Fix backchaining

Search anchor point only in Selector, Sequence nodes to avoid Decorators
with children

When latching multiple chains always latch next chain to first one to
avoid problems that may arise when last chain were simplified to one
action and don't have a sequence anymore

Author: Peter-Sh

src/redis_release/bht/backchain.py

@@ -17,8 +17,14 @@
 def find_chain_anchor_point(
     root: Behaviour,
 ) -> Sequence:
+    """Find the anchor point (Sequence) to which we can latch the next chain.
+
+    We assume that the anchor point is the leftmost non empty Sequence in the tree.
+    """
     for child in root.children:
-        if len(child.children) > 1:
+        if (isinstance(child, Sequence) or isinstance(child, Selector)) and len(
+            child.children
+        ) > 0:
             return find_chain_anchor_point(child)
     if isinstance(root, Sequence):
         return root
@@ -31,7 +37,6 @@ def latch_chains(*chains: Union[Selector, Sequence]) -> None:
     first = chains[0]
     for chain in chains[1:]:
         latch_chain_to_chain(first, chain)
-        first = chain
 
 
 def latch_chain_to_chain(
@@ -55,7 +60,7 @@ def latch_chain_to_chain(
     next_postcondition: Optional[Behaviour] = None
     anchor_precondition: Optional[Behaviour] = None
 
-    logger.debug(f"Latching {next.name} to {anchor_point.name}")
+    logger.debug(f'Latching "{next.name}" to "{anchor_point.name}"')
 
     # Trying to guess from the structure which node may be a postcondition
     # Later we compare it with the anchor point precondition and when they match