[processing] Fix exception when calling "Select from Files" in batch …

…mode

on a file parameter

Fixes #40705

python/core/auto_generated/processing/qgsprocessingparameters.sip.in

@@ -1743,7 +1743,7 @@ Creates a new parameter using the definition from a script code.
 
 };
 
-class QgsProcessingParameterFile : QgsProcessingParameterDefinition
+class QgsProcessingParameterFile : QgsProcessingParameterDefinition, QgsFileFilterGenerator
 {
 %Docstring
 An input file or folder parameter for processing algorithms.
@@ -1785,6 +1785,8 @@ Returns the type name for the parameter class.
 
     virtual QString asPythonString( QgsProcessing::PythonOutputType outputType = QgsProcessing::PythonQgsProcessingAlgorithmSubclass ) const;
 
+    virtual QString createFileFilter() const;
+
 
     Behavior behavior() const;
 %Docstring

python/plugins/processing/gui/BatchPanel.py

@@ -81,7 +81,8 @@
     QgsProcessing,
     QgsExpression,
     QgsRasterLayer,
-    QgsProcessingUtils
+    QgsProcessingUtils,
+    QgsFileFilterGenerator
 )
 from qgis.gui import (
     QgsProcessingParameterWidgetContext,
@@ -152,13 +153,7 @@ def createMenu(self):
         add_by_expression.setToolTip(self.tr('Adds new parameter values by evaluating an expression'))
         self.menu.addAction(add_by_expression)
 
-        if isinstance(self.parameterDefinition, (QgsProcessingParameterFile,
-                                                 QgsProcessingParameterMapLayer,
-                                                 QgsProcessingParameterRasterLayer,
-                                                 QgsProcessingParameterMeshLayer,
-                                                 QgsProcessingParameterVectorLayer,
-                                                 QgsProcessingParameterFeatureSource,
-                                                 QgsProcessingParameterMultipleLayers)):
+        if not self.parameterDefinition.isDestination() and isinstance(self.parameterDefinition, QgsFileFilterGenerator):
             self.menu.addSeparator()
             find_by_pattern_action = QAction(QCoreApplication.translate('BatchPanel', 'Add Files by Pattern…'),
                                              self.menu)

src/core/processing/qgsprocessingparameters.cpp

@@ -3385,6 +3385,26 @@ QString QgsProcessingParameterFile::asPythonString( const QgsProcessing::PythonO
   return QString();
 }
 
+QString QgsProcessingParameterFile::createFileFilter() const
+{
+  switch ( mBehavior )
+  {
+    case File:
+    {
+      if ( !mFileFilter.isEmpty() )
+        return mFileFilter != QObject::tr( "All files (*.*)" ) ? mFileFilter + QStringLiteral( ";;" ) + QObject::tr( "All files (*.*)" ) : mFileFilter;
+      else if ( !mExtension.isEmpty() )
+        return QObject::tr( "%1 files" ).arg( mExtension.toUpper() ) + QStringLiteral( " (*." ) + mExtension.toLower() +  QStringLiteral( ");;" ) + QObject::tr( "All files (*.*)" );
+      else
+        return QObject::tr( "All files (*.*)" );
+    }
+
+    case Folder:
+      return QString();
+  }
+  return QString();
+}
+
 void QgsProcessingParameterFile::setExtension( const QString &extension )
 {
   mExtension = extension;

src/core/processing/qgsprocessingparameters.h

@@ -1772,7 +1772,7 @@ class CORE_EXPORT QgsProcessingParameterGeometry : public QgsProcessingParameter
  * An input file or folder parameter for processing algorithms.
   * \since QGIS 3.0
  */
-class CORE_EXPORT QgsProcessingParameterFile : public QgsProcessingParameterDefinition
+class CORE_EXPORT QgsProcessingParameterFile : public QgsProcessingParameterDefinition, public QgsFileFilterGenerator
 {
   public:
 
@@ -1802,6 +1802,7 @@ class CORE_EXPORT QgsProcessingParameterFile : public QgsProcessingParameterDefi
     bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = nullptr ) const override;
     QString asScriptCode() const override;
     QString asPythonString( QgsProcessing::PythonOutputType outputType = QgsProcessing::PythonQgsProcessingAlgorithmSubclass ) const override;
+    QString createFileFilter() const override;
 
     /**
      * Returns the parameter behavior (e.g. File or Folder).

tests/src/analysis/testqgsprocessing.cpp

@@ -3736,6 +3736,19 @@ void TestQgsProcessing::parameterFile()
   QCOMPARE( fromCode->flags(), def->flags() );
   QCOMPARE( fromCode->defaultValue(), def->defaultValue() );
   QCOMPARE( fromCode->behavior(), def->behavior() );
+
+  // create file filter
+  // folder type
+  QCOMPARE( def->createFileFilter(), QString() );
+  def.reset( new QgsProcessingParameterFile( "optional", QString(), QgsProcessingParameterFile::File, QString(), QString( "/home/me" ),  true ) );
+  // no filter/extension
+  QCOMPARE( def->createFileFilter(), QStringLiteral( "All files (*.*)" ) );
+  def->setExtension( QStringLiteral( "png" ) );
+  QCOMPARE( def->createFileFilter(), QStringLiteral( "PNG files (*.png);;All files (*.*)" ) );
+  def->setFileFilter( QStringLiteral( "PNG Files (*.png);;BMP Files (*.bmp)" ) );
+  QCOMPARE( def->createFileFilter(), QStringLiteral( "PNG Files (*.png);;BMP Files (*.bmp);;All files (*.*)" ) );
+  def->setFileFilter( QStringLiteral( "All files (*.*)" ) );
+  QCOMPARE( def->createFileFilter(), QStringLiteral( "All files (*.*)" ) );
 }
 
 void TestQgsProcessing::parameterMatrix()