Merge pull request #8649 from qgis/expression_function_decode_uri

Expression function `decode_uri`

Author: m-kuhn

resources/function_help/json/decode_uri

@@ -0,0 +1,12 @@
+{
+  "name": "decode_uri",
+  "type": "function",
+  "description": "Takes a layer and decodes the uri of the underlying data provider. It depends on the dataprovider, which data is available.",
+  "arguments": [ {"arg":"layer","description":"The layer for which the uri should be decoded."},
+                 {"arg":"part","description":"The part of the uri to return. If unspecified, a map with all uri parts will be returned.","optional":true} ],
+  "examples": [ { "expression":"decode_uri(@layer)", "returns":"{'layerId': '0', 'layerName': '', 'path': '/home/qgis/shapefile.shp'}"},
+                { "expression":"decode_uri(@layer)", "returns":"{'layerId': NULL, 'layerName': 'layer', 'path': '/home/qgis/geopackage.gpkg'}"},
+                { "expression":"decode_uri(@layer, 'path')", "returns":"'C:\\\\my_data\\\\qgis\\\\shape.shp'"}
+              ]
+}
+

resources/function_help/json/layer_property

@@ -4,7 +4,7 @@
   "description": "Returns a matching layer property or metadata value.",
   "arguments": [
 	{"arg":"layer", "description":"a string, representing either a layer name or layer ID"},
-        {"arg":"property", "description":"a string corresponding to the property to return. Valid options are:<br /><ul><li>name: layer name</li><li>id: layer ID</li><li>title: metadata title string</li><li>abstract: metadata abstract string</li><li>keywords: metadata keywords</li><li>data_url: metadata URL</li><li>attribution: metadata attribution string</li><li>attribution_url: metadata attribution URL</li><li>source: layer source</li><li>min_scale: minimum display scale for layer</li><li>max_scale: maximum display scale for layer</li><li>crs: layer CRS</li><li>crs_definition: layer CRS full definition</li><li>crs_description: layer CRS description</li><li>extent: layer extent (as a geometry object)</li><li>type: layer type, e.g., Vector or Raster</li><li>storage_type: storage format (vector layers only)</li><li>geometry_type: geometry type, e.g., Point (vector layers only)</li><li>feature_count: approximate feature count for layer (vector layers only)</li></ul>"}
+        {"arg":"property", "description":"a string corresponding to the property to return. Valid options are:<br /><ul><li>name: layer name</li><li>id: layer ID</li><li>title: metadata title string</li><li>abstract: metadata abstract string</li><li>keywords: metadata keywords</li><li>data_url: metadata URL</li><li>attribution: metadata attribution string</li><li>attribution_url: metadata attribution URL</li><li>source: layer source</li><li>min_scale: minimum display scale for layer</li><li>max_scale: maximum display scale for layer</li><li>crs: layer CRS</li><li>crs_definition: layer CRS full definition</li><li>crs_description: layer CRS description</li><li>extent: layer extent (as a geometry object)</li><li>type: layer type, e.g., Vector or Raster</li><li>storage_type: storage format (vector layers only)</li><li>geometry_type: geometry type, e.g., Point (vector layers only)</li><li>feature_count: approximate feature count for layer (vector layers only)</li><li>path: File path to the layer data source. Only available for file based layers.</li></ul>"}
   ],
   "examples": [
 	{ "expression":"layer_property('streets','title')", "returns":"'Basemap Streets'"},

src/core/expression/qgsexpressionfunction.cpp

@@ -46,6 +46,7 @@
 #include "qgsfieldformatterregistry.h"
 #include "qgsfieldformatter.h"
 #include "qgsvectorlayerfeatureiterator.h"
+#include "qgsproviderregistry.h"
 
 const QString QgsExpressionFunction::helpText() const
 {
@@ -4024,12 +4025,49 @@ static QVariant fcnGetLayerProperty( const QVariantList &values, const QgsExpres
         return QgsWkbTypes::geometryDisplayString( vLayer->geometryType() );
       else if ( QString::compare( layerProperty, QStringLiteral( "feature_count" ), Qt::CaseInsensitive ) == 0 )
         return QVariant::fromValue( vLayer->featureCount() );
+      else if ( QString::compare( layerProperty, QStringLiteral( "path" ), Qt::CaseInsensitive ) == 0 )
+      {
+        if ( vLayer->dataProvider() )
+        {
+          const QVariantMap decodedUri = QgsProviderRegistry::instance()->decodeUri( layer->providerType(), layer->dataProvider()->dataSourceUri() );
+          return decodedUri.value( QStringLiteral( "path" ) );
+        }
+      }
     }
   }
 
   return QVariant();
 }
 
+static QVariant fcnDecodeUri( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  QgsMapLayer *layer = QgsExpressionUtils::getMapLayer( values.at( 0 ), parent );
+  if ( !layer )
+  {
+    parent->setEvalErrorString( QObject::tr( "Cannot find layer %1" ).arg( values.at( 0 ).toString() ) );
+    return QVariant();
+  }
+
+  if ( !layer->dataProvider() )
+  {
+    parent->setEvalErrorString( QObject::tr( "Layer %1 has invalid data provider" ).arg( layer->name() ) );
+    return QVariant();
+  }
+
+  const QString uriPart = values.at( 1 ).toString();
+
+  const QVariantMap decodedUri = QgsProviderRegistry::instance()->decodeUri( layer->providerType(), layer->dataProvider()->dataSourceUri() );
+
+  if ( !uriPart.isNull() )
+  {
+    return decodedUri.value( values.at( 1 ).toString() );
+  }
+  else
+  {
+    return decodedUri;
+  }
+}
+
 static QVariant fcnGetRasterBandStat( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
 {
   QString layerIdOrName = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
@@ -4906,6 +4944,11 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
     // **General** functions
     sFunctions
         << new QgsStaticExpressionFunction( QStringLiteral( "layer_property" ), 2, fcnGetLayerProperty, QStringLiteral( "General" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "decode_uri" ),
+                                            QgsExpressionFunction::ParameterList()
+                                            << QgsExpressionFunction::Parameter( QStringLiteral( "layer" ) )
+                                            << QgsExpressionFunction::Parameter( QStringLiteral( "part" ), true ),
+                                            fcnDecodeUri, QStringLiteral( "Map Layers" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "raster_statistic" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "layer" ) )
                                             << QgsExpressionFunction::Parameter( QStringLiteral( "band" ) )
                                             << QgsExpressionFunction::Parameter( QStringLiteral( "statistic" ) ), fcnGetRasterBandStat, QStringLiteral( "Rasters" ) );

tests/src/core/testqgsexpression.cpp

@@ -1266,6 +1266,8 @@ class TestQgsExpression: public QObject
       QTest::newRow( "layer_property storage_type" ) << QStringLiteral( "layer_property('%1','storage_type')" ).arg( mPointsLayer->name() ) << false << QVariant( "ESRI Shapefile" );
       QTest::newRow( "layer_property geometry_type" ) << QStringLiteral( "layer_property('%1','geometry_type')" ).arg( mPointsLayer->name() ) << false << QVariant( "Point" );
 
+      QTest::newRow( "decode_uri shp path" ) << QStringLiteral( "array_last(string_to_array(replace(decode_uri('%1', 'path'), '\\\\', '/'), '/'))" ).arg( mPointsLayer->name() ) << false << QVariant( "points.shp" );
+
       // raster_statistic tests
       QTest::newRow( "raster_statistic no layer" ) << "raster_statistic('',1,'min')" << false << QVariant();
       QTest::newRow( "raster_statistic bad layer" ) << "raster_statistic('bad',1,'min')" << false << QVariant();