Squashed commit of the following:

commit 4430ce3eefcdff0b0ceffea0ef66ea8e876a807d
Merge: 631783b 649963c
Author: Michael DeHaan <michael.dehaan@gmail.com>
Date:   Thu Jul 12 01:28:43 2012 -0400

    Merge branch 'host-groups' of https://github.com/dagwieers/ansible into daggroups

commit 649963ca2c
Author: Dag Wieërs <dag@wieers.com>
Date:   Thu Jul 12 23:01:00 2012 +0200

    Added comments in the example yaml file as requested

commit 7f9718f185
Author: Dag Wieërs <dag@wieers.com>
Date:   Thu Jul 12 22:49:38 2012 +0200

    Add the default nose color too, to test specific overrides

commit eb63b9e899
Author: Dag Wieërs <dag@wieers.com>
Date:   Thu Jul 12 22:44:35 2012 +0200

    Introduce comics and cartoons to test yaml groups defined on a per-node basis

commit aa13d23307
Author: Dag Wieërs <dag@wieers.com>
Date:   Thu Jul 12 19:33:15 2012 +0200

    A small fix to revert to old state

commit 264ebaa77c
Author: Dag Wieërs <dag@wieers.com>
Date:   Thu Jul 12 19:31:51 2012 +0200

    Combine both yaml unit tests into one example file

commit 7db49a8048
Author: Dag Wieërs <dag@wieers.com>
Date:   Thu Jul 12 16:46:53 2012 +0200

    Might as well fix this too

commit f36c6c8c5b
Author: Dag Wieërs <dag@wieers.com>
Date:   Thu Jul 12 16:42:00 2012 +0200

    Added unit tests for host-groups patch

    For the unit test I chose to keep the original yaml file in place as a reference.

    This patch also includes a fix.

commit a96f681352
Author: Dag Wieërs <dag@wieers.com>
Date:   Thu Jul 12 12:30:43 2012 +0200

    Allow groups to be defined on a per-host basis

    This makes it possible to define on a per-host basis what groups a host is in.
    When managing a large set of systems it makes it easier to ensure each of the
    systems is defined in a set of groups (e.g. production/qa/development,
    linux/solaris/aix) rather than having to add systems to multiple disconnected
    groups.

    ----
      - host: system01

      - host: system02

      - host: system03

      - group: linux
        hosts:
        - system01
        - system02

      - group: solaris
        hosts:
        - system03

      - group: production
        hosts:
        - system01
        - system03

      - group: qa
        - system02

      - group: dbserver
        hosts:
        - system01

      - group: ntpserver
        hosts:
        - system02

      - group: webserver
        - system03
    ----

    Can be redefined as:

    ----
      - host: system01
        groups: [ linux, production, dbserver ]

      - host: system02
        groups: [ linux, qa, ntpserver ]

      - host: system03
        groups: [ solaris, production, webserver ]
    ----

lib/ansible/inventory/yaml.py

@@ -106,6 +106,7 @@ class InventoryParserYaml(object):
 
             elif type(item) == dict and 'host' in item:
                 host = self._make_host(item['host'])
+
                 vars = item.get('vars', {})
                 if type(vars)==list:
                     varlist, vars = vars, {}
@@ -113,5 +114,23 @@ class InventoryParserYaml(object):
                         vars.update(subitem)
                 for (k,v) in vars.items():
                    host.set_variable(k,v)
+
+                groups = item.get('groups', {})
+                if type(groups) in [ str, unicode ]:
+                    groups = [ groups ]
+                if type(groups)==list:
+                    for subitem in groups:
+                        if subitem in self.groups:
+                            group = self.groups[subitem]
+                        else:
+                            group = Group(subitem)
+                            self.groups[group.name] = group
+                            all.add_child_group(group)
+                        group.add_host(host)
+                        grouped_hosts.append(host)
+
                 if host not in grouped_hosts:
                     ungrouped.add_host(host)
+
+        # make sure ungrouped.hosts is the complement of grouped_hosts
+        ungrouped_hosts = [host for host in ungrouped.hosts if host not in grouped_hosts]

