Merge pull request #42296 from domi4484/fixNmRelationMissing

Fix QgsAbstractRelationEditorWidget inconsistency NmRelation / NmRelationId

python/gui/auto_generated/qgsabstractrelationeditorwidget.sip.in

@@ -61,6 +61,13 @@ inserting and deleting entries on the intermediate table as required.
 %Docstring
 Returns the relation
 
+.. versionadded:: 3.18
+%End
+
+    QgsRelation nmRelation() const;
+%Docstring
+Returns the nm relation
+
 .. versionadded:: 3.18
 %End
 

src/gui/editorwidgets/qgsrelationwidgetwrapper.cpp

@@ -268,8 +268,6 @@ void QgsRelationWidgetWrapper::setNmRelationId( const QVariant &nmRelationId )
 {
   if ( mWidget )
   {
-    mWidget->setNmRelationId( nmRelationId );
-
     mNmRelation = QgsProject::instance()->relationManager()->relation( nmRelationId.toString() );
 
     // If this widget is already embedded by the same relation, reduce functionality

src/gui/qgsabstractrelationeditorwidget.cpp

@@ -22,6 +22,7 @@
 #include "qgsfeature.h"
 #include "qgsfeatureselectiondlg.h"
 #include "qgsrelation.h"
+#include "qgsrelationmanager.h"
 #include "qgspolymorphicrelation.h"
 #include "qgsvectorlayertools.h"
 #include "qgsproject.h"
@@ -116,12 +117,16 @@ void QgsAbstractRelationEditorWidget::setFeature( const QgsFeature &feature, boo
 
 void QgsAbstractRelationEditorWidget::setNmRelationId( const QVariant &nmRelationId )
 {
-  mNmRelationId = nmRelationId;
+  QgsRelation nmrelation = QgsProject::instance()->relationManager()->relation( nmRelationId.toString() );
+  beforeSetRelations( mRelation, nmrelation );
+  mNmRelation = nmrelation;
+  afterSetRelations();
+  updateUi();
 }
 
 QVariant QgsAbstractRelationEditorWidget::nmRelationId() const
 {
-  return mNmRelationId;
+  return mNmRelation.id();
 }
 
 QString QgsAbstractRelationEditorWidget::label() const

src/gui/qgsabstractrelationeditorwidget.h

@@ -86,6 +86,12 @@ class GUI_EXPORT QgsAbstractRelationEditorWidget : public QWidget
      */
     QgsRelation relation() const {return mRelation;}
 
+    /**
+     * Returns the nm relation
+     * \since QGIS 3.18
+     */
+    QgsRelation nmRelation() const {return mNmRelation;}
+
     /**
      * Sets the \a feature being edited and updates the UI unless \a update is set to FALSE
      */
@@ -226,7 +232,6 @@ class GUI_EXPORT QgsAbstractRelationEditorWidget : public QWidget
     bool mLayerInSameTransactionGroup = false;
 
     bool mForceSuppressFormPopup = false;
-    QVariant mNmRelationId;
     QString mLabel;
 
     /**