LiveScene: Avoid throwing for hash API.

We don't want to throw for hashing API that can be expected by external
client code and we simply ignore hashing for the feature we dont support yet ( attributes, sets... )

Author: lucienfostier

src/IECoreNuke/LiveScene.cpp

@@ -252,17 +252,16 @@ void LiveScene::writeTransform( const Data *transform, double time )
 
 bool LiveScene::hasAttribute( const Name &name ) const
 {
-	throw Exception( "IECoreNuke::LiveScene does not support hasAttribute()." );
+	return false;
 }
 
 void LiveScene::attributeNames( NameList &attrs ) const
 {
-	throw Exception( "IECoreNuke::LiveScene does not support attributeNames()." );
 }
 
 ConstObjectPtr LiveScene::readAttribute( const Name &name, double time ) const
 {
-	throw Exception( "IECoreNuke::LiveScene does not support readAttribute()." );
+	return IECore::NullObject::defaultNullObject();
 }
 
 void LiveScene::writeAttribute( const Name &name, const Object *attribute, double time )
@@ -272,12 +271,11 @@ void LiveScene::writeAttribute( const Name &name, const Object *attribute, doubl
 
 bool LiveScene::hasTag( const Name &name, int filter ) const
 {
-	throw Exception( "IECoreNuke::LiveScene does not support hasTag()." );
+	return false;
 }
 
 void LiveScene::readTags( NameList &tags, int filter ) const
 {
-	throw Exception( "IECoreNuke::LiveScene does not support readTags()." );
 }
 
 void LiveScene::writeTags( const NameList &tags )
@@ -287,12 +285,12 @@ void LiveScene::writeTags( const NameList &tags )
 
 SceneInterface::NameList LiveScene::setNames( bool includeDescendantSets ) const
 {
-	throw Exception( "IECoreNuke::LiveScene::setNames not supported" );
+	return SceneInterface::NameList();
 }
 
 IECore::PathMatcher LiveScene::readSet( const Name &name, bool includeDescendantSets, const IECore::Canceller *canceller ) const
 {
-	throw Exception( "IECoreNuke::LiveScene::readSet not supported" );
+	return IECore::PathMatcher();
 }
 
 void LiveScene::writeSet( const Name &name, const IECore::PathMatcher &set )
@@ -302,7 +300,6 @@ void LiveScene::writeSet( const Name &name, const IECore::PathMatcher &set )
 
 void LiveScene::hashSet( const Name& setName, IECore::MurmurHash &h ) const
 {
-	throw Exception( "IECoreNuke::LiveScene::hashSet not supported" );
 }
 
 bool LiveScene::hasObject() const
@@ -487,5 +484,7 @@ SceneInterfacePtr LiveScene::scene( const Path &path, MissingBehaviour missingBe
 
 void LiveScene::hash( HashType hashType, double time, MurmurHash &h ) const
 {
-	throw Exception( "Hashes currently not supported in IECoreNuke::LiveScene objects." );
+	Path p;
+	path( p );
+	h.append( &( p[0] ), p.size() );
 }