[FEATURE] Expression functions which return file info

base_file_name: Returns the base name of the file without the directory or file suffix.
file_exists: Returns true if a file exists
file_name: Returns the file name from a full path
file_path: Returns the directory/path from a full file path
file_size: Returns a file size
file_suffix: Returns a files suffix/extension
is_directory: Returns true if a file path is a directory
is_file: Returns true if a file path is a file

resources/function_help/json/base_file_name

@@ -0,0 +1,8 @@
+{
+  "name": "base_file_name",
+  "type": "function",
+  "description": "Returns the base name of the file without the directory or file suffix.",
+  "arguments": [ {"arg":"path","description":"a file path"}],
+  "examples": [ { "expression":"base_file_name('/home/qgis/data/country_boundaries.shp')", "returns":"'country_boundaries'"}]
+}
+

resources/function_help/json/file_exists

@@ -0,0 +1,8 @@
+{
+  "name": "file_exists",
+  "type": "function",
+  "description": "Returns true if a file path exists.",
+  "arguments": [ {"arg":"path","description":"a file path"}],
+  "examples": [ { "expression":"file_exists('/home/qgis/data/country_boundaries.shp')", "returns":"true"}]
+}
+

resources/function_help/json/file_name

@@ -0,0 +1,8 @@
+{
+  "name": "file_name",
+  "type": "function",
+  "description": "Returns the name of a file (including the file extension), excluding the directory.",
+  "arguments": [ {"arg":"path","description":"a file path"}],
+  "examples": [ { "expression":"base_file_name('/home/qgis/data/country_boundaries.shp')", "returns":"'country_boundaries.shp'"}]
+}
+

resources/function_help/json/file_path

@@ -0,0 +1,8 @@
+{
+  "name": "file_path",
+  "type": "function",
+  "description": "Returns the directory component of a file path. This does not include the file name.",
+  "arguments": [ {"arg":"path","description":"a file path"}],
+  "examples": [ { "expression":"base_file_name('/home/qgis/data/country_boundaries.shp')", "returns":"'/home/qgis/data'"}]
+}
+

resources/function_help/json/file_size

@@ -0,0 +1,8 @@
+{
+  "name": "file_size",
+  "type": "function",
+  "description": "Returns the size (in bytes) of a file.",
+  "arguments": [ {"arg":"path","description":"a file path"}],
+  "examples": [ { "expression":"file_size('/home/qgis/data/country_boundaries.geojson')", "returns":"5674"}]
+}
+

resources/function_help/json/file_suffix

@@ -0,0 +1,8 @@
+{
+  "name": "file_suffix",
+  "type": "function",
+  "description": "Returns the file suffix (extension) from a file path.",
+  "arguments": [ {"arg":"path","description":"a file path"}],
+  "examples": [ { "expression":"base_file_name('/home/qgis/data/country_boundaries.shp')", "returns":"'shp'"}]
+}
+

resources/function_help/json/is_directory

@@ -0,0 +1,9 @@
+{
+  "name": "is_directory",
+  "type": "function",
+  "description": "Returns true if a path corresponds to a directory.",
+  "arguments": [ {"arg":"path","description":"a file path"}],
+  "examples": [ { "expression":"is_directory('/home/qgis/data/country_boundaries.shp')", "returns":"false"},
+{ "expression":"is_directory('/home/qgis/data/')", "returns":"true"}]
+}
+

resources/function_help/json/is_file

@@ -0,0 +1,9 @@
+{
+  "name": "is_file",
+  "type": "function",
+  "description": "Returns true if a path corresponds to a file.",
+  "arguments": [ {"arg":"path","description":"a file path"}],
+  "examples": [ { "expression":"is_file('/home/qgis/data/country_boundaries.shp')", "returns":"true"},
+{ "expression":"is_file('/home/qgis/data/')", "returns":"false"}]
+}
+

src/core/expression/qgsexpressionfunction.cpp

@@ -4782,6 +4782,57 @@ static QVariant fcnEnvVar( const QVariantList &values, const QgsExpressionContex
   return QProcessEnvironment::systemEnvironment().value( envVarName );
 }
 
