From 2686f51c57bfd76198da9000b86a7c24d355a686 Mon Sep 17 00:00:00 2001
From: Abdullah Tahiri <abdullah.tahiri.yo@gmail.com>
Date: Mon, 29 May 2017 09:07:20 +0200
Subject: [PATCH] Checking for Document Restoring when extension has a null
 property

==================================================================

The problem:

OriginGroupExtension::OriginGroupExtension () {

    initExtensionType(OriginGroupExtension::getExtensionClassTypeId());

    EXTENSION_ADD_PROPERTY_TYPE ( Origin, (0), 0, App::Prop_Hidden, "Origin linked to the group" );
}

initializes the Origin property to null.

Then Document::Restore => readObjects => addObject => slotNewObject => ViewProviderDocumentObject::updateView => ViewProviderBody::updateData => ViewProviderGeometryObject::updateData =>
ViewProviderDocumentObject::updateData => ViewProvider::updateData => ViewProviderOriginGroupExtension::extensionUpdateData => updateOriginSize() => OriginGroupExtension::getOrigin,

the latter throws an exception because the origin property is null.

Afterwards, the origin property is initialized during Document::Restore => readObjects => ExtensionContainer::Restore() => PropertyContainer::Restore() => App::PropertyLink::Restore()
=> App::PropertyLink::setValue() => Property::hasSetValue, which triggers an onChange: Body::onChanged => BodyBase::onChanged => Feature::onChanged => DocumentObject::onChanged =>
Document::onChangedProperty => Document::slotChangedObject => ViewProviderOriginGroupExtension::slotChangedObjectGui => ViewProviderOriginGroupExtension::updateOriginSize =>
OriginGroupExtension::getOrigin,

now, the latter that is the same that was throwing the exception and generating the error message above, does not throw anymore because Origin has been initialized.

When creating a new object, isNew==true; whereas when loading a file, isNew==false. Therefore, when loading a file setupObject is not executed. SetupObject, effectively initializes
the extension via: Body::setupObject => DocumentObject::setupObject => OriginGroupExtension::onExtendedSetupObject.

DocumentObject * Document::addObject(const char* sType, const char* pObjectName, bool isNew)
{
    [more code here]
    // Call the object-specific initialization
    if (!d->undoing && !d->rollback && isNew) {
        pcObject->setupObject ();
    }
    [more code here]

As DocumentObject code is generic for all objects (workbenches), by design it was chosen to initialize the object only if new. Therefore a object or an extension of a object being restored,
between the addition (addObject) and the restoring of the properties, must by design expect it not to be initialized.

The solution:

Making use of the Restore flag at document level (the one at object level is not sufficient), no exception regarding the null property is reported during document restoring.

Ticket:
https://freecadweb.org/tracker/view.php?id=2530

fixes #2530
---
 src/Gui/ViewProviderOriginGroupExtension.cpp | 4 +++-
 src/Mod/PartDesign/Gui/ViewProviderBody.cpp  | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Gui/ViewProviderOriginGroupExtension.cpp b/src/Gui/ViewProviderOriginGroupExtension.cpp
index 76a98a8994..5026463bc1 100644
--- a/src/Gui/ViewProviderOriginGroupExtension.cpp
+++ b/src/Gui/ViewProviderOriginGroupExtension.cpp
@@ -153,7 +153,9 @@ void ViewProviderOriginGroupExtension::updateOriginSize () {
         assert ( vp->isDerivedFrom ( Gui::ViewProviderOrigin::getClassTypeId () ) );
         vpOrigin = static_cast <Gui::ViewProviderOrigin *> ( vp );
     } catch (const Base::Exception &ex) {
-        Base::Console().Error ("%s\n", ex.what() );
+        // if is restoring it is normal that the origin property is null until after restored, so no need to report this.
+        if(!getExtendedViewProvider()->getDocument()->getDocument()->testStatus(App::Document::Restoring))
+            Base::Console().Error ("%s\n", ex.what() );
         return;
     }
 
diff --git a/src/Mod/PartDesign/Gui/ViewProviderBody.cpp b/src/Mod/PartDesign/Gui/ViewProviderBody.cpp
index 7d61851497..b8654d22e7 100644
--- a/src/Mod/PartDesign/Gui/ViewProviderBody.cpp
+++ b/src/Mod/PartDesign/Gui/ViewProviderBody.cpp
@@ -398,7 +398,8 @@ void ViewProviderBody::updateOriginDatumSize () {
         assert ( vp->isDerivedFrom ( Gui::ViewProviderOrigin::getClassTypeId () ) );
         vpOrigin = static_cast <Gui::ViewProviderOrigin *> ( vp );
     } catch (const Base::Exception &ex) {
-        Base::Console().Error ("%s\n", ex.what() );
+        if(!getExtendedViewProvider()->getDocument()->getDocument()->testStatus(App::Document::Restoring))
+            Base::Console().Error ("%s\n", ex.what() );
         return;
     }