Add a parameter cloneRelations for clone to be able not to clone …

…the collections (#609)

* Fix the equal comparison for relations of cloned objects

* Fix pre-commit

* Revert previous commits

This reverts commit e8b962a.

* Add a parameter to clone with empty relations

* Add tests adding to the relations of cloned objects

* Change from emptyRelations to cloneRelations

* Remove std::cout in the test case

* Add short documentation for cloning

---------

Co-authored-by: jmcarcell <[email protected]>
Co-authored-by: tmadlener <[email protected]>

doc/examples.md

@@ -86,6 +86,16 @@ and via direct object access:
     }
 ```
 
+### Cloneing objects
+
+In order to clone objects it is necessary to use the `clone` method which
+returns a `Mutable` object again. `clone` takes a parameter `cloneRelations`
+which is defaulted to `true`. By default the relation information of the
+original object is simply copied over, changing this to `false` only copies the
+data but none of the relations.
+
+![](figures/object_clone.svg)
+
 ### Support for Notebook-Pattern
 
 The `notebook pattern` uses the assumption that it is better to create a small

python/templates/MutableObject.cc.jinja2

@@ -16,7 +16,7 @@
 
 {{ utils.namespace_open(class.namespace) }}
 
-{{ macros.constructors_destructors(class.bare_type, Members, prefix='Mutable') }}
+{{ macros.constructors_destructors(class.bare_type, Members, multi_relations=OneToManyRelations + VectorMembers, prefix='Mutable') }}
 
 {{ macros.member_getters(class, Members, use_get_syntax, prefix='Mutable') }}
 {{ macros.single_relation_getters(class, OneToOneRelations, use_get_syntax, prefix='Mutable') }}

python/templates/macros/declarations.jinja2

@@ -74,7 +74,8 @@
   {{  full_type }}& operator=({{ full_type }} other);
 
   /// create a mutable deep-copy of the object with identical relations
-  Mutable{{ type }} clone() const;
+  /// if cloneRelations=false, the relations are not cloned and will be empty
+  Mutable{{ type }} clone(bool cloneRelations=true) const;
 
   /// destructor
   ~{{  full_type }}() = default;

python/templates/macros/implementations.jinja2

@@ -18,22 +18,41 @@
   return *this;
 }
 
-Mutable{{ type }} {{ full_type }}::clone() const {
+Mutable{{ type }} {{ full_type }}::clone(bool cloneRelations) const {
 {% if prefix %}
+  if (!cloneRelations) {
+    auto tmp = new {{ type }}Obj(podio::ObjectID{}, m_obj->data);
+{% for relation in multi_relations %}
+    tmp->m_{{ relation.name }} = new std::vector<{{ relation.full_type }}>();
+    tmp->data.{{ relation.name }}_begin = 0;
+    tmp->data.{{ relation.name }}_end = 0;
+{% endfor %}
+    return Mutable{{ type }}(podio::utils::MaybeSharedPtr(tmp, podio::utils::MarkOwned));
+  }
   return Mutable{{ type }}(podio::utils::MaybeSharedPtr(new {{ type }}Obj(*m_obj), podio::utils::MarkOwned));
 {% else %}
   auto tmp = new {{ type }}Obj(podio::ObjectID{}, m_obj->data);
 {% for relation in multi_relations %}
   tmp->m_{{ relation.name }} = new std::vector<{{ relation.full_type }}>();
-  // If the current object has been read from a file, then the object may only have a slice of the relation vector
-  // so this slice has to be copied in case we want to modify it
-  tmp->m_{{ relation.name }}->reserve(m_obj->m_{{ relation.name }}->size());
-  for (size_t i = m_obj->data.{{ relation.name }}_begin; i < m_obj->data.{{ relation.name }}_end; i++) {
-    tmp->m_{{ relation.name }}->emplace_back((*m_obj->m_{{ relation.name }})[i]);
+{% endfor %}
+  if (cloneRelations) {
+{% for relation in multi_relations %}
+    // If the current object has been read from a file, then the object may only have a slice of the relation vector
+    // so this slice has to be copied in case we want to modify it
+    tmp->m_{{ relation.name }}->reserve(m_obj->m_{{ relation.name }}->size());
+    for (size_t i = m_obj->data.{{ relation.name }}_begin; i < m_obj->data.{{ relation.name }}_end; i++) {
+      tmp->m_{{ relation.name }}->emplace_back((*m_obj->m_{{ relation.name }})[i]);
+    }
+    tmp->data.{{ relation.name }}_begin = 0;
+    tmp->data.{{ relation.name }}_end = tmp->m_{{ relation.name }}->size();
+{% endfor %}
   }
-  tmp->data.{{ relation.name }}_begin = 0;
-  tmp->data.{{ relation.name }}_end = tmp->m_{{ relation.name }}->size();
+  else {
+{% for relation in multi_relations %}
+    tmp->data.{{ relation.name }}_begin = 0;
+    tmp->data.{{ relation.name }}_end = 0;
 {% endfor %}
+  }
   return Mutable{{ type }}(podio::utils::MaybeSharedPtr(tmp, podio::utils::MarkOwned));
 {% endif %}
 }

tests/unittests/unittest.cpp

@@ -1385,3 +1385,31 @@ TEST_CASE("Relations after cloning with SIO", "[relations][basics]") {
 }
 
 #endif
+
+TEST_CASE("Clone empty relations", "[relations][basics]") {
+  auto coll = ExampleClusterCollection();
+  coll.create();
+  coll.create();
+  coll[0].addHits(ExampleHit());
+  coll[0].addHits(ExampleHit());
+  auto newColl = ExampleClusterCollection();
+  newColl.push_back(coll.at(0).clone(false));
+  newColl.push_back(coll.at(1).clone(false));
+  REQUIRE(newColl[0].Hits().empty());
+  REQUIRE(newColl[1].Hits().empty());
+  newColl[0].addHits(ExampleHit());
+  REQUIRE(newColl[0].Hits().size() == 1);
+  newColl[0].addHits(ExampleHit());
+  REQUIRE(newColl[0].Hits().size() == 2);
+
+  auto immCluster = ExampleCluster(coll.at(0));
+  auto immCluster2 = ExampleCluster(coll.at(1));
+  auto clonedImmCluster = immCluster.clone(false);
+  auto clonedImmCluster2 = immCluster2.clone(false);
+  REQUIRE(clonedImmCluster.Hits().empty());
+  REQUIRE(clonedImmCluster2.Hits().empty());
+  clonedImmCluster.addHits(ExampleHit());
+  REQUIRE(clonedImmCluster.Hits().size() == 1);
+  clonedImmCluster.addHits(ExampleHit());
+  REQUIRE(clonedImmCluster.Hits().size() == 2);
+}