Use field formatter when exporting feature attributes to JSON

This means that field values which utilise widget setups like
value maps will correctly show the "friendly" value
for the field, instead of the raw values.

python/core/qgsjsonutils.sip

@@ -25,7 +25,7 @@ class QgsJSONExporter
 %End
   public:
 
-    QgsJSONExporter( const QgsVectorLayer *vectorLayer = 0, int precision = 6 );
+    QgsJSONExporter( QgsVectorLayer *vectorLayer = 0, int precision = 6 );
 %Docstring
  Constructor for QgsJSONExporter.
  \param vectorLayer associated vector layer (required for related attribute export)
@@ -94,7 +94,7 @@ class QgsJSONExporter
  :rtype: bool
 %End
 
-    void setVectorLayer( const QgsVectorLayer *vectorLayer );
+    void setVectorLayer( QgsVectorLayer *vectorLayer );
 %Docstring
  Sets the associated vector layer (required for related attribute export). This will automatically
  update the sourceCrs() to match.
@@ -247,10 +247,15 @@ class QgsJSONUtils
  :rtype: str
 %End
 
-    static QString exportAttributes( const QgsFeature &feature );
+    static QString exportAttributes( const QgsFeature &feature, QgsVectorLayer *layer = 0,
+                                     QVector<QVariant> attributeWidgetCaches = QVector<QVariant>() );
 %Docstring
  Exports all attributes from a QgsFeature as a JSON map type.
  \param feature feature to export
+ \param layer optional associated vector layer. If specified, this allows
+ richer export utilising settings like the layer's fields widget configuration.
+ \param attributeWidgetCaches optional widget configuration cache. Can be used
+ to speed up exporting the attributes for multiple features from the same layer.
  :rtype: str
 %End
 

src/core/qgsjsonutils.cpp

@@ -23,11 +23,13 @@
 #include "qgsproject.h"
 #include "qgscsexception.h"
 #include "qgslogger.h"
+#include "qgsfieldformatterregistry.h"
+#include "qgsfieldformatter.h"
 
 #include <QJsonDocument>
 #include <QJsonArray>
 
-QgsJSONExporter::QgsJSONExporter(QgsVectorLayer *vectorLayer, int precision )
+QgsJSONExporter::QgsJSONExporter( QgsVectorLayer *vectorLayer, int precision )
   : mPrecision( precision )
   , mIncludeGeometry( true )
   , mIncludeAttributes( true )
@@ -119,7 +121,7 @@ QString QgsJSONExporter::exportFeature( const QgsFeature &feature, const QVarian
 
     if ( mIncludeAttributes )
     {
-      QgsFields fields = feature.fields();
+      QgsFields fields = mLayer.data() ? mLayer->fields() : feature.fields();
 
       for ( int i = 0; i < fields.count(); ++i )
       {
@@ -130,6 +132,14 @@ QString QgsJSONExporter::exportFeature( const QgsFeature &feature, const QVarian
           properties += QLatin1String( ",\n" );
         QVariant val =  feature.attributes().at( i );
 
+        if ( mLayer.data() )
+        {
+          QgsEditorWidgetSetup setup = fields.at( i ).editorWidgetSetup();
+          QgsFieldFormatter *fieldFormatter = QgsApplication::fieldFormatterRegistry()->fieldFormatter( setup.type() );
+          if ( fieldFormatter != QgsApplication::fieldFormatterRegistry()->fallbackFieldFormatter() )
+            val = fieldFormatter->representValue( mLayer.data(), i, setup.config(), QVariant(), val );
+        }
+
         properties += QStringLiteral( "      \"%1\":%2" ).arg( fields.at( i ).name(), QgsJSONUtils::encodeValue( val ) );
 
         ++attributeCounter;
@@ -166,14 +176,22 @@ QString QgsJSONExporter::exportFeature( const QgsFeature &feature, const QVarian
         if ( childLayer )
         {
           QgsFeatureIterator it = childLayer->getFeatures( req );
+          QVector<QVariant> attributeWidgetCaches;
+          for ( int fieldIndex = 0; fieldIndex < childLayer->fields().count(); ++fieldIndex )
+          {
+            QgsEditorWidgetSetup setup = childLayer->fields().at( fieldIndex ).editorWidgetSetup();
+            QgsFieldFormatter *fieldFormatter = QgsApplication::fieldFormatterRegistry()->fieldFormatter( setup.type() );
+            attributeWidgetCaches.append( fieldFormatter->createCache( childLayer, fieldIndex, setup.config() ) );
+          }
+
           QgsFeature relatedFet;
           int relationFeatures = 0;
           while ( it.nextFeature( relatedFet ) )
           {
             if ( relationFeatures > 0 )
               relatedFeatureAttributes += QLatin1String( ",\n" );
 
-            relatedFeatureAttributes += QgsJSONUtils::exportAttributes( relatedFet );
+            relatedFeatureAttributes += QgsJSONUtils::exportAttributes( relatedFet, childLayer, attributeWidgetCaches );
             relationFeatures++;
           }
         }
@@ -267,7 +285,7 @@ QString QgsJSONUtils::encodeValue( const QVariant &value )
   }
 }
 
-QString QgsJSONUtils::exportAttributes( const QgsFeature &feature )
+QString QgsJSONUtils::exportAttributes( const QgsFeature &feature, QgsVectorLayer *layer, QVector<QVariant> attributeWidgetCaches )
 {
   QgsFields fields = feature.fields();
   QString attrs;
@@ -277,6 +295,15 @@ QString QgsJSONUtils::exportAttributes( const QgsFeature &feature )
       attrs += QLatin1String( ",\n" );
 
