gistfile1.py

diff --git a/scrapy/selector/unified.py b/scrapy/selector/unified.py
index b8a3678..28d8ac9 100644
--- a/scrapy/selector/unified.py
+++ b/scrapy/selector/unified.py
@@ -46,6 +46,38 @@ def _response_from_text(text, st):
               body=unicode_to_str(text, 'utf-8'))
 
 
+class SelectorContext(object):
+
+    def __init__(self):
+        self.stack = []
+
+    def open(self, selector):
+        self.stack.append(selector)
+
+    def close(self):
+        self.stack.pop()
+
+    def get_active(self):
+        if self.stack:
+            return self.stack[-1]
+
+selector_context = SelectorContext()
+
+
+from functools import wraps
+
+
+def selectorcontext(func):
+    @wraps(func)
+    def wrapper(**kwargs):
+        if 'selector' not in kwargs:
+            selector = selector_context.get_active()
+            if selector is not None:
+                kwargs['selector'] = selector
+        return func(**kwargs)
+    return wrapper
+
+
 class Selector(object_ref):
 
     __slots__ = ['response', 'text', 'namespaces', 'type', '_expr', '_root',
@@ -85,6 +117,13 @@ class Selector(object_ref):
         self._root = _root
         self._expr = _expr
 
+    def __enter__(self):
+        selector_context.open(self)
+        return self
+
+    def __exit__(self, type, value, traceback):
+        selector_context.close()
+
     def xpath(self, query):
         try:
             xpathev = self._root.xpath
@@ -166,7 +205,17 @@ class SelectorList(list):
     def __getslice__(self, i, j):
         return self.__class__(list.__getslice__(self, i, j))
 
+    def __enter__(self):
+        selector_context.open(self)
+        return self
+
+    def __exit__(self, type, value, traceback):
+        selector_context.close()
+
     def xpath(self, xpath):
+        selector = selector_context.get_active()
+        if selector:
+            return selector.xpath(xpath)
         return self.__class__(flatten([x.xpath(xpath) for x in self]))
 
     def css(self, xpath):