Merge pull request #1903 from leucos/mergeable-hash-vars

Adds user-selectable hash merging support in vars

examples/ansible.cfg

@@ -76,6 +76,16 @@ remote_port=22
 
 sudo_exe=sudo
 
+# how to handle hash defined in several places
+# hash can be merged, or replaced
+# if you use replace, and have multiple hashes named 'x', the last defined
+# will override the previously defined one
+# if you use merge here, hash will cumulate their keys, but keys will still
+# override each other
+# replace is the default value, and is how ansible always handled hash variables
+#
+# hash_behaviour=replace
+
 # if set, always use this private key file for authentication, same as if passing
 # --private-key to ansible or ansible-playbook
 

lib/ansible/constants.py

@@ -92,6 +92,7 @@ DEFAULT_MANAGED_STR       = get_config(p, DEFAULTS, 'ansible_managed',  None,
 DEFAULT_SYSLOG_FACILITY   = get_config(p, DEFAULTS, 'syslog_facility',  'ANSIBLE_SYSLOG_FACILITY', 'LOG_USER')
 DEFAULT_KEEP_REMOTE_FILES = get_config(p, DEFAULTS, 'keep_remote_files', 'ANSIBLE_KEEP_REMOTE_FILES', '0')
 DEFAULT_SUDO_EXE          = get_config(p, DEFAULTS, 'sudo_exe', 'ANSIBLE_SUDO_EXE', 'sudo')
+DEFAULT_HASH_BEHAVIOUR    = get_config(p, DEFAULTS, 'hash_behaviour', 'ANSIBLE_HASH_BEHAVIOUR', 'replace')
 
 DEFAULT_ACTION_PLUGIN_PATH     = shell_expand_path(get_config(p, DEFAULTS, 'action_plugins',     None, '/usr/share/ansible_plugins/action_plugins'))
 DEFAULT_CALLBACK_PLUGIN_PATH   = shell_expand_path(get_config(p, DEFAULTS, 'callback_plugins',   None, '/usr/share/ansible_plugins/callback_plugins'))

lib/ansible/inventory/vars_plugins/group_vars.py

@@ -19,6 +19,7 @@ import os
 import glob
 from ansible import errors
 from ansible import utils
+import ansible.constants as C
 
 class VarsModule(object):
 
@@ -48,7 +49,11 @@ class VarsModule(object):
                 data = utils.parse_yaml_from_file(path)
                 if type(data) != dict:
                     raise errors.AnsibleError("%s must be stored as a dictionary/hash" % path)
-                results.update(data)
+                if C.DEFAULT_HASH_BEHAVIOUR == "merge":
+                    # let data content override results if needed
+                    results = utils.merge_hash(results, data)
+                else:
+                    results.update(data)
 
         # load vars in playbook_dir/group_vars/name_of_host
         path = os.path.join(basedir, "host_vars/%s" % host.name)
@@ -56,7 +61,10 @@ class VarsModule(object):
             data = utils.parse_yaml_from_file(path)
             if type(data) != dict:
                 raise errors.AnsibleError("%s must be stored as a dictionary/hash" % path)
-            results.update(data)
-
+            if C.DEFAULT_HASH_BEHAVIOUR == "merge":
+                # let data content override results if needed
+                results = utils.merge_hash(results, data)
+            else:
+                results.update(data)
         return results
 

lib/ansible/utils/__init__.py

@@ -19,6 +19,7 @@ import sys
 import os
 import shlex
 import yaml
+import copy
 import optparse
 import operator
 from ansible import errors
@@ -273,6 +274,26 @@ def parse_kv(args):
                 options[k]=v
     return options
 
+def merge_hash(a, b):
+    ''' merges hash b into a
+    this means that if b has key k, the resulting has will have a key k
+    which value comes from b
+    said differently, all key/value combination from b will override a's '''
+
+    # and iterate over b keys
+    for k, v in b.iteritems():
+        if k in a and isinstance(a[k], dict):
+            # if this key is a hash and exists in a
+            # we recursively call ourselves with 
+            # the key value of b
+            a[k] = merge_hash(a[k], v)
+        else:
+            # k is not in a, no need to merge b, we just deecopy
+            # or k is not a dictionnary, no need to merge b either, we just deecopy it
+            a[k] = v
+    # finally, return the resulting hash when we're done iterating keys
+    return a
+
 def md5s(data):
     ''' Return MD5 hex digest of data. '''