+static QVariant fcnBaseFileName( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QString file = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+  return QFileInfo( file ).completeBaseName();
+}
+
+static QVariant fcnFileSuffix( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QString file = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+  return QFileInfo( file ).completeSuffix();
+}
+
+static QVariant fcnFileExists( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QString file = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+  return QFileInfo::exists( file );
+}
+
+static QVariant fcnFileName( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QString file = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+  return QFileInfo( file ).fileName();
+}
+
+static QVariant fcnPathIsFile( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QString file = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+  return QFileInfo( file ).isFile();
+}
+
+static QVariant fcnPathIsDir( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QString file = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+  return QFileInfo( file ).isDir();
+}
+
+static QVariant fcnFilePath( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QString file = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+  return QDir::toNativeSeparators( QFileInfo( file ).path() );
+}
+
+static QVariant fcnFileSize( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QString file = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+  return QFileInfo( file ).size();
+}
+
+
+
+
 const QList<QgsExpressionFunction *> &QgsExpression::Functions()
 {
   // The construction of the list isn't thread-safe, and without the mutex,
@@ -5045,6 +5096,24 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
                                             fncLighter, QStringLiteral( "Color" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "set_color_part" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "color" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "component" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "value" ) ), fncSetColorPart, QStringLiteral( "Color" ) )
 
+        // file info
+        << new QgsStaticExpressionFunction( QStringLiteral( "base_file_name" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "path" ) ),
+                                            fcnBaseFileName, QStringLiteral( "Files and Paths" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "file_suffix" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "path" ) ),
+                                            fcnFileSuffix, QStringLiteral( "Files and Paths" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "file_exists" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "path" ) ),
+                                            fcnFileExists, QStringLiteral( "Files and Paths" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "file_name" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "path" ) ),
+                                            fcnFileName, QStringLiteral( "Files and Paths" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "is_file" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "path" ) ),
+                                            fcnPathIsFile, QStringLiteral( "Files and Paths" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "is_directory" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "path" ) ),
+                                            fcnPathIsDir, QStringLiteral( "Files and Paths" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "file_path" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "path" ) ),
+                                            fcnFilePath, QStringLiteral( "Files and Paths" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "file_size" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "path" ) ),
+                                            fcnFileSize, QStringLiteral( "Files and Paths" ) )
+
         // deprecated stuff - hidden from users
         << new QgsStaticExpressionFunction( QStringLiteral( "$scale" ), QgsExpressionFunction::ParameterList(), fcnMapScale, QStringLiteral( "deprecated" ) );
 

tests/src/core/testqgsexpression.cpp

@@ -1370,9 +1370,44 @@ class TestQgsExpression: public QObject
       QTest::newRow( "array_last(array('a', 'b', 'c'))" ) << QStringLiteral( "array_last(array('a', 'b', 'c'))" ) << false << QVariant( "c" );
       QTest::newRow( "array_last(array())" ) << QStringLiteral( "array_last(array())" ) << false << QVariant();
 
