[FEATURE] Add expression context variables for project metadata

- @project_author
- @project_abstract
- @project_creation_date
- @project_identifier
- @project_keywords

Allows retrieval of project metadata through QGIS expressions

Developed for Arpa Piemonte (Dipartimento Tematico Geologia e Dissesto)
within ERIKUS project

Author: nyalldawson

src/core/expression/qgsexpression.cpp

@@ -640,6 +640,11 @@ void QgsExpression::initVariableHelp()
   sVariableHelpTexts.insert( QStringLiteral( "project_home" ), QCoreApplication::translate( "variable_help", "Home path of current project." ) );
   sVariableHelpTexts.insert( QStringLiteral( "project_crs" ), QCoreApplication::translate( "variable_help", "Coordinate reference system of project (e.g., 'EPSG:4326')." ) );
   sVariableHelpTexts.insert( QStringLiteral( "project_crs_definition" ), QCoreApplication::translate( "variable_help", "Coordinate reference system of project (full definition)." ) );
+  sVariableHelpTexts.insert( QStringLiteral( "project_author" ), QCoreApplication::translate( "variable_help", "Project author, taken from project metadata." ) );
+  sVariableHelpTexts.insert( QStringLiteral( "project_abstract" ), QCoreApplication::translate( "variable_help", "Project abstract, taken from project metadata." ) );
+  sVariableHelpTexts.insert( QStringLiteral( "project_creation_date" ), QCoreApplication::translate( "variable_help", "Project creation date, taken from project metadata." ) );
+  sVariableHelpTexts.insert( QStringLiteral( "project_identifier" ), QCoreApplication::translate( "variable_help", "Project identifier, taken from project metadata." ) );
+  sVariableHelpTexts.insert( QStringLiteral( "project_keywords" ), QCoreApplication::translate( "variable_help", "Project keywords, taken from project metadata." ) );
 
   //layer variables
   sVariableHelpTexts.insert( QStringLiteral( "layer_name" ), QCoreApplication::translate( "variable_help", "Name of current layer." ) );

src/core/qgsexpressioncontext.cpp

@@ -788,6 +788,21 @@ QgsExpressionContextScope *QgsExpressionContextUtils::projectScope( const QgsPro
   scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "project_crs" ), projectCrs.authid(), true, true ) );
   scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "project_crs_definition" ), projectCrs.toProj4(), true, true ) );
 
+  // metadata
+  scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "project_author" ), project->metadata().author(), true, true ) );
+  scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "project_abstract" ), project->metadata().abstract(), true, true ) );
+  scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "project_creation_date" ), project->metadata().creationDateTime(), true, true ) );
+  scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "project_identifier" ), project->metadata().identifier(), true, true ) );
+
+  // keywords
+  QVariantMap keywords;
+  QgsAbstractMetadataBase::KeywordMap metadataKeywords = project->metadata().keywords();
+  for ( auto it = metadataKeywords.constBegin(); it != metadataKeywords.constEnd(); ++it )
+  {
+    keywords.insert( it.key(), it.value() );
+  }
+  scope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "project_keywords" ), keywords, true, true ) );
+
   scope->addFunction( QStringLiteral( "project_color" ), new GetNamedProjectColor( project ) );
   return scope;
 }

tests/src/core/testqgsexpressioncontext.cpp

@@ -598,6 +598,18 @@ void TestQgsExpressionContext::globalScope()
 void TestQgsExpressionContext::projectScope()
 {
   QgsProject *project = QgsProject::instance();
+  QgsProjectMetadata md;
+  md.setTitle( QStringLiteral( "project title" ) );
+  md.setAuthor( QStringLiteral( "project author" ) );
+  md.setAbstract( QStringLiteral( "project abstract" ) );
+  md.setCreationDateTime( QDateTime( QDate( 2011, 3, 5 ), QTime( 9, 5, 4 ) ) );
+  md.setIdentifier( QStringLiteral( "project identifier" ) );
+  QgsAbstractMetadataBase::KeywordMap keywords;
+  keywords.insert( QStringLiteral( "voc1" ), QStringList() << "a" << "b" );
+  keywords.insert( QStringLiteral( "voc2" ), QStringList() << "c" << "d" );
+  md.setKeywords( keywords );
+  project->setMetadata( md );
+
   QgsExpressionContextUtils::setProjectVariable( project, QStringLiteral( "test" ), "testval" );
   QgsExpressionContextUtils::setProjectVariable( project, QStringLiteral( "testdouble" ), 5.2 );
 
@@ -606,6 +618,18 @@ void TestQgsExpressionContext::projectScope()
   context << scope;
   QCOMPARE( scope->name(), tr( "Project" ) );
 
+  // metadata variables
+  QCOMPARE( context.variable( "project_title" ).toString(), QStringLiteral( "project title" ) );
+  QCOMPARE( context.variable( "project_author" ).toString(), QStringLiteral( "project author" ) );
+  QCOMPARE( context.variable( "project_abstract" ).toString(), QStringLiteral( "project abstract" ) );
+  QCOMPARE( context.variable( "project_creation_date" ).toDateTime(),  QDateTime( QDate( 2011, 3, 5 ), QTime( 9, 5, 4 ) ) );
+  QCOMPARE( context.variable( "project_identifier" ).toString(), QStringLiteral( "project identifier" ) );
+  QVariantMap keywordsExpected;
+  keywordsExpected.insert( QStringLiteral( "voc1" ), QStringList() << "a" << "b" );
+  keywordsExpected.insert( QStringLiteral( "voc2" ), QStringList() << "c" << "d" );
+  QVariantMap keywordsResult = context.variable( "project_keywords" ).toMap();
+  QCOMPARE( keywordsResult, keywordsExpected );
+
   QCOMPARE( context.variable( "test" ).toString(), QString( "testval" ) );
   QCOMPARE( context.variable( "testdouble" ).toDouble(), 5.2 );