simplecache: fix for hggit

Summary:
When used with hggit, simplecache would treat all hggit overlayctxs as having the `nullid` node. This is used in the cache key for the result of `status()`; this caused the return value of all hggit's changectxs'  `status()` to be intermingled.

There are arguably two issues here:

- hggit's `overlaychangectx` simply implemented `node()` and didn't set a `_node` like changectx does. Changectx refers to this property internally (and other external callers might do so too) so we should probably set it.
- simplecache was reading the `changectx._node` property instead of the more public `changectx.node()`. This returned `nullid` because of the above.

Either change would fix it but I sent both to be safe. I look forward to tightening the context class interfaces in the future.

(Note: this ignores all push blocking failures!)

Reviewed By: quark-zju

Differential Revision: D6788335

fbshipit-source-id: eb4b3cebc1b6ee6011405cdb7d702cdf5cac0904

hgext/hggit/overlay.py

@@ -213,12 +213,13 @@ class overlaychangectx(context.changectx):
         self.commit = repo.handler.git.get_object(_maybehex(sha))
         self._overlay = getattr(repo, 'gitoverlay', repo)
         self._rev = self._overlay.rev(bin(self.commit.id))
+        self._node = bin(self.commit.id)
 
     def repo(self):
         return self._hgrepo
 
     def node(self):
-        return bin(self.commit.id)
+        return self._node
 
     def rev(self):
         return self._rev

hgext/simplecache.py

@@ -28,10 +28,21 @@ from mercurial import (
     extensions,
     node,
 )
+from mercurial.node import (
+    nullid,
+    wdirid
+)
 from mercurial.scmutil import status
 
 testedwith = 'ships-with-fb-hgext'
 
+# context nodes that are special and should not be cached.
+UNCACHEABLE_NODES = [
+    None, # repo[None].node() returns this
+    nullid,
+    wdirid
+]
+
 def extsetup(ui):
     extensions.wrapfunction(copies, 'pathcopies', pathcopiesui(ui))
     extensions.wrapfunction(context.basectx, '_buildstatus', buildstatusui(ui))
@@ -155,10 +166,11 @@ def buildstatusui(ui):
             return func()
         if ignored or clean or unknown:
             return func()
-        if self._node is None or other._node is None:
+        if (self.node() in UNCACHEABLE_NODES or
+            other.node() in UNCACHEABLE_NODES):
             return func()
         key = 'buildstatus:%s:%s' % (
-                node.hex(self._node), node.hex(other._node))
+                node.hex(self.node()), node.hex(other.node()))
         return memoize(func, key, buildstatusserializer, ui)
 
     return buildstatus