-      //
+      // file functions
+      QTest::newRow( "base_file_name(5)" ) << QStringLiteral( "base_file_name(5)" ) << false << QVariant( "5" );
+      QTest::newRow( "base_file_name(NULL)" ) << QStringLiteral( "base_file_name(NULL)" ) << false << QVariant();
+      QTest::newRow( "base_file_name('/home/qgis/test.qgs')" ) << QStringLiteral( "base_file_name('/home/qgis/test.qgs')" ) << false << QVariant( "test" );
+      QTest::newRow( "base_file_name(points.shp)" ) << QStringLiteral( "base_file_name('%1/points.shp')" ).arg( TEST_DATA_DIR ) << false << QVariant( "points" );
+      QTest::newRow( "file_exists(NULL)" ) << QStringLiteral( "file_exists(NULL)" ) << false << QVariant();
+      QTest::newRow( "file_exists('/home/qgis/test.qgs')" ) << QStringLiteral( "file_exists('/home/qgis/test.qgs')" ) << false << QVariant( false );
+      QTest::newRow( "file_exists(points.shp)" ) << QStringLiteral( "file_exists('%1/points.shp')" ).arg( TEST_DATA_DIR ) << false << QVariant( true );
+      QTest::newRow( "file_name(5)" ) << QStringLiteral( "file_name(5)" ) << false << QVariant( "5" );
+      QTest::newRow( "file_name(NULL)" ) << QStringLiteral( "file_name(NULL)" ) << false << QVariant();
+      QTest::newRow( "file_name('/home/qgis/test.qgs')" ) << QStringLiteral( "file_name('/home/qgis/test.qgs')" ) << false << QVariant( "test.qgs" );
+      QTest::newRow( "file_name(points.shp)" ) << QStringLiteral( "file_name('%1/points.shp')" ).arg( TEST_DATA_DIR ) << false << QVariant( "points.shp" );
+      QTest::newRow( "file_path(5)" ) << QStringLiteral( "file_path(5)" ) << false << QVariant( "." );
+      QTest::newRow( "file_path(NULL)" ) << QStringLiteral( "file_path(NULL)" ) << false << QVariant();
+      QTest::newRow( "file_path('/home/qgis/test.qgs')" ) << QStringLiteral( "file_path('/home/qgis/test.qgs')" ) << false << QVariant( "/home/qgis" );
+      QTest::newRow( "file_path(points.shp)" ) << QStringLiteral( "file_path('%1/points.shp')" ).arg( TEST_DATA_DIR ) << false << QVariant( TEST_DATA_DIR );
+      QTest::newRow( "file_size(5)" ) << QStringLiteral( "file_size(5)" ) << false << QVariant( 0LL );
+      QTest::newRow( "file_size(NULL)" ) << QStringLiteral( "file_size(NULL)" ) << false << QVariant();
+      QTest::newRow( "file_size('/home/qgis/test.qgs')" ) << QStringLiteral( "file_size('/home/qgis/test.qgs')" ) << false << QVariant( 0LL );
+      QTest::newRow( "file_size(points.shp)" ) << QStringLiteral( "file_size('%1/points.shp')" ).arg( TEST_DATA_DIR ) << false << QVariant( 576LL );
+      QTest::newRow( "file_suffix(5)" ) << QStringLiteral( "file_suffix(5)" ) << false << QVariant( "" );
+      QTest::newRow( "file_suffix(NULL)" ) << QStringLiteral( "file_suffix(NULL)" ) << false << QVariant();
+      QTest::newRow( "file_suffix('/home/qgis/test.qgs')" ) << QStringLiteral( "file_suffix('/home/qgis/test.qgs')" ) << false << QVariant( "qgs" );
+      QTest::newRow( "file_suffix(points.shp)" ) << QStringLiteral( "file_suffix('%1/points.shp')" ).arg( TEST_DATA_DIR ) << false << QVariant( "shp" );
+      QTest::newRow( "is_directory(5)" ) << QStringLiteral( "is_directory(5)" ) << false << QVariant( false );
+      QTest::newRow( "is_directory(NULL)" ) << QStringLiteral( "is_directory(NULL)" ) << false << QVariant();
+      QTest::newRow( "is_directory('/home/qgis/test.qgs')" ) << QStringLiteral( "is_directory('/home/qgis/test.qgs')" ) << false << QVariant( false );
+      QTest::newRow( "is_directory(points.shp)" ) << QStringLiteral( "is_directory('%1/points.shp')" ).arg( TEST_DATA_DIR ) << false << QVariant( false );
+      QTest::newRow( "is_directory(valid)" ) << QStringLiteral( "is_directory('%1')" ).arg( TEST_DATA_DIR ) << false << QVariant( true );
+      QTest::newRow( "is_file(5)" ) << QStringLiteral( "is_file(5)" ) << false << QVariant( false );
+      QTest::newRow( "is_file(NULL)" ) << QStringLiteral( "is_file(NULL)" ) << false << QVariant();
+      QTest::newRow( "is_file('/home/qgis/test.qgs')" ) << QStringLiteral( "is_file('/home/qgis/test.qgs')" ) << false << QVariant( false );
+      QTest::newRow( "is_file(points.shp)" ) << QStringLiteral( "is_file('%1/points.shp')" ).arg( TEST_DATA_DIR ) << false << QVariant( true );
+      QTest::newRow( "is_file(valid)" ) << QStringLiteral( "is_file('%1')" ).arg( TEST_DATA_DIR ) << false << QVariant( false );
+
     }
 
+
     void run_evaluation_test( QgsExpression &exp, bool evalError, QVariant &expected )
     {
       if ( exp.hasParserError() )