mockingbirdnest · Feb 16, 2019 · Feb 16, 2019 · Feb 16, 2019
Showing with 21 additions and 3 deletions.

+1 −2 physics/discrete_trajectory_body.hpp

+6 −0 physics/discrete_trajectory_test.cpp

+4 −1 physics/forkable_body.hpp

+10 −0 physics/forkable_test.cpp
diff --git a/physics/discrete_trajectory_body.hpp b/physics/discrete_trajectory_body.hpp
@@ -239,10 +239,9 @@ void DiscreteTrajectory<Frame>::ForgetBefore(Instant const& time) {
   // Get an iterator denoting the first entry with time >= |time|.  Remove all
   // the entries that precede it.  This preserves any entry with time == |time|.
   auto const first_kept_in_timeline = timeline_.lower_bound(time);
-  Instant const& first_kept_time = first_kept_in_timeline->first;
   if (downsampling_.has_value() &&
       (first_kept_in_timeline == timeline_.end() ||
-       downsampling_->first_dense_time() < first_kept_time)) {
+       downsampling_->first_dense_time() < first_kept_in_timeline->first)) {
     // The start of the dense timeline will be invalidated.
     downsampling_->SetStartOfDenseTimeline(first_kept_in_timeline, timeline_);
   }

diff --git a/physics/discrete_trajectory_test.cpp b/physics/discrete_trajectory_test.cpp
@@ -666,6 +666,12 @@ TEST_F(DiscreteTrajectoryTest, ForgetBeforeSuccess) {
   EXPECT_THAT(times, ElementsAre(t2_, t3_));
 }
 
+TEST_F(DiscreteTrajectoryTest, ForgetBeforeEmpty) {
+  massive_trajectory_->Append(t1_, d1_);
+  massive_trajectory_->ForgetBefore(t4_);
+  EXPECT_TRUE(massive_trajectory_->Empty());
+}
+
 TEST_F(DiscreteTrajectoryDeathTest, TrajectorySerializationError) {
   EXPECT_DEATH({
     massive_trajectory_->Append(t1_, d1_);

diff --git a/physics/forkable_body.hpp b/physics/forkable_body.hpp
@@ -365,7 +365,10 @@ void Forkable<Tr4jectory, It3rator>::AttachForkToCopiedBegin(
   // Set the pointer into this object.  Note that |fork| is no longer usable.
   child_it->second->parent_ = that();
   child_it->second->position_in_parent_children_ = child_it;
-  child_it->second->position_in_parent_timeline_ = --timeline_end();
+  child_it->second->position_in_parent_timeline_ = timeline_end();
+  if (!timeline_empty()) {
+    --*child_it->second->position_in_parent_timeline_;
+  }
 }
 
 template<typename Tr4jectory, typename It3rator>

diff --git a/physics/forkable_test.cpp b/physics/forkable_test.cpp
@@ -359,6 +359,16 @@ TEST_F(ForkableTest, AttachForkWithCopiedBeginSuccess) {
   EXPECT_THAT(times, ElementsAre(t1_, t2_, t3_, t4_));
 }
 
+TEST_F(ForkableTest, AttachForkWithCopiedBeginEmpty) {
+  trajectory_.push_back(t1_);
+  not_null<FakeTrajectory*> const fork1 =
+      trajectory_.NewFork(trajectory_.timeline_find(t1_));
+  not_null<std::unique_ptr<FakeTrajectory>> fork2 =
+      make_not_null_unique<FakeTrajectory>();
+  fork2->push_back(t3_);
+  fork1->AttachForkToCopiedBegin(std::move(fork2));
+}
+
 TEST_F(ForkableDeathTest, DetachForkWithCopiedBeginError) {
   EXPECT_DEATH({
     trajectory_.push_back(t1_);