Fixing role dependency chain creation

The dep chain for roles created during the compile step had bugs, in
which the dep chain was overwriten and the original tasks in the role
were not assigned a dep chain. This lead to problems in determining
whether roles had already run when in a "diamond" structure, and in
some cases roles were not correctly getting variables from parents.

Fixes #14046

lib/ansible/playbook/role/__init__.py

@@ -323,7 +323,7 @@ class Role(Base, Become, Conditional, Taggable):
 
         return host.name in self._completed and not self._metadata.allow_duplicates
 
-    def compile(self, play, dep_chain=[]):
+    def compile(self, play, dep_chain=None):
         '''
         Returns the task list for this role, which is created by first
         recursively compiling the tasks for all direct dependencies, and
@@ -337,18 +337,20 @@ class Role(Base, Become, Conditional, Taggable):
         block_list = []
 
         # update the dependency chain here
+        if dep_chain is None:
+            dep_chain = []
         new_dep_chain = dep_chain + [self]
 
         deps = self.get_direct_dependencies()
         for dep in deps:
             dep_blocks = dep.compile(play=play, dep_chain=new_dep_chain)
-            for dep_block in dep_blocks:
-                new_dep_block = dep_block.copy()
-                new_dep_block._dep_chain = new_dep_chain
-                new_dep_block._play = play
-                block_list.append(new_dep_block)
+            block_list.extend(dep_blocks)
 
-        block_list.extend(self._task_blocks)
+        for task_block in self._task_blocks:
+            new_task_block = task_block.copy()
+            new_task_block._dep_chain = new_dep_chain
+            new_task_block._play = play
+            block_list.append(new_task_block)
 
         return block_list