Added `bool supportsEditing` property to QgsVectorLayer

python/core/auto_generated/qgsvectorlayer.sip.in

@@ -1789,6 +1789,15 @@ If you need only the count of committed features call this method on this layer'
 Makes layer read-only (editing disabled) or not
 
 :return: ``False`` if the layer is in editing yet
+%End
+
+    bool supportsEditing();
+%Docstring
+Returns whether the layer supports editing or not
+
+:return: ``False`` if the layer is read only or the data provider has no editing capabilities
+
+.. versionadded:: 3.18
 %End
 
     bool changeGeometry( QgsFeatureId fid, QgsGeometry &geometry, bool skipDefaultValue = false );
@@ -2921,6 +2930,13 @@ Emitted when the read only state of this layer is changed.
 Only applies to manually set readonly state, not to the edit mode.
 
 .. versionadded:: 3.0
+%End
+
+    void supportsEditingChanged();
+%Docstring
+Emitted when the read only state or the data provider of this layer is changed.
+
+.. versionadded:: 3.18
 %End
 
     void symbolFeatureCountMapChanged();

src/app/qgisapp.cpp

         bool canChangeAttributes = dprovider->capabilities() & QgsVectorDataProvider::ChangeAttributeValues;
         bool canDeleteFeatures = dprovider->capabilities() & QgsVectorDataProvider::DeleteFeatures;
         bool canAddFeatures = dprovider->capabilities() & QgsVectorDataProvider::AddFeatures;
-        bool canSupportEditing = dprovider->capabilities() & QgsVectorDataProvider::EditingCapabilities;
         bool canChangeGeometry = isSpatial && dprovider->capabilities() & QgsVectorDataProvider::ChangeGeometries;
+        bool canSupportEditing = vlayer->supportsEditing();
 
         mActionLayerSubsetString->setEnabled( !isEditable && dprovider->supportsSubsetString() );
 
-        mActionToggleEditing->setEnabled( canSupportEditing && !vlayer->readOnly() );
+        mActionToggleEditing->setEnabled( canSupportEditing );
         mActionToggleEditing->setChecked( canSupportEditing && isEditable );
         mActionSaveLayerEdits->setEnabled( canSupportEditing && isEditable && vlayer->isModified() );
         mUndoDock->widget()->setEnabled( canSupportEditing && isEditable );

src/core/qgsvectorlayer.cpp

@@ -201,6 +201,8 @@ QgsVectorLayer::QgsVectorLayer( const QString &vectorLayerPath,
   connect( QgsProject::instance()->relationManager(), &QgsRelationManager::relationsLoaded, this, &QgsVectorLayer::onRelationsLoaded );
 
   connect( this, &QgsVectorLayer::subsetStringChanged, this, &QgsMapLayer::configChanged );
+  connect( this, &QgsVectorLayer::dataSourceChanged, this, &QgsVectorLayer::supportsEditingChanged );
+  connect( this, &QgsVectorLayer::readOnlyChanged, this, &QgsVectorLayer::supportsEditingChanged );
 
   // Default simplify drawing settings
   QgsSettings settings;
@@ -3667,6 +3669,14 @@ bool QgsVectorLayer::setReadOnly( bool readonly )
   return true;
 }
 
+bool QgsVectorLayer::supportsEditing()
+{
+  if ( ! mDataProvider )
+    return false;
+
+  return mDataProvider->capabilities() & QgsVectorDataProvider::EditingCapabilities && ! mReadOnly;
+}
+
 bool QgsVectorLayer::isModified() const
 {
   emit beforeModifiedCheck();

src/core/qgsvectorlayer.h

@@ -392,6 +392,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     Q_PROPERTY( QString mapTipTemplate READ mapTipTemplate WRITE setMapTipTemplate NOTIFY mapTipTemplateChanged )
     Q_PROPERTY( QgsEditFormConfig editFormConfig READ editFormConfig WRITE setEditFormConfig NOTIFY editFormConfigChanged )
     Q_PROPERTY( bool readOnly READ isReadOnly WRITE setReadOnly NOTIFY readOnlyChanged )
+    Q_PROPERTY( bool supportsEditing READ supportsEditing NOTIFY supportsEditingChanged )
 
   public:
 
@@ -1691,6 +1692,13 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      */
     bool setReadOnly( bool readonly = true );
 
+    /**
+     * Returns whether the layer supports editing or not
+     * \return FALSE if the layer is read only or the data provider has no editing capabilities
+     * \since QGIS 3.18
+     */
+    bool supportsEditing();
+
     /**
      * Changes a feature's \a geometry within the layer's edit buffer
      * (but does not immediately commit the changes). The \a fid argument
@@ -2718,6 +2726,13 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      */
     void readOnlyChanged();
 
+    /**
+     * Emitted when the read only state or the data provider of this layer is changed.
+     *
+     * \since QGIS 3.18
+     */
+    void supportsEditingChanged();
+
     /**
      * Emitted when the feature count for symbols on this layer has been recalculated.
      *