# HG changeset patch
# User Martin von Zweigbergk <martinvonz@google.com>
# Date 2018-02-13 21:23:18
# Node ID b42c47b8c9d4c4f8c396915aa70d87a328a521b4
# Parent  8173eeb69fb3b3876c7baecf0a400fb97fabc759

treemanifest: add an optimized __nonzero__()

We use bool(manifest) in at least some places:

  localrepo.py:1730
  hgweb/webcommands.py:524

Since the treemanifest class doesn't define __nonzero__() (before this
patch), bool(manifest) will instead call __len__(), which can be slow
for treemanifests. This patch may make a noticeable difference in the
localrepo case above, but that only happens when committing a merge
and I haven't timed it.

Note that Durham already added a __nonzero__ implementation to
manifestdict in b19291e5d506 (manifest: add __nonzero__ method,
2016-11-03).

Differential Revision: https://phab.mercurial-scm.org/D2232

diff --git a/mercurial/manifest.py b/mercurial/manifest.py
--- a/mercurial/manifest.py
+++ b/mercurial/manifest.py
@@ -755,6 +755,12 @@ class treemanifest(object):
             size += m.__len__()
         return size
 
+    def __nonzero__(self):
+        # Faster than "__len() != 0" since it avoids loading sub-manifests
+        return not self._isempty()
+
+    __bool__ = __nonzero__
+
     def _isempty(self):
         self._load() # for consistency; already loaded by all callers
         return (not self._files and (not self._dirs or