Rewritten dcd.cfg.Config

Config now supports full hierarchical and overlay-capable usage.
A generic tree overlay function is in aux.

dcd/cfg.py

@@ -4,6 +4,18 @@
 import jsmin
 import json
 
+from . import aux
+
+def _read_json(path):
+	"""
+	Reads a data structure from a JSON file pointed to by `path`.
+	
+	Removes any C/JS-like comments from it.
+	"""
+	
+	with open(path) as f:
+		return json.loads(jsmin.jsmin(f.read()))
+
 class Config:
 	"""
 	A hierarchical key-value container that can be loaded from JSON or a Python dict.
@@ -11,48 +23,30 @@ class Config:
 	Any contained dicts are automatically converted to Config instances as well.
 	
 	Supports sequential overwriting - so one can load a default config and then
-	progressively overwrite it with overlays:
-	
-	
-	
-	
-	
-	
-	
-	>>> raw
-{'a': 1, 'b': {'ba': 2, 'bb': 3, 'bc': {'bca': None}}, 'c': 4}
->>> overlay
-{'b': {'bc': {'bca': 42}}}
-
-	
-	
-	while stack:
-	current = stack[-1]
-	
-	...
-	
-	stack.pop()
-
-for key in overlay.keys():
-	
-	
+	progressively overlay more on top:
 	
+	>>> c = Config.from_file("/usr/lib/app/default.cfg")
+	>>> c.update_from_file("/etc/app/config.cfg")
+	>>> c.update({"key", value, "subtree": {"key": "value"}})
 	"""
 	
-	def __init__(self, d, readonly=False):
+	def __init__(self, d=None, readonly=False):
+		if d is None:
+			d = {}
+		
 		assert type(d) == dict
 		object.__setattr__(self, "raw", d)
 		object.__setattr__(self, "readonly", readonly)
 	
 	@classmethod
 	def from_file(cls, path, readonly=False):
-		with open(path) as f:
-			initial = json.loads(jsmin.jsmin(f.read()))
-		
-		return cls(initial, readonly)
+		return cls(_read_json(path), readonly)
 	
 	def update(self, d):
-		
+		aux.overlay_tree(self.raw, d)
+	
+	def update_from_file(self, path):
+		self.update(_read_json(path))
 	
 	def keys(self):
 		return self.raw.keys()