options: defaults are a class attribute

2 files changed, 23 insertions, 10 deletions

diff --git a/mitmproxy/optmanager.py b/mitmproxy/optmanager.py
index 3ce76a45..304f5129 100644
--- a/mitmproxy/optmanager.py
+++ b/mitmproxy/optmanager.py
@@ -14,7 +14,20 @@ from mitmproxy.utils import typecheck
 """
 
 
-class OptManager:
+class _DefaultsMeta(type):
+    def __new__(cls, name, bases, namespace, **kwds):
+        ret = type.__new__(cls, name, bases, dict(namespace))
+        defaults = {}
+        for klass in reversed(inspect.getmro(ret)):
+            for p in inspect.signature(klass.__init__).parameters.values():
+                if p.kind in (p.KEYWORD_ONLY, p.POSITIONAL_OR_KEYWORD):
+                    if not p.default == p.empty:
+                        defaults[p.name] = p.default
+        ret._defaults = defaults
+        return ret
+
+
+class OptManager(metaclass=_DefaultsMeta):
     """
         OptManager is the base class from which Options objects are derived.
         Note that the __init__ method of all child classes must force all
@@ -37,15 +50,6 @@ class OptManager:
         # ._initialized = True as the final operation.
         instance = super().__new__(cls)
         instance.__dict__["_opts"] = {}
-
-        defaults = {}
-        for klass in reversed(inspect.getmro(cls)):
-            for p in inspect.signature(klass.__init__).parameters.values():
-                if p.kind in (p.KEYWORD_ONLY, p.POSITIONAL_OR_KEYWORD):
-                    if not p.default == p.empty:
-                        defaults[p.name] = p.default
-        instance.__dict__["_defaults"] = defaults
-
         return instance
 
     def __init__(self):
@@ -122,6 +126,10 @@ class OptManager:
         """
         self.update(**self._defaults)
 
+    @classmethod
+    def default(klass, opt):
+        return copy.deepcopy(klass._defaults[opt])
+
     def update(self, **kwargs):
         updated = set(kwargs.keys())
         for k, v in kwargs.items():
diff --git a/test/mitmproxy/test_optmanager.py b/test/mitmproxy/test_optmanager.py
index c7808391..385cf621 100644
--- a/test/mitmproxy/test_optmanager.py
+++ b/test/mitmproxy/test_optmanager.py
@@ -28,6 +28,11 @@ class TD2(TD):
 
 
 def test_defaults():
+    assert TD2.default("one") == "done"
+    assert TD2.default("two") == "dtwo"
+    assert TD2.default("three") == "dthree"
+    assert TD2.default("four") == "dfour"
+
     o = TD2()
     assert o._defaults == {
         "one": "done",