test/TestInventory.py

@@ -221,15 +221,14 @@ class TestInventory(unittest.TestCase):
     def test_yaml(self):
         inventory = self.yaml_inventory()
         hosts = inventory.list_hosts()
-        print hosts
-        expected_hosts=['jupiter', 'saturn', 'mars', 'zeus', 'hera', 'poseidon', 'thor', 'odin', 'loki']
+        expected_hosts=['garfield', 'goofy', 'hera', 'jerry', 'jupiter', 'loki', 'mars', 'mickey', 'odie', 'odin', 'poseidon', 'saturn', 'thor', 'tom', 'zeus']
         self.compare(hosts, expected_hosts)
 
     def test_yaml_all(self):
         inventory = self.yaml_inventory()
         hosts = inventory.list_hosts('all')
 
-        expected_hosts=['jupiter', 'saturn', 'mars', 'zeus', 'hera', 'poseidon', 'thor', 'odin', 'loki']
+        expected_hosts=['garfield', 'goofy', 'hera', 'jerry', 'jupiter', 'loki', 'mars', 'mickey', 'odie', 'odin', 'poseidon', 'saturn', 'thor', 'tom', 'zeus']
         self.compare(hosts, expected_hosts)
 
     def test_yaml_norse(self):
@@ -323,3 +322,29 @@ class TestInventory(unittest.TestCase):
         assert 'group_names' in vars
         assert sorted(vars['group_names']) == [ 'norse', 'ruler' ]
 
+    def test_yaml_some_animals(self):
+        inventory = self.yaml_inventory()
+        hosts = inventory.list_hosts("cat:mouse")
+        expected_hosts=['garfield', 'jerry', 'mickey', 'tom']
+        self.compare(hosts, expected_hosts)
+
+    def test_yaml_comic(self):
+        inventory = self.yaml_inventory()
+        hosts = inventory.list_hosts("comic")
+        expected_hosts=['garfield', 'odie']
+        self.compare(hosts, expected_hosts)
+
+    def test_yaml_orange(self):
+        inventory = self.yaml_inventory()
+        hosts = inventory.list_hosts("orange")
+        expected_hosts=['garfield', 'goofy']
+        self.compare(hosts, expected_hosts)
+
+    def test_yaml_garfield_vars(self):
+        inventory = self.yaml_inventory()
+        vars = inventory.get_variables('garfield')
+        assert vars == {'ears': 'pointy',
+                        'inventory_hostname': 'garfield',
+                        'group_names': ['cat', 'comic', 'orange'],
+                        'nose': 'pink'}
+ 

test/yaml_hosts

@@ -1,5 +1,7 @@
 ---
 
+# Below is the original way of defining hosts and groups.
+
 - jupiter
 - host: saturn
   vars:
@@ -37,3 +39,44 @@
 - group: multiple
   hosts:
   - saturn
+
+# Here we demonstrate that groups can be defined on a per-host basis.
+# When managing a large set of systems this format makes it easier to
+# ensure each of the systems is defined in a set of groups, compared
+# to the standard group definitions, where a host may need to be added
+# to multiple disconnected groups.
+
+- host: garfield
+  groups: [ comic, cat, orange ]
+  vars:
+  - nose: pink
+
+- host: odie
+  groups: [ comic, dog, yellow ]
+
+- host: mickey
+  groups: [ cartoon, mouse, red ]
+
+- host: goofy
+  groups: [ cartoon, dog, orange ]
+
+- host: tom
+  groups: [ cartoon, cat, gray ]
+
+- host: jerry
+  groups: [ cartoon, mouse, brown ]
+
+- group: cat
+  vars:
+  - ears: pointy
+  - nose: black
+
+- group: dog
+  vars:
+  - ears: flappy
+  - nose: black
+
+- group: mouse
+  vars:
+  - ears: round
+  - nose: black