Keep track of role dependencies across plays

Also fixes a bug in which tags specified on top-level roles were
not being passed down to dependent roles.

Fixes #4656

CHANGELOG.md

@@ -6,6 +6,7 @@ Ansible Changes By Release
 Major features/changes:
 
 * The deprecated legacy variable templating system has been finally removed.  Use {{ foo }} always not $foo or ${foo}.
+* Role dependencies are now tracked across multiple plays, making common roles easier to include in dependencies without any special variable tricks.
 
 New Modules:
 

lib/ansible/playbook/__init__.py

@@ -240,13 +240,20 @@ class PlayBook(object):
         plays = []
         matched_tags_all = set()
         unmatched_tags_all = set()
+        included_roles = []
 
         # loop through all patterns and run them
         self.callbacks.on_start()
         for (play_ds, play_basedir) in zip(self.playbook, self.play_basedirs):
-            play = Play(self, play_ds, play_basedir, vault_password=self.vault_password)
+            play = Play(self, play_ds, play_basedir, included_roles=included_roles, vault_password=self.vault_password)
             assert play is not None
 
+            # add any new roles brought in by this play to the 
+            # global list of roles we're tracking
+            for role in play.included_roles:
+                if role not in included_roles:
+                    included_roles.append(role)
+
             matched_tags, unmatched_tags = play.compare_tags(self.only_tags)
             matched_tags_all = matched_tags_all | matched_tags
             unmatched_tags_all = unmatched_tags_all | unmatched_tags

lib/ansible/playbook/play.py

@@ -49,7 +49,7 @@ class Play(object):
 
     # *************************************************
 
-    def __init__(self, playbook, ds, basedir, vault_password=None):
+    def __init__(self, playbook, ds, basedir, included_roles=[], vault_password=None):
         ''' constructor loads from a play datastructure '''
 
         for x in ds.keys():
@@ -81,7 +81,7 @@ class Play(object):
         self._update_vars_files_for_host(None)
 
         # now we load the roles into the datastructure
-        self.included_roles = []
+        self.included_roles = included_roles
         ds = self._load_roles(self.roles, ds)
         
         # and finally re-process the vars files as they may have
@@ -227,6 +227,20 @@ class Play(object):
                             if meta_data:
                                 allow_dupes = utils.boolean(meta_data.get('allow_duplicates',''))
 
+                        # if any tags were specified as role/dep variables, merge
+                        # them into the passed_vars so they're passed on to any 
+                        # further dependencies too, and so we only have one place
+                        # (passed_vars) to look for tags going forward
+                        def __merge_tags(var_obj):
+                            old_tags = passed_vars.get('tags', [])
+                            new_tags = var_obj.get('tags', [])
+                            if isinstance(new_tags, basestring):
+                                new_tags = [new_tags, ]
+                            return list(set(old_tags + new_tags))
+
+                        passed_vars['tags'] = __merge_tags(role_vars)
+                        passed_vars['tags'] = __merge_tags(dep_vars)
+
                         # if tags are set from this role, merge them
                         # into the tags list for the dependent role
                         if "tags" in passed_vars: