format.WFS.XMLNS, 'xmlns:' + featurePrefix,
       featureNS);
   var fid = feature.getId();
@@ -512,8 +529,14 @@ ol.format.WFS.writeQuery_ = function(node, featureType, objectStack) {
   var featureNS = context['featureNS'];
   var propertyNames = context['propertyNames'];
   var srsName = context['srsName'];
-  var prefix = featurePrefix ? featurePrefix + ':' : '';
-  node.setAttribute('typeName', prefix + featureType);
+  var typeName;
+  // If feature prefix is not defined, we must not use the default prefix.
+  if (featurePrefix) {
+    typeName = ol.format.WFS.getTypeName_(featurePrefix, featureType);
+  } else {
+    typeName = featureType;
+  }
+  node.setAttribute('typeName', typeName);
   if (srsName) {
     node.setAttribute('srsName', srsName);
   }