[processing] Empty provider nodes should still be shown in toolbox,

unless a filter string is entered

This allows easier discoverability - e.g. without this, the model
and script nodes are hidden until models/scripts have already
been created.

src/gui/processing/qgsprocessingtoolboxmodel.cpp

@@ -722,7 +722,8 @@ bool QgsProcessingToolboxProxyModel::filterAcceptsRow( int sourceRow, const QMod
   }
 
   bool hasChildren = false;
-  // providers and groups are shown only if they have visible children
+  // groups are shown only if they have visible children
+  // but providers are shown if they have visible children, OR the filter string is empty
   int count = sourceModel()->rowCount( sourceIndex );
   for ( int i = 0; i < count; ++i )
   {
@@ -735,7 +736,7 @@ bool QgsProcessingToolboxProxyModel::filterAcceptsRow( int sourceRow, const QMod
 
   if ( QgsProcessingProvider *provider = mModel->providerForIndex( sourceIndex ) )
   {
-    return hasChildren && provider->isActive();
+    return ( hasChildren || mFilterString.trimmed().isEmpty() ) && provider->isActive();
   }
   else
   {

tests/src/gui/testqgsprocessingmodel.cpp

@@ -427,10 +427,15 @@ void TestQgsProcessingModel::testProxyModel()
 
   model.setFilters( QgsProcessingToolboxProxyModel::FilterModeler );
   group1Index = model.index( 0, 0, QModelIndex() );
-  QCOMPARE( model.rowCount(), 1 );
+  QCOMPARE( model.rowCount(), 3 );
   QCOMPARE( model.rowCount( group1Index ), 1 );
   QCOMPARE( model.data( group1Index, Qt::DisplayRole ).toString(), QStringLiteral( "group1" ) );
   QCOMPARE( model.data( model.index( 0, 0, group1Index ), Qt::DisplayRole ).toString(), QStringLiteral( "a2" ) );
+  // no filter string, so empty providers should be shown
+  QCOMPARE( model.data( model.index( 1, 0, QModelIndex() ), Qt::DisplayRole ).toString(), QStringLiteral( "provider1" ) );
+  QCOMPARE( model.rowCount( model.index( 1, 0, QModelIndex() ) ), 0 );
+  QCOMPARE( model.data( model.index( 2, 0, QModelIndex() ), Qt::DisplayRole ).toString(), QStringLiteral( "provider2" ) );
+  QCOMPARE( model.rowCount( model.index( 2, 0, QModelIndex() ) ), 0 );
   model.setFilters( QgsProcessingToolboxProxyModel::FilterToolbox );
   group2Index = model.index( 0, 0, QModelIndex() );
   QCOMPARE( model.rowCount(), 3 );
@@ -586,18 +591,22 @@ void TestQgsProcessingModel::testView()
   QCOMPARE( view.algorithmForIndex( alg1Index )->id(), QStringLiteral( "p2:a1" ) );
 
   view.setFilters( QgsProcessingToolboxProxyModel::FilterModeler );
-  provider2Index = view.model()->index( 0, 0, QModelIndex() );
+  QCOMPARE( view.model()->rowCount(), 2 );
+  QCOMPARE( view.model()->data( view.model()->index( 0, 0, QModelIndex() ), Qt::DisplayRole ).toString(), QStringLiteral( "provider1" ) );
+  QCOMPARE( view.model()->rowCount( view.model()->index( 0, 0, QModelIndex() ) ), 0 );
+  provider2Index = view.model()->index( 1, 0, QModelIndex() );
   QCOMPARE( view.model()->data( provider2Index, Qt::DisplayRole ).toString(), QStringLiteral( "provider2" ) );
-  QCOMPARE( view.model()->rowCount(), 1 );
   QCOMPARE( view.model()->rowCount( provider2Index ), 1 );
   group2Index = view.model()->index( 0, 0, provider2Index );
   QCOMPARE( view.model()->rowCount( group2Index ), 1 );
   QCOMPARE( view.algorithmForIndex( view.model()->index( 0, 0, group2Index ) )->id(), QStringLiteral( "p2:a1" ) );
   view.setFilters( QgsProcessingToolboxProxyModel::FilterToolbox );
+  QCOMPARE( view.model()->rowCount(), 2 );
   provider1Index = view.model()->index( 0, 0, QModelIndex() );
   QCOMPARE( view.model()->data( provider1Index, Qt::DisplayRole ).toString(), QStringLiteral( "provider1" ) );
-  QCOMPARE( view.model()->rowCount(), 1 );
   QCOMPARE( view.model()->rowCount( provider1Index ), 1 );
+  QCOMPARE( view.model()->data( view.model()->index( 1, 0, QModelIndex() ), Qt::DisplayRole ).toString(), QStringLiteral( "provider2" ) );
+  QCOMPARE( view.model()->rowCount( view.model()->index( 1, 0, QModelIndex() ) ), 0 );
   group2Index = view.model()->index( 0, 0, provider1Index );
   QCOMPARE( view.model()->rowCount( group2Index ), 1 );
   QCOMPARE( view.algorithmForIndex( view.model()->index( 0, 0, group2Index ) )->id(), QStringLiteral( "p1:a2" ) );