Implement property attributes and functions

Author: skinnyBat

tests/snippets/property.py

@@ -30,3 +30,18 @@ def foo(self):
 
 with assertRaises(TypeError):
     property.__new__(object)
+
+
+p1 = property("a", "b", "c")
+
+assert p1.fget == "a"
+assert p1.fset == "b"
+assert p1.fdel == "c"
+
+assert p1.getter(1).fget == 1
+assert p1.setter(2).fset == 2
+assert p1.deleter(3).fdel == 3
+
+assert p1.getter(None).fget == "a"
+assert p1.setter(None).fset == "b"
+assert p1.deleter(None).fdel == "c"

vm/src/obj/objnone.rs

@@ -21,6 +21,15 @@ impl IntoPyObject for () {
     }
 }
 
+impl<T: IntoPyObject> IntoPyObject for Option<T> {
+    fn into_pyobject(self, ctx: &PyContext) -> PyResult {
+        match self {
+            Some(x) => x.into_pyobject(ctx),
+            None => Ok(ctx.none()),
+        }
+    }
+}
+
 impl PyNoneRef {
     fn repr(self, _vm: &mut VirtualMachine) -> PyResult<String> {
         Ok("None".to_string())

vm/src/obj/objproperty.rs

@@ -67,6 +67,8 @@ impl PyPropertyRef {
         )
     }
 
+    // Descriptor methods
+
     fn get(self, obj: PyObjectRef, _owner: PyClassRef, vm: &mut VirtualMachine) -> PyResult {
         if let Some(getter) = self.getter.as_ref() {
             vm.invoke(getter.clone(), obj)
@@ -90,6 +92,58 @@ impl PyPropertyRef {
             Err(vm.new_attribute_error("can't delete attribute".to_string()))
         }
     }
+
+    // Access functions
+
+    fn fget(self, _vm: &mut VirtualMachine) -> Option<PyObjectRef> {
+        self.getter.clone()
+    }
+
+    fn fset(self, _vm: &mut VirtualMachine) -> Option<PyObjectRef> {
+        self.setter.clone()
+    }
+
+    fn fdel(self, _vm: &mut VirtualMachine) -> Option<PyObjectRef> {
+        self.deleter.clone()
+    }
+
+    // Python builder functions
+
+    fn getter(self, getter: Option<PyObjectRef>, vm: &mut VirtualMachine) -> PyResult<Self> {
+        Self::new_with_type(
+            vm,
+            PyProperty {
+                getter: getter.or_else(|| self.getter.clone()),
+                setter: self.setter.clone(),
+                deleter: self.deleter.clone(),
+            },
+            self.typ(),
+        )
+    }
+
+    fn setter(self, setter: Option<PyObjectRef>, vm: &mut VirtualMachine) -> PyResult<Self> {
+        Self::new_with_type(
+            vm,
+            PyProperty {
+                getter: self.getter.clone(),
+                setter: setter.or_else(|| self.setter.clone()),
+                deleter: self.deleter.clone(),
+            },
+            self.typ(),
+        )
+    }
+
+    fn deleter(self, deleter: Option<PyObjectRef>, vm: &mut VirtualMachine) -> PyResult<Self> {
+        Self::new_with_type(
+            vm,
+            PyProperty {
+                getter: self.getter.clone(),
+                setter: self.setter.clone(),
+                deleter: deleter.or_else(|| self.deleter.clone()),
+            },
+            self.typ(),
+        )
+    }
 }
 
 pub struct PropertyBuilder<'a, T> {
@@ -190,5 +244,13 @@ pub fn init(context: &PyContext) {
         "__get__" => context.new_rustfunc(PyPropertyRef::get),
         "__set__" => context.new_rustfunc(PyPropertyRef::set),
         "__delete__" => context.new_rustfunc(PyPropertyRef::delete),
+
+        "fget" => context.new_property(PyPropertyRef::fget),
+        "fset" => context.new_property(PyPropertyRef::fset),
+        "fdel" => context.new_property(PyPropertyRef::fdel),
+
+        "getter" => context.new_rustfunc(PyPropertyRef::getter),
+        "setter" => context.new_rustfunc(PyPropertyRef::setter),
+        "deleter" => context.new_rustfunc(PyPropertyRef::deleter),
     });
 }

vm/src/pyobject.rs

@@ -745,6 +745,13 @@ impl<T: PyValue> PyRef<T> {
     pub fn into_object(self) -> PyObjectRef {
         self.obj
     }
+
+    pub fn typ(&self) -> PyClassRef {
+        PyRef {
+            obj: self.obj.typ(),
+            _payload: PhantomData,
+        }
+    }
 }
 
 impl<T> Deref for PyRef<T>
@@ -1211,6 +1218,16 @@ impl TryFromObject for PyObjectRef {
     }
 }
 
+impl<T: TryFromObject> TryFromObject for Option<T> {
+    fn try_from_object(vm: &mut VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
+        if vm.get_none().is(&obj) {
+            Ok(None)
+        } else {
+            T::try_from_object(vm, obj).map(|x| Some(x))
+        }
+    }
+}
+
 /// A map of keyword arguments to their values.
 ///
 /// A built-in function with a `KwArgs` parameter is analagous to a Python
@@ -1389,12 +1406,6 @@ where
     }
 }
 
-// TODO: Allow a built-in function to return an `Option`, i.e.:
-//
-//     impl<T: IntoPyObject> IntoPyObject for Option<T>
-//
-// Option::None should map to a Python `None`.
-
 // Allows a built-in function to return any built-in object payload without
 // explicitly implementing `IntoPyObject`.
 impl<T> IntoPyObject for T