[PATCH 1 of 4] basectx: cache filectx generation for all contexts

[Sean Farley]

# HG changeset patch
# User Sean Farley <sean.michael.farley at gmail.com>
# Date 1408408678 18000
#      Mon Aug 18 19:37:58 2014 -0500
# Node ID 594d00e49cea6cd2ebb92c0570e7502f8797e232
# Parent  8dda6f6ff564d8fe6ac7b8ce4c74eb9bfb5de14a
basectx: cache filectx generation for all contexts

Previously, filecontexts are generated on the fly but not cached. We need to
keep them around if we're going to allow the data inside to be changed. This
change is added to basectx so that other contexts that inherit can benefit as
well.

Currently, this is disabled for memctx objects that are passed a callable data
store function.

diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -31,10 +31,11 @@ class basectx(object):
         o = super(basectx, cls).__new__(cls)
 
         o._repo = repo
         o._rev = nullrev
         o._node = nullid
+        o._filectxs = {}
 
         return o
 
     def __str__(self):
         return short(self.node())
@@ -56,11 +57,20 @@ class basectx(object):
 
     def __contains__(self, key):
         return key in self._manifest
 
     def __getitem__(self, key):
-        return self.filectx(key)
+        try:
+            return self._filectxs[key]
+        except TypeError:
+            # filectx caching is not enabled
+            return self.filectx(key)
+        except KeyError:
+            v = self.filectx(key)
+            self._filectxs[key] = v
+            return v
+
 
     def __iter__(self):
         for f in sorted(self._manifest):
             yield f
 
@@ -1614,10 +1624,14 @@ class memctx(committablectx):
                     copied = copied[0]
                 return memfilectx(repo, path, fctx.data(),
                                   islink=fctx.islink(), isexec=fctx.isexec(),
                                   copied=copied, memctx=memctx)
             self._filectxfn = getfilectx
+        else:
+            # disable filectx caching for users that send in custom function,
+            # e.g. hg convert
+            self._filectxs = None
 
         self._extra = extra and extra.copy() or {}
         if self._extra.get('branch', '') == '':
             self._extra['branch'] = 'default'