chg: dev: force YAML C ``libyaml`` bindings for python merging code

bin/compose-core

@@ -134,6 +134,16 @@ export _merge_yaml_common_code="
 import sys
 import yaml
 
+try:
+    from yaml import CSafeLoader as SafeLoader, CSafeDumper as SafeDumper
+except ImportError:  ## pragma: no cover
+    sys.stderr.write('YAML code in pure python\n')
+    exit(1)
+    from yaml import SafeLoader, SafeDumper
+
+class MySafeLoader(SafeLoader): pass
+class MySafeDumper(SafeDumper): pass
+
 
 try:
     # included in standard lib from Python 2.7
@@ -149,13 +159,50 @@ except ImportError:
 class MyOrderedDict(OrderedDict):
     pass
 
-yaml.add_representer(
+MySafeDumper.add_representer(
     MyOrderedDict,
     lambda cls, data: cls.represent_dict(data.items()))
 
-yaml.add_constructor(
+
+def construct_omap(cls, node):
+    cls.flatten_mapping(node)
+    return MyOrderedDict(cls.construct_pairs(node))
+
+
+MySafeLoader.add_constructor(
     yaml.resolver.BaseResolver.DEFAULT_MAPPING_TAG,
-    lambda cls, node: MyOrderedDict(cls.construct_pairs(node)))
+    construct_omap)
+
+
+##
+## Support local and global objects
+##
+
+class EncapsulatedNode(object): pass
+
+
+def mk_encapsulated_node(s, node):
+
+    method = 'construct_%s' % (node.id, )
+    data = getattr(s, method)(node)
+
+    class _E(data.__class__, EncapsulatedNode):
+        pass
+
+    _E.__name__ = str(node.tag)
+    _E._node = node
+    return _E(data)
+
+
+def represent_encapsulated_node(s, o):
+    value = s.represent_data(o.__class__.__bases__[0](o))
+    value.tag = o.__class__.__name__
+    return value
+
+
+MySafeDumper.add_multi_representer(EncapsulatedNode,
+                                       represent_encapsulated_node)
+MySafeLoader.add_constructor(None, mk_encapsulated_node)
 
 
 def fc(filename):
@@ -218,7 +265,7 @@ def merge_cli(*args):
                          for i, a in enumerate(e.args[2]))))
         exit(1)
     if c is not None:
-        print '%s' % yaml.dump(c, default_flow_style=False)
+        print '%s' % yaml.dump(c, default_flow_style=False, Dumper=MySafeDumper)
 
 "
 
@@ -230,7 +277,7 @@ merge_yaml() {
 
 $_merge_yaml_common_code
 
-merge_cli(*(yaml.load(fc(f)) for f in sys.argv[1:]))
+merge_cli(*(yaml.load(fc(f), Loader=MySafeLoader) for f in sys.argv[1:]))
 EOF
     fi
 
@@ -247,7 +294,7 @@ merge_yaml_str() {
 
 $_merge_yaml_common_code
 
-merge_cli(*(yaml.load(f) for f in sys.argv[1:]))
+merge_cli(*(yaml.load(f, Loader=MySafeLoader) for f in sys.argv[1:]))
 EOF
     fi
 
@@ -264,9 +311,14 @@ yaml_key_val_str() {
 
 $_merge_yaml_common_code
 
-print '%s' % yaml.dump({
-    yaml.load(sys.argv[1]):
-    yaml.load(sys.argv[2])}, default_flow_style=False)
+print '%s' % yaml.dump(
+  {
+    yaml.load(sys.argv[1], Loader=MySafeLoader):
+    yaml.load(sys.argv[2], Loader=MySafeLoader)
+  },
+  default_flow_style=False,
+  Dumper=MySafeDumper,
+  )
 
 EOF
     fi