fix use of isdescendant

src/moves_semidirected.jl

@@ -963,11 +963,15 @@ function fliphybrid!(net::HybridNetwork, hybridnode::Node, minor=true::Bool,
             #! 3. in hybrid ladder case: chooses leaf edges as newhybridedge
                 # CAS note: I added additional leaf check to prevent this.
         @debug "$(e !== edgetoflip), $(PhyloNetworks.isdescendant_undirected(p2, newhybridnode, e)), $(!any(n.leaf for n in e.node))"
-        if e !== edgetoflip && PhyloNetworks.isdescendant_undirected(p2, newhybridnode, e) && !any(n.leaf for n in e.node)
-            push!(isdesc, true)
-        else
-            push!(isdesc, false)
+        isp2desc = false
+        if e !== edgetoflip
+            neibr = getOtherNode(e, newhybridnode) # neighbor of new hybrid node via e
+            if !neibr.leaf && (p2 === neibr ||
+                PhyloNetworks.isdescendant_undirected(p2, neibr, e))
+                isp2desc = true
+            end
         end
+        push!(isdesc, isp2desc)
     end
     @debug "isdesc has $(length(isdesc))"
     if sum(isdesc) != 1 # if >1 one edge is an ancestor, flipping would create a cycle

test/test_moves_semidirected.jl

@@ -478,10 +478,10 @@ end # of testset on checknetwork functions for species constraints
 
 end # of constrained NNI moves
 
-@testset "test fliphybrid! inner function" begin
+@testset "test fliphybrid!" begin
 # simple network
 n6h1 = readTopology("((((1:0.2,2:0.2):2.4,((3:0.4,4:0.4):1.1)#H1:1.1):2.0,(#H1:0.0::0.3,5:1.5):3.1):1.0,6:5.6);")
-@test n6h1.hybrid[1].number == 5
+# @test n6h1.hybrid[1].number == 5
 #! currently, rejects an allowable newhybridedge in the following call
 @test !isnothing(PhyloNetworks.fliphybrid!(n6h1, n6h1.hybrid[1])) # flips minor by default
 @test n6h1.hybrid[1].number == -8