feature picker model: correctly initalize fields for invalid feature

and force it to be valid in the expression preview widget, so expression can be evaluated even when layer has no feature fixes #37100
qgis · Jun 11, 2020 · e4987fd · e4987fd
1 parent bf04e38
commit e4987fd
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Showing 5 changed files with 21 additions and 10 deletions.
diff --git a/src/core/qgsfeatureexpressionvaluesgatherer.h b/src/core/qgsfeatureexpressionvaluesgatherer.h
@@ -68,10 +68,10 @@ class QgsFeatureExpressionValuesGatherer: public QThread
         , feature( _feature )
       {}
 
-      Entry( const QgsFeatureId &_featureId, const QString &_value )
+      Entry( const QgsFeatureId &_featureId, const QString &_value, const QgsVectorLayer *layer )
         : featureId( _featureId )
         , value( _value )
-        , feature( QgsFeature() )
+        , feature( QgsFeature( layer->fields() ) )
       {}
 
       QVariantList identifierFields;
@@ -82,9 +82,9 @@ class QgsFeatureExpressionValuesGatherer: public QThread
       bool operator()( const Entry &lhs, const Entry &rhs ) const;
     };
 
-    static Entry nullEntry()
+    static Entry nullEntry( QgsVectorLayer *layer )
     {
-      return Entry( QVariantList(), QgsApplication::nullRepresentation(), QgsFeature() );
+      return Entry( QVariantList(), QgsApplication::nullRepresentation(), QgsFeature( layer->fields() ) );
     }
 
     void run() override

diff --git a/src/core/qgsfeaturefiltermodel.cpp b/src/core/qgsfeaturefiltermodel.cpp
@@ -83,7 +83,7 @@ QgsFeatureExpressionValuesGatherer::Entry QgsFeatureFilterModel::createEntry( co
   for ( const QVariant &v : constValues )
     values << QStringLiteral( "(%1)" ).arg( v.toString() );
 
-  return QgsFeatureExpressionValuesGatherer::Entry( constValues, values.join( QStringLiteral( " " ) ), QgsFeature() );
+  return QgsFeatureExpressionValuesGatherer::Entry( constValues, values.join( QStringLiteral( " " ) ), QgsFeature( sourceLayer()->fields() ) );
 }
 
 bool QgsFeatureFilterModel::compareEntries( const QgsFeatureExpressionValuesGatherer::Entry &a, const QgsFeatureExpressionValuesGatherer::Entry &b ) const

diff --git a/src/core/qgsfeaturepickermodel.cpp b/src/core/qgsfeaturepickermodel.cpp
@@ -27,7 +27,7 @@ QgsFeaturePickerModel::QgsFeaturePickerModel( QObject *parent )
   setFetchGeometry( true );
   setExtraIdentifierValueUnguarded( nullIentifier() );
 
-  connect( this, &QgsFeaturePickerModelBase::extraIdentifierValueIndexChanged, this, [ = ]() {emit featureChanged( feature() );} );
+  connect( this, &QgsFeaturePickerModelBase::extraIdentifierValueIndexChanged, this, [ = ]() {emit featureChanged( QgsFeature( sourceLayer()->fields() ) );} );
 }
 
 void QgsFeaturePickerModel::requestToReloadCurrentFeature( QgsFeatureRequest &request )
@@ -43,7 +43,7 @@ QVariant QgsFeaturePickerModel::entryIdentifier( const QgsFeatureExpressionValue
 QgsFeatureExpressionValuesGatherer::Entry QgsFeaturePickerModel::createEntry( const QVariant &identifier ) const
 {
   QgsFeatureId fid = identifier.value<QgsFeatureId>();
-  return QgsFeatureExpressionValuesGatherer::Entry( fid, QStringLiteral( "(%1)" ).arg( fid ) );
+  return QgsFeatureExpressionValuesGatherer::Entry( fid, QStringLiteral( "(%1)" ).arg( fid ), sourceLayer() );
 }
 
 bool QgsFeaturePickerModel::compareEntries( const QgsFeatureExpressionValuesGatherer::Entry &a, const QgsFeatureExpressionValuesGatherer::Entry &b ) const

diff --git a/src/core/qgsfeaturepickermodelbase.cpp b/src/core/qgsfeaturepickermodelbase.cpp
@@ -263,7 +263,7 @@ void QgsFeaturePickerModelBase::updateCompleter()
 
     if ( mAllowNull )
     {
-      entries.prepend( QgsFeatureExpressionValuesGatherer::nullEntry() );
+      entries.prepend( QgsFeatureExpressionValuesGatherer::nullEntry( mSourceLayer ) );
     }
 
     const int newEntriesSize = entries.size();
@@ -497,7 +497,7 @@ void QgsFeaturePickerModelBase::setExtraIdentifierValueUnguarded( const QVariant
       }
       else
       {
-        mEntries.prepend( QgsFeatureExpressionValuesGatherer::nullEntry() );
+        mEntries.prepend( QgsFeatureExpressionValuesGatherer::nullEntry( mSourceLayer ) );
       }
       endInsertRows();
 

diff --git a/src/gui/qgsexpressionpreviewwidget.cpp b/src/gui/qgsexpressionpreviewwidget.cpp
@@ -48,7 +48,18 @@ void QgsExpressionPreviewWidget::setExpressionText( const QString &expression )
 void QgsExpressionPreviewWidget::setCurrentFeature( const QgsFeature &feature )
 {
   // todo: update the combo box if it has been set externaly?
-  mExpressionContext.setFeature( feature );
+
+  // force the feature to be valid, so it can evaluate an invalid feature but having its fields set
+  if ( !feature.isValid() )
+  {
+    QgsFeature validFeature( feature );
+    validFeature.setValid( true );
+    mExpressionContext.setFeature( validFeature );
+  }
+  else
+  {
+    mExpressionContext.setFeature( feature );
+  }
   refreshPreview();
 }