From da0f8102829f343d066ad3940bb603e106ca95a2 Mon Sep 17 00:00:00 2001
From: Ian Rees <ian.rees@gmail.com>
Date: Sun, 19 Feb 2017 13:22:55 +1300
Subject: [PATCH] Avoid empty meshes. Improve object type detection.

---
 src/Mod/Mesh/App/AppMeshPy.cpp |  8 ++++++--
 src/Mod/Mesh/App/Exporter.cpp  | 18 ++++++++----------
 src/Mod/Mesh/App/Exporter.h    |  3 +--
 3 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/src/Mod/Mesh/App/AppMeshPy.cpp b/src/Mod/Mesh/App/AppMeshPy.cpp
index 811446389..76d044ab5 100644
--- a/src/Mod/Mesh/App/AppMeshPy.cpp
+++ b/src/Mod/Mesh/App/AppMeshPy.cpp
@@ -315,7 +315,12 @@ private:
         std::string outputFileName(fileNamePy);
         PyMem_Free(fileNamePy);
 
-        MeshObject global_mesh;
+        // Construct list of objects to export before making the Exporter, so
+        // we don't get empty exports if the list can't be constructed.
+        Py::Sequence list(objects);
+        if (list.length() == 0) {
+            return Py::None();
+        }
 
         auto exportFormat( MeshOutput::GetFormat(outputFileName.c_str()) );
 
@@ -338,7 +343,6 @@ private:
             throw Py::Exception(Base::BaseExceptionFreeCADError, exStr.c_str());
         }
 
-        Py::Sequence list(objects);
         for (auto it : list) {
             PyObject *item = it.ptr();
             if (PyObject_TypeCheck(item, &(App::DocumentObjectPy::Type))) {
diff --git a/src/Mod/Mesh/App/Exporter.cpp b/src/Mod/Mesh/App/Exporter.cpp
index 532aa5b49..bea12f40e 100644
--- a/src/Mod/Mesh/App/Exporter.cpp
+++ b/src/Mod/Mesh/App/Exporter.cpp
@@ -47,9 +47,8 @@ using namespace MeshCore;
 
 Exporter::Exporter() :
     meshFeatId( Base::Type::fromName("Mesh::Feature") ),
-    partFeatId( Base::Type::fromName("Part::Feature") ),
-    appPartId( Base::Type::fromName("App::Part") ),
-    appDOGId( Base::Type::fromName("App::DocumentObjectGroup") )
+    appPartId( Base::Type::fromName("Part::Feature") ),
+    groupExtensionId( App::GroupExtension::getExtensionClassTypeId() )
 { }
 
 //static
@@ -68,13 +67,13 @@ bool Exporter::addAppGroup(App::DocumentObject *obj, float tol)
 {
     auto ret(true);
 
-    for (auto it : static_cast<App::Part *>(obj)->getOutList()) {
+    auto groupEx( obj->getExtensionByType<App::GroupExtension>() );
+    for (auto it : groupEx->Group.getValues()) {
         if (it->getTypeId().isDerivedFrom(meshFeatId)) {
             ret &= addMeshFeat(it);
-        } else if (it->getTypeId().isDerivedFrom(partFeatId)) {
+        } else if (it->getTypeId().isDerivedFrom(appPartId)) {
             ret &= addPartFeat(it, tol);
-        } else if ( it->getTypeId().isDerivedFrom(appPartId) ||
-                    it->getTypeId().isDerivedFrom(appDOGId) ) {
+        } else if (it->hasExtension(groupExtensionId)) {
             // Recurse
             ret &= addAppGroup(it, tol);
         }
@@ -87,10 +86,9 @@ bool Exporter::addObject(App::DocumentObject *obj, float tol)
 {
     if (obj->getTypeId().isDerivedFrom(meshFeatId)) {
         return addMeshFeat( obj );
-    } else if (obj->getTypeId().isDerivedFrom(partFeatId)) {
+    } else if (obj->getTypeId().isDerivedFrom(appPartId)) {
         return addPartFeat( obj, tol );
-    } else if ( obj->getTypeId().isDerivedFrom(appPartId) ||
-                obj->getTypeId().isDerivedFrom(appDOGId) ) {
+    } else if (obj->hasExtension(groupExtensionId)) {
         return addAppGroup( obj, tol );
     } else {
         Base::Console().Message(
diff --git a/src/Mod/Mesh/App/Exporter.h b/src/Mod/Mesh/App/Exporter.h
index d2f195bde..72dba3387 100644
--- a/src/Mod/Mesh/App/Exporter.h
+++ b/src/Mod/Mesh/App/Exporter.h
@@ -71,9 +71,8 @@ class Exporter
         static std::string xmlEscape(const std::string &input);
 
         const Base::Type meshFeatId;
-        const Base::Type partFeatId;
         const Base::Type appPartId;
-        const Base::Type appDOGId;
+        const Base::Type groupExtensionId;
 };
 
 /// Creates a single mesh, in a file, from one or more objects