Merge pull request #95 from michaelbynum/immutable-config

Adding an ImmutableConfigValue class

pyutilib/misc/config.py

@@ -1068,6 +1068,63 @@ def _data_collector(self, level, prefix, visibility=None, docMode=False):
         yield (level, prefix, self, self)
 
 
+class ImmutableConfigValue(ConfigValue):
+    def set_value(self, value):
+        if self._cast(value) != self._data:
+            raise RuntimeError(str(self) + ' is currently immutable')
+        super(ImmutableConfigValue, self).set_value(value)
+
+    def reset(self):
+        try:
+            super(ImmutableConfigValue, self).set_value(self._default)
+        except:
+            if hasattr(self._default, '__call__'):
+                super(ImmutableConfigValue, self).set_value(self._default())
+            else:
+                raise
+        self._userAccessed = False
+        self._userSet = False
+
+
+class MarkImmutable(object):
+    """
+    Mark instances of ConfigValue as immutable.
+
+    Parameters
+    ----------
+    config_value: ConfigValue
+        The ConfigValue instances that should be marked immutable. 
+        Note that multiple instances of ConfigValue can be passed.
+
+    Examples
+    --------
+    >>> config = ConfigBlock()
+    >>> config.declare('a', ConfigValue(default=1, domain=int))
+    >>> config.declare('b', ConfigValue(default=1, domain=int))
+    >>> locker = MarkImmutable(config.get('a'), config.get('b'))
+    
+    Now, config.a and config.b cannot be changed. To make them mutable again, 
+
+    >>> locker.release_lock()
+    """
+    def __init__(self, *args):
+        self._locked = list()
+        try:
+            for arg in args:
+                if type(arg) is not ConfigValue:
+                    raise ValueError('Only ConfigValue instances can be marked immutable.')
+                arg.__class__ = ImmutableConfigValue
+                self._locked.append(arg)
+        except:
+            self.release_lock()
+            raise
+
+    def release_lock(self):
+        for arg in self._locked:
+            arg.__class__ = ConfigValue
+        self._locked = list()
+
+
 class ConfigList(ConfigBase):
     """Store and manipulate a list of configuration values.
 

pyutilib/misc/tests/test_config.py

@@ -17,7 +17,7 @@
 import pyutilib.th as unittest
 
 import pyutilib.misc.comparison
-from pyutilib.misc.config import ConfigValue, ConfigBlock, ConfigList
+from pyutilib.misc.config import ConfigValue, ConfigBlock, ConfigList, MarkImmutable
 
 from six import PY3, StringIO
 
@@ -39,6 +39,49 @@ def _display(obj, *args):
     obj.display(ostream=test, *args)
     return test.getvalue()
 
+
+class TestImmutableConfigValue(unittest.TestCase):
+    def test_immutable_config_value(self):
+        config = ConfigBlock()
+        config.declare('a', ConfigValue(default=1, domain=int))
+        config.declare('b', ConfigValue(default=1, domain=int))
+        config.a = 2
+        config.b = 3
+        self.assertEqual(config.a, 2)
+        self.assertEqual(config.b, 3)
+        locker = MarkImmutable(config.get('a'), config.get('b'))
+        with self.assertRaises(Exception):
+            config.a = 4
+        with self.assertRaises(Exception):
+            config.b = 5
+        config.a = 2
+        config.b = 3
+        self.assertEqual(config.a, 2)
+        self.assertEqual(config.b, 3)
+        locker.release_lock()
+        config.a = 4
+        config.b = 5
+        self.assertEqual(config.a, 4)
+        self.assertEqual(config.b, 5)
+        with self.assertRaises(ValueError):
+            locker = MarkImmutable(config.get('a'), config.b)
+        self.assertEqual(type(config.get('a')), ConfigValue)
+        config.a = 6
+        self.assertEqual(config.a, 6)
+
+        config.declare('c', ConfigValue(default=-1, domain=int))
+        locker = MarkImmutable(config.get('a'), config.get('b'))
+        config2 = config({'c': -2})
+        self.assertEqual(config2.a, 6)
+        self.assertEqual(config2.b, 5)
+        self.assertEqual(config2.c, -2)
+        with self.assertRaises(Exception):
+            config3 = config({'a': 1})
+        locker.release_lock()
+        config3 = config({'a': 1})
+        self.assertEqual(config3.a, 1)
+
+
 class Test(unittest.TestCase):
 
     def setUp(self):