Allow for changing the default merging strategy.

README.rst

@@ -231,6 +231,14 @@ The merging strategy can be set by including a dict in the form of:
 
  __: <merging strategy>
 
+If you want to use a different default merging strategy, you can do so in your
+salt master config:
+
+.. code:: yaml
+
+ pillarstack:
+ default_strategy: merge-first
+
 as the first item of the dict or list.
 This allows fine grained control over the merging process.
 

stack.py

@@ -36,20 +36,21 @@ def ext_pillar(minion_id, pillar, *args, **kwargs):
  if not isinstance(cfgs, list):
  cfgs = [cfgs]
  stack_config_files += cfgs
- for cfg in stack_config_files:
- if not os.path.isfile(cfg):
+ for cfg_path in stack_config_files:
+ if not os.path.isfile(cfg_path):
  log.info(
- 'Ignoring pillar stack cfg "%s": file does not exist', cfg)
+ 'Ignoring pillar stack cfg "%s": file does not exist', cfg_path)
  continue
- stack = _process_stack_cfg(cfg, stack, minion_id, pillar)
+ default_strategy = __opts__.get("pillarstack", {}).get("default_strategy", "merge-last")
+ stack = _process_stack_cfg(cfg_path, stack, minion_id, pillar, default_strategy)
  return stack
 
 
 def _to_unix_slashes(path):
  return posixpath.join(*path.split(os.sep))
 
 
-def _process_stack_cfg(cfg, stack, minion_id, pillar):
+def _process_stack_cfg(cfg, stack, minion_id, pillar, default_strategy):
  log.debug('Config: %s', cfg)
  basedir, filename = os.path.split(cfg)
  jenv = Environment(loader=FileSystemLoader(basedir), extensions=['jinja2.ext.do', salt.utils.jinja.SerializerExtension])
@@ -85,7 +86,7 @@ def _process_stack_cfg(cfg, stack, minion_id, pillar):
  log.info('Ignoring pillar stack template "%s": Can\'t parse '
  'as a valid yaml dictionary', path)
  continue
- stack = _merge_dict(stack, obj)
+ stack = _merge_dict(stack, obj, default_strategy)
  return stack
 
 
@@ -101,8 +102,8 @@ def _cleanup(obj):
  return obj
 
 
-def _merge_dict(stack, obj):
- strategy = obj.pop('__', 'merge-last')
+def _merge_dict(stack, obj, default_strategy="merge-last"):
+ strategy = obj.pop('__', default_strategy)
  if strategy not in strategies:
  raise Exception('Unknown strategy "{0}", should be one of {1}'.format(
  strategy, strategies))
@@ -120,22 +121,25 @@ def _merge_dict(stack, obj):
  stack_k = stack[k]
  stack[k] = _cleanup(v)
  v = stack_k
+ # Stop it getting double inverted later on.
+ if default_strategy == "merge-first":
+ default_strategy = "merge-last"
  if type(stack[k]) != type(v):
  log.debug('Force overwrite, types differ: \'%s\' != \'%s\'', stack[k], v)
  stack[k] = _cleanup(v)
  elif isinstance(v, dict):
- stack[k] = _merge_dict(stack[k], v)
+ stack[k] = _merge_dict(stack[k], v, default_strategy)
  elif isinstance(v, list):
- stack[k] = _merge_list(stack[k], v)
+ stack[k] = _merge_list(stack[k], v, default_strategy)
  else:
  stack[k] = v
  else:
  stack[k] = _cleanup(v)
  return stack
 
 
-def _merge_list(stack, obj):
- strategy = 'merge-last'
+def _merge_list(stack, obj, default_strategy="merge-last"):
+ strategy = default_strategy
  if obj and isinstance(obj[0], dict) and '__' in obj[0]:
  strategy = obj[0]['__']
  del obj[0]

test_stack.py

@@ -39,6 +39,85 @@ def test_merge(self):
  'INSTEAD OF =>', after_yml,
  ]))
 
+ def test_merge_first_explicit_top_level(self):
+ # This checks __ behaviour.
+ cur_stack = {
+ "flat": "First value",
+ "nested": {
+ "val": "First value nested",
+ "nested_again": {
+ "val": 123
+ }
+ }
+ }
+ obj = {
+ "__": "merge-first",
+ "flat": "Shouldn't overwrite",
+ "flat_newval": "OK",
+ "nested": {
+ "val": "Shouldn't overwrite",
+ "newval": "OK",
+ "nested_again": {
+ "val": 456,
+ "newval": 678
+ }
+ }
+ }
+ expected = {
+ "flat": "First value",
+ "flat_newval": "OK",
+ "nested": {
+ "val": "First value nested",
+ "newval": "OK",
+ "nested_again": {
+ "val": 123,
+ "newval": 678
+ }
+ }
+ }
+ new_stack = stack._merge_dict(cur_stack, obj)
+ self.assertDictEqual(new_stack, expected)
+
+ def test_merge_first_with_default(self):
+ # This makes sure that we get the same effect as
+ # test_merge_first_explicit_top_level, but using
+ # default_strategy instead.
+ cur_stack = {
+ "flat": "First value",
+ "nested": {
+ "val": "First value nested",
+ "nested_again": {
+ "val": 123
+ }
+ }
+ }
+ obj = {
+ "flat": "Shouldn't overwrite",
+ "flat_newval": "OK",
+ "nested": {
+ "val": "Shouldn't overwrite",
+ "newval": "OK",
+ "nested_again": {
+ "val": 456,
+ "newval": 678
+ }
+ }
+ }
+ expected = {
+ "flat": "First value",
+ "flat_newval": "OK",
+ "nested": {
+ "val": "First value nested",
+ "newval": "OK",
+ "nested_again": {
+ "val": 123,
+ "newval": 678
+ }
+ }
+ }
+ new_stack = stack._merge_dict(cur_stack, obj, default_strategy="merge-first")
+ self.assertDictEqual(new_stack, expected)
+
 
 if __name__ == '__main__':
  unittest.main()