# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 2014-10-15 11:26:23
# Node ID 2587631c5f8a15492fb6a41b232405e84496a2cc
# Parent  840be5ca03e1db16ba994e55597771c418166c97

revset: make __len__ part of the offical API

It is common for code to ask for the length of a revset. In fact, all but
generatorset already implement it.

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2255,6 +2255,12 @@ class abstractsmartset(object):
         Return None if the set is empty"""
         raise NotImplementedError()
 
+    def __len__(self):
+        """return the length of the smartsets
+
+        This can be expensive on smartset that could be lazy otherwise."""
+        raise NotImplementedError()
+
     def reverse(self):
         """reverse the expected iteration order"""
         raise NotImplementedError()