     QVariant val = feature.attributes().at( i );
+
+    if ( layer )
+    {
+      QgsEditorWidgetSetup setup = layer->fields().at( i ).editorWidgetSetup();
+      QgsFieldFormatter *fieldFormatter = QgsApplication::fieldFormatterRegistry()->fieldFormatter( setup.type() );
+      if ( fieldFormatter != QgsApplication::fieldFormatterRegistry()->fallbackFieldFormatter() )
+        val = fieldFormatter->representValue( layer, i, setup.config(), attributeWidgetCaches.count() >= i ? attributeWidgetCaches.at( i ) : QVariant(), val );
+    }
+
     attrs += encodeValue( fields.at( i ).name() ) + ':' + encodeValue( val );
   }
   return attrs.prepend( '{' ).append( '}' );

src/core/qgsjsonutils.h

@@ -240,8 +240,13 @@ class CORE_EXPORT QgsJSONUtils
 
     /** Exports all attributes from a QgsFeature as a JSON map type.
      * \param feature feature to export
+     * \param layer optional associated vector layer. If specified, this allows
+     * richer export utilising settings like the layer's fields widget configuration.
+     * \param attributeWidgetCaches optional widget configuration cache. Can be used
+     * to speed up exporting the attributes for multiple features from the same layer.
      */
-    static QString exportAttributes( const QgsFeature &feature );
+    static QString exportAttributes( const QgsFeature &feature, QgsVectorLayer *layer = nullptr,
+                                     QVector<QVariant> attributeWidgetCaches = QVector<QVariant>() );
 
     /** Parse a simple array (depth=1).
      * \param json the JSON to parse

tests/src/python/test_qgsjsonutils.py

@@ -28,7 +28,8 @@
                        QgsLineString,
                        NULL,
                        QgsVectorLayer,
-                       QgsRelation
+                       QgsRelation,
+                       QgsEditorWidgetSetup
                        )
 from qgis.PyQt.QtCore import QVariant, QTextCodec
 
@@ -145,6 +146,20 @@ def testExportAttributes(self):
 "population":198}"""
         self.assertEqual(QgsJSONUtils.exportAttributes(feature), expected)
 
+        # test using field formatters
+        source = QgsVectorLayer("Point?field=fldtxt:string&field=fldint:integer",
+                                "parent", "memory")
+        pf1 = QgsFeature()
+        pf1.setFields(source.fields())
+        pf1.setAttributes(["test1", 1])
+
+        setup = QgsEditorWidgetSetup('ValueMap', {"map": {"one": 1, "two": 2, "three": 3}})
+        source.setEditorWidgetSetup(1, setup)
+
+        expected = """{"fldtxt":"test1",
+"fldint":"one"}"""
+        self.assertEqual(QgsJSONUtils.exportAttributes(pf1, source), expected)
+
     def testJSONExporter(self):
         """ test converting features to GeoJSON """
         fields = QgsFields()
@@ -392,6 +407,38 @@ def testJSONExporter(self):
         self.assertTrue(exp_f == expected or exp_f == expected2)
         exporter.setIncludeGeometry(True)
 
+    def testExportFeatureFieldFormatter(self):
+        """ Test exporting a feature with formatting fields """
+
+        # source layer
+        source = QgsVectorLayer("Point?field=fldtxt:string&field=fldint:integer",
+                                "parent", "memory")
+        pr = source.dataProvider()
+        pf1 = QgsFeature()
+        pf1.setFields(source.fields())
+        pf1.setAttributes(["test1", 1])
+        pf2 = QgsFeature()
+        pf2.setFields(source.fields())
+        pf2.setAttributes(["test2", 2])
+        assert pr.addFeatures([pf1, pf2])
+
+        setup = QgsEditorWidgetSetup('ValueMap', {"map": {"one": 1, "two": 2, "three": 3}})
+        source.setEditorWidgetSetup(1, setup)
+
+        exporter = QgsJSONExporter()
+        exporter.setVectorLayer(source)
+
+        expected = """{
+   "type":"Feature",
+   "id":0,
+   "geometry":null,
+   "properties":{
+      "fldtxt":"test1",
+      "fldint":"one"
+   }
+}"""
+        self.assertEqual(exporter.exportFeature(pf1), expected)
+
     def testExportFeatureCrs(self):
         """ Test CRS transform when exporting features """
 
@@ -513,6 +560,27 @@ def testExportFeatureRelations(self):
 }"""
         self.assertEqual(exporter.exportFeature(pf2), expected)
 
+        # with field formatter
+        setup = QgsEditorWidgetSetup('ValueMap', {"map": {"apples": 123, "bananas": 124}})
+        child.setEditorWidgetSetup(1, setup)
+        expected = """{
+   "type":"Feature",
+   "id":0,
+   "geometry":null,
+   "properties":{
+      "fldtxt":"test1",
+      "fldint":67,
+      "foreignkey":123,
+      "relation one":[{"x":"foo",
+"y":"apples",
+"z":321},
+{"x":"bar",
+"y":"apples",
+"z":654}]
+   }
+}"""
+        self.assertEqual(exporter.exportFeature(pf1), expected)
+
         # test excluding related attributes
         exporter.setIncludeRelated(False)
         self.assertEqual(exporter.includeRelated(), False)