Allow setting a custom path pre-processor for QgsPathResolver

python/core/auto_generated/qgspathresolver.sip.in

@@ -9,7 +9,6 @@
 
 
 
-
 class QgsPathResolver
 {
 %Docstring
@@ -39,6 +38,75 @@ Paths written to the project file should be prepared with this method.
 Turn filename read from the project file to an absolute path
 %End
 
+
+    static void setPathPreprocessor( SIP_PYCALLABLE / AllowNone / );
+%Docstring
+Sets a path pre-processor function, which allows for manipulation of paths and data sources prior
+to resolving them to file references or layer sources.
+
+The ``processor`` function must accept a single string argument (representing the original file path
+or data source), and return a processed version of this path.
+
+The path pre-processor function is called before any bad layer handler.
+
+.. note::
+
+   Setting a new ``processor`` replaces any existing processor.
+
+Example - replace an outdated folder path with a new one:
+.. code-block:: python
+
+       def my_processor(path):
+          return path.replace('c:/Users/ClintBarton/Documents/Projects', 'x:/Projects/')
+
+       QgsPathResolver.setPathPreprocessor(my_processor)
+
+Example - replace a stored database host with a new one:
+.. code-block:: python
+
+       def my_processor(path):
+          return path.replace('host=10.1.1.115', 'host=10.1.1.116')
+
+       QgsPathResolver.setPathPreprocessor(my_processor)
+
+
+Example - replace stored database credentials with new ones:
+.. code-block:: python
+
+       def my_processor(path):
+          path = path.replace("user='gis_team'", "user='team_awesome'")
+          path = path.replace("password='cats'", "password='g7as!m*'")
+          return path
+
+       QgsPathResolver.setPathPreprocessor(my_processor)
+
+
+
+.. versionadded:: 3.10
+%End
+%MethodCode
+    Py_BEGIN_ALLOW_THREADS
+    Py_XINCREF( a0 );
+    QgsPathResolver::setPathPreprocessor( [a0]( const QString &arg )->QString
+    {
+      QString res;
+      SIP_BLOCK_THREADS
+      PyObject *s = sipCallMethod( NULL, a0, "D", &arg, sipType_QString, NULL );
+      int state;
+      int sipIsError = 0;
+      QString *t1 = reinterpret_cast<QString *>( sipConvertToType( s, sipType_QString, 0, SIP_NOT_NONE, &state, &sipIsError ) );
+      if ( sipIsError == 0 )
+      {
+        res = QString( *t1 );
+      }
+      sipReleaseType( t1, sipType_QString, state );
+      SIP_UNBLOCK_THREADS
+      return res;
+    } );
+
+    Py_END_ALLOW_THREADS
+%End
+
 };
 
 /************************************************************************

src/core/qgspathresolver.cpp

@@ -20,15 +20,17 @@
 #include <QFileInfo>
 #include <QUrl>
 
+std::function< QString( const QString & ) > QgsPathResolver::sCustomResolver = []( const QString &a )->QString { return a; };
 
 QgsPathResolver::QgsPathResolver( const QString &baseFileName )
   : mBaseFileName( baseFileName )
 {
 }
 
 
-QString QgsPathResolver::readPath( const QString &filename ) const
+QString QgsPathResolver::readPath( const QString &f ) const
 {
+  QString filename = sCustomResolver( f );
   if ( filename.isEmpty() )
     return QString();
 
@@ -142,6 +144,11 @@ QString QgsPathResolver::readPath( const QString &filename ) const
   return vsiPrefix + projElems.join( QStringLiteral( "/" ) );
 }
 
+void QgsPathResolver::setPathPreprocessor( const std::function<QString( const QString & )> &processor )
+{
+  sCustomResolver = processor;
+}
+
 QString QgsPathResolver::writePath( const QString &src ) const
 {
   if ( mBaseFileName.isEmpty() || src.isEmpty() )

src/core/qgspathresolver.h

@@ -19,7 +19,7 @@
 #include "qgis_core.h"
 
 #include <QString>
-
+#include <functional>
 
 /**
  * \ingroup core
@@ -43,9 +43,93 @@ class CORE_EXPORT QgsPathResolver
     //! Turn filename read from the project file to an absolute path
     QString readPath( const QString &filename ) const;
 
