Implement __fspath__ a bit more smart: return the wrapped if str/bytes and return wrapped if it doesn't have any __fspath__ method.

Author: ionelmc

src/lazy_object_proxy/cext.c

@@ -222,6 +222,31 @@ static PyObject *Proxy_str(ProxyObject *self)
 
 /* ------------------------------------------------------------------------- */
 
+static PyObject *Proxy_fspath(ProxyObject *self)
+{
+    _Py_IDENTIFIER(__fspath__);
+    Proxy__ENSURE_WRAPPED_OR_RETURN_NULL(self);
+    PyObject *func = NULL;
+    PyObject *fspath = NULL;
+
+    if (PyUnicode_Check(self->wrapped) || PyBytes_Check(self->wrapped)) {
+        Py_INCREF(self->wrapped);
+        return self->wrapped;
+    }
+
+    func = _PyObject_LookupSpecial(self->wrapped, &PyId___fspath__);
+    if (NULL == func) {
+        Py_INCREF(self->wrapped);
+        return self->wrapped;
+    }
+
+    fspath = PyObject_CallFunctionObjArgs(func, NULL);
+    Py_DECREF(func);
+    return fspath;
+}
+
+/* ------------------------------------------------------------------------- */
+
 static PyObject *Proxy_add(PyObject *o1, PyObject *o2)
 {
     Proxy__WRAPPED_REPLACE_OR_RETURN_NULL(o1);
@@ -1282,7 +1307,7 @@ static PyMethodDef Proxy_methods[] = {
     { "__reversed__", (PyCFunction)Proxy_reversed, METH_NOARGS, 0 },
     { "__reduce__", (PyCFunction)Proxy_reduce, METH_NOARGS, 0 },
     { "__reduce_ex__", (PyCFunction)Proxy_reduce, METH_O, 0 },
-    { "__fspath__", (PyCFunction)Proxy_str, METH_NOARGS, 0 },
+    { "__fspath__", (PyCFunction)Proxy_fspath, METH_NOARGS, 0 },
 #if PY_MAJOR_VERSION >= 3
     { "__round__",  (PyCFunction)Proxy_round, METH_NOARGS, 0 },
 #endif

src/lazy_object_proxy/simple.py

@@ -5,6 +5,7 @@
 from .compat import with_metaclass
 from .utils import cached_property
 from .utils import identity
+from .utils import string_types
 
 
 def make_proxy_method(code):
@@ -100,7 +101,17 @@ def __repr__(self, __getattr__=object.__getattribute__):
                 self.__factory__
             )
 
-    __fspath__ = make_proxy_method(str)
+    def __fspath__(self):
+        wrapped = self.__wrapped__
+        if isinstance(wrapped, string_types):
+            return wrapped
+        else:
+            fspath = getattr(wrapped, '__fspath__', None)
+            if fspath is None:
+                return wrapped
+            else:
+                return fspath()
+
     __reversed__ = make_proxy_method(reversed)
 
     if PY3:

src/lazy_object_proxy/slots.py

@@ -4,6 +4,7 @@
 from .compat import PY3
 from .compat import with_metaclass
 from .utils import identity
+from .utils import string_types
 
 
 class _ProxyMethods(object):
@@ -153,7 +154,15 @@ def __repr__(self, __getattr__=object.__getattribute__):
             )
 
     def __fspath__(self):
-        return str(self.__wrapped__)
+        wrapped = self.__wrapped__
+        if isinstance(wrapped, string_types):
+            return wrapped
+        else:
+            fspath = getattr(wrapped, '__fspath__', None)
+            if fspath is None:
+                return wrapped
+            else:
+                return fspath()
 
     def __reversed__(self):
         return reversed(self.__wrapped__)

src/lazy_object_proxy/utils.py

@@ -1,3 +1,13 @@
+import sys
+
+PY3 = sys.version_info[0] == 3
+
+if PY3:
+    string_types = str, bytes
+else:
+    string_types = basestring,
+
+
 def identity(obj):
     return obj
 

tests/test_lazy_object_proxy.py

@@ -1946,6 +1946,19 @@ def __init__(self, func, **lazy_attr):
     assert not called
 
 
+class FSPathMock(object):
+    def __fspath__(self):
+        return '/tmp'
+
+
 @pytest.mark.skipif(not hasattr(os, "fspath"), reason="No os.fspath support.")
 def test_fspath(lazy_object_proxy):
     assert os.fspath(lazy_object_proxy.Proxy(lambda: '/tmp')) == '/tmp'
+    assert os.fspath(lazy_object_proxy.Proxy(FSPathMock)) == '/tmp'
+    with pytest.raises(TypeError) as excinfo:
+        os.fspath(lazy_object_proxy.Proxy(lambda: None))
+    assert '__fspath__() to return str or bytes, not NoneType' in excinfo.value.args[0]
+
+
+def test_fspath_method(lazy_object_proxy):
+    assert lazy_object_proxy.Proxy(FSPathMock).__fspath__() == '/tmp'