correction merg_n_ancestors

Author: GertjanBisschop

lib/msprime.c

@@ -3280,14 +3280,16 @@ msp_merge_n_ancestors(msp_t *self, avl_tree_t *Q, population_id_t population_id,
 
     if (num_common_ancestors == 1) {
         merged_head = msp_priority_queue_pop(self, Q);
-        if (self->store_unary && self->model.type == MSP_MODEL_DTWF) {
-            ret = msp_store_node(
-                /*FIXME: not a CA_EVENT but PASS_THROUGH_EVENT*/
-                self, MSP_NODE_IS_CA_EVENT, self->time, population_id, TSK_NULL);
-            if (ret < 0) {
-                goto out;
+        if (self->store_unary) {
+            if (self->model.type == MSP_MODEL_DTWF) {
+                ret = msp_store_node(
+                    /*FIXME: not a CA_EVENT but PASS_THROUGH_EVENT*/
+                    self, MSP_NODE_IS_CA_EVENT, self->time, population_id, TSK_NULL);
+                if (ret < 0) {
+                    goto out;
+                }
             }
-            ret = msp_store_arg_edges(self, merged_head, TSK_NULL);
+            ret = msp_store_arg_edges(self, merged_head, new_node_id);
             if (ret < 0) {
                 goto out;
             }

tests/test_pedigree.py

@@ -1548,6 +1548,25 @@ def test_pedigree_unary(self):
         )
         self.verify_pedigree_unary(ts)
 
+    def test_pedigree_unary_simple(self):
+        sequence_length = 100
+        pb = msprime.PedigreeBuilder()
+        mmid = pb.add_individual(time=2)
+        mdid = pb.add_individual(time=2)
+        dmid = pb.add_individual(time=2)
+        ddid = pb.add_individual(time=2)
+        mid = pb.add_individual(time=1, parents=[mmid, mdid])
+        did = pb.add_individual(time=1, parents=[dmid, ddid])
+        pb.add_individual(time=0, parents=[mid, did], is_sample=True)
+        pedigree = pb.finalise(sequence_length)
+        ts = msprime.sim_ancestry(
+            recombination_rate=0.1,
+            model="fixed_pedigree",
+            record_unary=True,
+            initial_state=pedigree,
+        )
+        self.verify_pedigree_unary(ts)
+
     def verify_pedigree_unary(self, ts):
         direct_ancestors = [set() for _ in range(ts.num_nodes)]