+#ifndef SIP_RUN
+
+    /**
+     * Sets a path pre-processor function, which allows for manipulation of paths and data sources prior
+     * to resolving them to file references or layer sources.
+     *
+     * The \a processor function must accept a single string argument (representing the original file path
+     * or data source), and return a processed version of this path.
+     *
+     * The path pre-processor function is called before any bad layer handler.
+     *
+     * \note Setting a new \a processor replaces any existing processor.
+     *
+     * \since QGIS 3.10
+     */
+    static void setPathPreprocessor( const std::function< QString( const QString &filename )> &processor );
+#else
+
+    /**
+     * Sets a path pre-processor function, which allows for manipulation of paths and data sources prior
+     * to resolving them to file references or layer sources.
+     *
+     * The \a processor function must accept a single string argument (representing the original file path
+     * or data source), and return a processed version of this path.
+     *
+     * The path pre-processor function is called before any bad layer handler.
+     *
+     * \note Setting a new \a processor replaces any existing processor.
+     *
+     * Example - replace an outdated folder path with a new one:
+     * \code{.py}
+     *   def my_processor(path):
+     *      return path.replace('c:/Users/ClintBarton/Documents/Projects', 'x:/Projects/')
+     *
+     *   QgsPathResolver.setPathPreprocessor(my_processor)
+     * \endcode
+     *
+     * Example - replace a stored database host with a new one:
+     * \code{.py}
+     *   def my_processor(path):
+     *      return path.replace('host=10.1.1.115', 'host=10.1.1.116')
+     *
+     *   QgsPathResolver.setPathPreprocessor(my_processor)
+     * \endcode
+     *
+     * Example - replace stored database credentials with new ones:
+     * \code{.py}
+     *   def my_processor(path):
+     *      path = path.replace("user='gis_team'", "user='team_awesome'")
+     *      path = path.replace("password='cats'", "password='g7as!m*'")
+     *      return path
+     *
+     *   QgsPathResolver.setPathPreprocessor(my_processor)
+     * \endcode
+     *
+     * \since QGIS 3.10
+     */
+    static void setPathPreprocessor( SIP_PYCALLABLE / AllowNone / );
+    % MethodCode
+    Py_BEGIN_ALLOW_THREADS
+    Py_XINCREF( a0 );
+    QgsPathResolver::setPathPreprocessor( [a0]( const QString &arg )->QString
+    {
+      QString res;
+      SIP_BLOCK_THREADS
+      PyObject *s = sipCallMethod( NULL, a0, "D", &arg, sipType_QString, NULL );
+      int state;
+      int sipIsError = 0;
+      QString *t1 = reinterpret_cast<QString *>( sipConvertToType( s, sipType_QString, 0, SIP_NOT_NONE, &state, &sipIsError ) );
+      if ( sipIsError == 0 )
+      {
+        res = QString( *t1 );
+      }
+      sipReleaseType( t1, sipType_QString, state );
+      SIP_UNBLOCK_THREADS
+      return res;
+    } );
+
+    Py_END_ALLOW_THREADS
+    % End
+#endif
+
   private:
     //! path to a file that is the base for relative path resolution
     QString mBaseFileName;
+
+    static std::function< QString( const QString & ) > sCustomResolver;
 };
 
 #endif // QGSPATHRESOLVER_H

tests/src/python/CMakeLists.txt

@@ -159,6 +159,7 @@ ADD_PYTHON_TEST(PyQgsPalLabelingLayout test_qgspallabeling_layout.py)
 ADD_PYTHON_TEST(PyQgsPalLabelingPlacement test_qgspallabeling_placement.py)
 ADD_PYTHON_TEST(PyQgsPanelWidget test_qgspanelwidget.py)
 ADD_PYTHON_TEST(PyQgsPanelWidgetStack test_qgspanelwidgetstack.py)
+ADD_PYTHON_TEST(PyQgsPathResolver test_qgspathresolver.py)
 ADD_PYTHON_TEST(PyQgsPoint test_qgspoint.py)
 ADD_PYTHON_TEST(PyQgsPointClusterRenderer test_qgspointclusterrenderer.py)
 ADD_PYTHON_TEST(PyQgsPointDisplacementRenderer test_qgspointdisplacementrenderer.py)

tests/src/python/test_qgspathresolver.py

@@ -0,0 +1,80 @@
+# -*- coding: utf-8 -*-
+"""QGIS Unit tests for QgsPathResolver.
+
+.. note:: This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+"""
+__author__ = 'Nyall Dawson'
+__date__ = '22/07/2019'
+__copyright__ = 'Copyright 2019, The QGIS Project'
+
+import qgis  # NOQA
+
+import tempfile
+import os
+import gc
+from qgis.core import QgsPathResolver, QgsVectorLayer, QgsProject
+from qgis.testing import start_app, unittest
+from utilities import unitTestDataPath
+
+start_app()
+
+TEST_DATA_DIR = unitTestDataPath()
+
+
+class TestQgsPathResolver(unittest.TestCase):
+
+    def testCustomPreprocessor(self):
+        self.assertEqual(QgsPathResolver().readPath('aaaaa'), 'aaaaa')
+
+        def run_test():
+            def my_processor(path):
+                return path.upper()
+
+            QgsPathResolver.setPathPreprocessor(my_processor)
+            self.assertEqual(QgsPathResolver().readPath('aaaaa'), 'AAAAA')
+
+        run_test()
+        gc.collect()
+        # my_processor should be out of scope and cleaned up, unless things are working
+        # correctly and ownership was transferred
+        self.assertEqual(QgsPathResolver().readPath('aaaaa'), 'AAAAA')
+
+    def testLoadLayerWithPreprocessor(self):
+        """
+        Test that custom path preprocessor is used when loading layers
+        """
+        lines_shp_path = os.path.join(TEST_DATA_DIR, 'moooooo.shp')
+
+        lines_layer = QgsVectorLayer(lines_shp_path, 'Lines', 'ogr')
+        self.assertFalse(lines_layer.isValid())
+        p = QgsProject()
+        p.addMapLayer(lines_layer)
+        # save project to a temporary file
+        temp_path = tempfile.mkdtemp()
+        temp_project_path = os.path.join(temp_path, 'temp.qgs')
+        self.assertTrue(p.write(temp_project_path))
+
+        p2 = QgsProject()
+        self.assertTrue(p2.read(temp_project_path))
+        l = p2.mapLayersByName('Lines')[0]
+        self.assertEqual(l.name(), 'Lines')
+        self.assertFalse(l.isValid())
+
+        # custom processor to fix path
+        def my_processor(path):
+            return path.replace('moooooo', 'lines')
+
+        QgsPathResolver.setPathPreprocessor(my_processor)
+        p3 = QgsProject()
+        self.assertTrue(p3.read(temp_project_path))
+        l = p3.mapLayersByName('Lines')[0]
+        self.assertEqual(l.name(), 'Lines')
+        # layer should have correct path now
+        self.assertTrue(l.isValid())
+
+
+if __name__ == '__main__':
+    unittest.main()