Make property_available_if a read-only property

sksurv/__init__.py

@@ -6,7 +6,7 @@
 from sklearn.pipeline import Pipeline, _final_estimator_has
 from sklearn.utils.metaestimators import available_if
 
-from .util import conditionalAvailableProperty
+from .util import property_available_if
 
 
 def _get_version(name):
@@ -127,7 +127,7 @@ def predict_survival_function(self, X, **kwargs):
     return self.steps[-1][-1].predict_survival_function(Xt, **kwargs)
 
 
-@conditionalAvailableProperty(_final_estimator_has('_predict_risk_score'))
+@property_available_if(_final_estimator_has("_predict_risk_score"))
 def _predict_risk_score(self):
     return self.steps[-1][-1]._predict_risk_score
 

sksurv/util.py

@@ -261,82 +261,61 @@ def safe_concat(objs, *args, **kwargs):
     return concatenated
 
 
-class _ConditionalAvailableProperty:
+class _PropertyAvailableIfDescriptor:
     """Implements a conditional property using the descriptor protocol based on the property decorator.
 
-    The corresponding class in scikit-learn (_AvailableIfDescriptor) only supports callables. This
-    class adopts the property decorator as presented by the descriptor guide in the offical documentation.
+    The corresponding class in scikit-learn (`_AvailableIfDescriptor`) only supports callables.
+    This class adopts the property decorator as described in the descriptor guide in the offical Python documentation.
 
-    The check is defined on the getter function. Setter, Deleter also need to be defined on the exposing clas
-s
-    if they are supposed to be available.
-
-    See Also
+    See also
     --------
-    sklearn.utils.available_if._AvailableIfDescriptor:
-    The original class in scikit-learn.
+    https://docs.python.org/3/howto/descriptor.html
+        Descriptor HowTo Guide
+
+    :class:`sklearn.utils.available_if._AvailableIfDescriptor`
+        The original class in scikit-learn.
     """
 
-    def __init__(self, check, fget=None, fset=None, fdel=None, doc=None):
-        self._check = check
+    def __init__(self, check, fget, doc=None):
+        self.check = check
         self.fget = fget
-        self.fset = fset
-        self.fdel = fdel
         if doc is None and fget is not None:
             doc = fget.__doc__
         self.__doc__ = doc
-        self._name = ''
-
-    def _run_check(self, obj):
-        attr_err = AttributeError(
-            f"This {repr(obj)} has no attribute {repr(self._name)}"
-        )
-        if not self.check(obj):
-            raise attr_err
+        self._name = ""
 
     def __set_name__(self, owner, name):
         self._name = name
 
     def __get__(self, obj, objtype=None):
         if obj is None:
             return self
-        self._run_check(obj)
+
+        attr_err = AttributeError(f"This {obj!r} has no attribute {self._name!r}")
+        if not self.check(obj):
+            raise attr_err
+
         if self.fget is None:
             raise AttributeError(f"property '{self._name}' has no getter")
         return self.fget(obj)
 
-    def __set__(self, obj, value):
-        self._run_check(obj)
-        if self.fset is None:
-            raise AttributeError(f"property '{self._name}' has no setter")
-        self.fset(obj, value)
-
-    def __delete__(self, obj):
-        self._run_check(obj)
-        if self.fdel is None:
-            raise AttributeError(f"property '{self._name}' has no deleter")
-        self.fdel(obj)
-
-    @property
-    def check(self):
-        return self._check
-
-    def getter(self, fget):
-        prop = type(self)(self.check, fget, self.fset, self.fdel, self.__doc__)
-        prop._name = self._name
-        return prop
-
-    def setter(self, fset):
-        prop = type(self)(self.check, self.fget, fset, self.fdel, self.__doc__)
-        prop._name = self._name
-        return prop
-
-    def deleter(self, fdel):
-        prop = type(self)(self.check, self.fget, self.fset, fdel, self.__doc__)
-        prop._name = self._name
-        return prop
-
-
-def conditionalAvailableProperty(check):
-    prop = _ConditionalAvailableProperty(check=check)
-    return prop.getter
+
+def property_available_if(check):
+    """A property attribute that is available only if check returns a truthy value.
+
+    Only supports getting an attribute value, setting or deleting an attribute value are not supported.
+
+    Parameters
+    ----------
+    check : callable
+        When passed the object of the decorated method, this should return
+        `True` if the property attribute is available, and either return `False`
+        or raise an `AttributeError` if not available.
+
+    Returns
+    -------
+    callable
+        Callable makes the decorated property available if `check` returns
+        `True`, otherwise the decorated property is unavailable.
+    """
+    return lambda fn: _PropertyAvailableIfDescriptor(check=check, fget=fn)

tests/test_util.py

@@ -8,7 +8,7 @@
 import pytest
 
 from sksurv.testing import FixtureParameterFactory
-from sksurv.util import Surv, conditionalAvailableProperty, safe_concat
+from sksurv.util import Surv, _PropertyAvailableIfDescriptor, property_available_if, safe_concat
 
 
 class ConcatCasesFactory(FixtureParameterFactory):
@@ -377,17 +377,11 @@ def __init__(self, val):
             self.avail = False
             self._prop = val
 
-        @conditionalAvailableProperty(lambda self: self.avail)
+        @property_available_if(lambda self: self.avail)
         def prop(self):
             return self._prop
 
-        @prop.setter
-        def prop(self, new):
-            self._prop = new
-
-        @prop.deleter
-        def prop(self):
-            self.avail = False
+        no_prop = _PropertyAvailableIfDescriptor(lambda self: self.avail, fget=None)
 
     testval = 43
     msg = "has no attribute 'prop'"
@@ -397,30 +391,15 @@ def prop(self):
     test_obj = WithCondProp(testval)
     with pytest.raises(AttributeError, match=msg):
         _ = test_obj.prop
-    with pytest.raises(AttributeError, match=msg):
-        test_obj.prop = testval - 1
-    with pytest.raises(AttributeError, match=msg):
-        del test_obj.prop
+    assert test_obj.avail is False
+
     test_obj.avail = True
     assert test_obj.prop == testval
-    test_obj.prop = testval - 2
-    assert test_obj.prop == testval - 2
-    del test_obj.prop
-    assert test_obj.avail is False
+
+    test_obj.avail = False
     with pytest.raises(AttributeError, match=msg):
         _ = test_obj.prop
-    with pytest.raises(AttributeError, match=msg):
-        test_obj.prop = testval - 3
-    with pytest.raises(AttributeError, match=msg):
-        del test_obj.prop
 
     test_obj.avail = True
-    WithCondProp.prop.fget = None
     with pytest.raises(AttributeError, match="has no getter"):
-        _ = test_obj.prop
-    WithCondProp.prop.fset = None
-    with pytest.raises(AttributeError, match="has no setter"):
-        test_obj.prop = testval - 4
-    WithCondProp.prop.fdel = None
-    with pytest.raises(AttributeError, match="has no deleter"):
-        del test_obj.prop
+        _ = test_obj.no_prop