[processing] Allow specifying a project path to load when running

algorithms via qgis_process

Allows execution of algorithms which require a project, e.g. Rasterize

Also show graceful errors/help text when attempting to run an algorithm
which requires a project but one is not specified

src/process/qgsprocess.cpp

@@ -26,6 +26,7 @@
 #include "qgsapplication.h"
 #include "qgsprocessingparametertype.h"
 #include "processing/models/qgsprocessingmodelalgorithm.h"
+#include "qgsproject.h"
 
 #if defined(Q_OS_UNIX) && !defined(Q_OS_ANDROID)
 #include "sigwatch.h"
@@ -219,6 +220,7 @@ int QgsProcessingExec::run( const QStringList &args )
     QString ellipsoid;
     QgsUnitTypes::DistanceUnit distanceUnit = QgsUnitTypes::DistanceUnknownUnit;
     QgsUnitTypes::AreaUnit areaUnit = QgsUnitTypes::AreaUnknownUnit;
+    QString projectPath;
     QVariantMap params;
     for ( int i = 3; i < args.count(); i++ )
     {
@@ -243,6 +245,10 @@ int QgsProcessingExec::run( const QStringList &args )
         {
           areaUnit = QgsUnitTypes::decodeAreaUnit( parts.mid( 1 ).join( '=' ) );
         }
+        else if ( name.compare( QLatin1String( "project_path" ), Qt::CaseInsensitive ) == 0 )
+        {
+          projectPath = parts.mid( 1 ).join( '=' );
+        }
         else
         {
           const QString value = parts.mid( 1 ).join( '=' );
@@ -256,7 +262,7 @@ int QgsProcessingExec::run( const QStringList &args )
       }
     }
 
-    return execute( algId, params, ellipsoid, distanceUnit, areaUnit );
+    return execute( algId, params, ellipsoid, distanceUnit, areaUnit, projectPath );
   }
   else
   {
@@ -276,8 +282,9 @@ void QgsProcessingExec::showUsage( const QString &appName )
       << "\tplugins\tlist available and active plugins\n"
       << "\tlist\tlist all available processing algorithms\n"
       << "\thelp\tshow help for an algorithm. The algorithm id or a path to a model file must be specified.\n"
-      << "\trun\truns an algorithm. The algorithm id or a path to a model file and parameter values must be specified. Parameter values are specified via the --PARAMETER=VALUE syntax. "
-      "If required, the ellipsoid to use for distance and area calculations can be specified via the \"--ELLIPSOID=name\" argument.\n";
+      << "\trun\truns an algorithm. The algorithm id or a path to a model file and parameter values must be specified. Parameter values are specified via the --PARAMETER=VALUE syntax.\n"
+      << "\t\tIf required, the ellipsoid to use for distance and area calculations can be specified via the \"--ELLIPSOID=name\" argument.\n"
+      << "\t\tIf required, an existing QGIS project to use during the algorithm execution can be specified via the \"--PROJECT_PATH=path\" argument.\n";
 
   std::cout << msg.join( QString() ).toLocal8Bit().constData();
 }
@@ -430,7 +437,7 @@ int QgsProcessingExec::showAlgorithmHelp( const QString &id )
   return 0;
 }
 
-int QgsProcessingExec::execute( const QString &id, const QVariantMap &params, const QString &ellipsoid, QgsUnitTypes::DistanceUnit distanceUnit, QgsUnitTypes::AreaUnit areaUnit )
+int QgsProcessingExec::execute( const QString &id, const QVariantMap &params, const QString &ellipsoid, QgsUnitTypes::DistanceUnit distanceUnit, QgsUnitTypes::AreaUnit areaUnit, const QString &projectPath )
 {
   std::unique_ptr< QgsProcessingModelAlgorithm > model;
   const QgsProcessingAlgorithm *alg = nullptr;
@@ -473,6 +480,23 @@ int QgsProcessingExec::execute( const QString &id, const QVariantMap &params, co
       std::cout << "Warning: this algorithm is deprecated and may be removed in a future QGIS version!\n";
       std::cout << "****************\n\n";
     }
+
+    if ( alg->flags() & QgsProcessingAlgorithm::FlagRequiresProject && projectPath.isEmpty() )
+    {
+      std::cerr << QStringLiteral( "The \"%1\" algorithm requires a QGIS project to execute. Specify a path to an existing project with the \"--PROJECT_PATH=xxx\" argument.\n" ).arg( id ).toLocal8Bit().constData();
+      return 1;
+    }
+  }
+
+  std::unique_ptr< QgsProject > project;
+  if ( !projectPath.isEmpty() )
+  {
+    project = qgis::make_unique< QgsProject >();
+    if ( !project->read( projectPath ) )
+    {
+      std::cerr << QStringLiteral( "Could not load the QGIS project \"%1\"\n" ).arg( projectPath ).toLocal8Bit().constData();
+      return 1;
+    }
   }
 
   std::cout << "\n----------------\n";
@@ -496,6 +520,7 @@ int QgsProcessingExec::execute( const QString &id, const QVariantMap &params, co
   context.setEllipsoid( ellipsoid );
   context.setDistanceUnit( distanceUnit );
   context.setAreaUnit( areaUnit );
+  context.setProject( project.get() );
 
   const QgsProcessingParameterDefinitions defs = alg->parameterDefinitions();
   QList< const QgsProcessingParameterDefinition * > missingParams;

src/process/qgsprocess.h

@@ -69,7 +69,12 @@ class QgsProcessingExec
     void listAlgorithms();
     void listPlugins();
     int showAlgorithmHelp( const QString &id );
-    int execute( const QString &algId, const QVariantMap &parameters, const QString &ellipsoid, QgsUnitTypes::DistanceUnit distanceUnit, QgsUnitTypes::AreaUnit areaUnit );
+    int execute( const QString &algId,
+                 const QVariantMap &parameters,
+                 const QString &ellipsoid,
+                 QgsUnitTypes::DistanceUnit distanceUnit,
+                 QgsUnitTypes::AreaUnit areaUnit,
+                 const QString &projectPath = QString() );
 
     std::unique_ptr< QgsPythonUtils > mPythonUtils;
     std::unique_ptr<QgsPythonUtils> loadPythonSupport();