[PATCH 4 of 4] manifest: change manifestctx to not inherit from manifestdict

[Durham Goode]

# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1472519937 25200
#      Mon Aug 29 18:18:57 2016 -0700
# Node ID 8076d529408e977951286dbd58e81066f97a9b8d
# Parent  4b26b5cd815a717ee0ee930f4deef0959ef7c492
manifest: change manifestctx to not inherit from manifestdict

If manifestctx inherits from manifestdict, it requires some weird logic to
lazily load the dict if a piece of information is asked for. This ended up being
complicated and unintuitive to use.

Let's move the dict creation to .read(). This will make even more sense once we
start adding readdelta() and other similar methods to manifestctx.

diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -528,7 +528,7 @@ class changectx(basectx):
 
     @propertycache
     def _manifest(self):
-        return self._repo.manifestlog[self._changeset.manifest]
+        return self._repo.manifestlog[self._changeset.manifest].read()
 
     @propertycache
     def _manifestdelta(self):
diff --git a/mercurial/manifest.py b/mercurial/manifest.py
--- a/mercurial/manifest.py
+++ b/mercurial/manifest.py
@@ -948,9 +948,9 @@ class manifestlog(object):
         """
         if node == revlog.nullid:
             if self._oldmanifest._treeinmem:
-                return treemanifest()
+                return treemanifestctx(self._revlog, node, dir='')
             else:
-                return manifestdict()
+                return manifestctx(self._revlog, node)
 
         if node in self._mancache:
             cachemf = self._mancache[node]
@@ -967,33 +967,38 @@ class manifestlog(object):
         self._mancache[node] = m
         return m
 
-class manifestctx(manifestdict):
+class manifestctx(object):
     """A class representing a single revision of a manifest, including its
     contents, its parent revs, and its linkrev.
     """
     def __init__(self, revlog, node):
         self._revlog = revlog
+        self._data = None
 
         self._node = node
         self.p1, self.p2 = revlog.parents(node)
         rev = revlog.rev(node)
         self.linkrev = revlog.linkrev(rev)
 
-        # This should eventually be made lazy loaded, so consumers can access
-        # the node/p1/linkrev data without having to parse the whole manifest.
-        data = revlog.revision(node)
-        arraytext = array.array('c', data)
-        revlog._fulltextcache[node] = arraytext
-        super(manifestctx, self).__init__(data)
-
     def node(self):
         return self._node
 
-class treemanifestctx(treemanifest):
+    def read(self):
+        if self._node == revlog.nullid:
+            return manifestdict()
+        if not self._data:
+            data = self._revlog.revision(self._node)
+            arraytext = array.array('c', data)
+            self._revlog._fulltextcache[self._node] = arraytext
+            self._data = manifestdict(data)
+        return self._data
+
+class treemanifestctx(object):
     def __init__(self, revlog, node, dir=''):
         revlog = revlog.dirlog(dir)
         self._revlog = revlog
         self._dir = dir
+        self._data = None
 
         self._node = node
 
@@ -1004,19 +1009,27 @@ class treemanifestctx(treemanifest):
         #rev = revlog.rev(node)
         #self.linkrev = revlog.linkrev(rev)
 
-        if revlog._treeondisk:
-            super(treemanifestctx, self).__init__(dir=dir)
-            def gettext():
-                return revlog.revision(node)
-            def readsubtree(dir, subm):
-                return revlog.dirlog(dir).read(subm)
-            self.read(gettext, readsubtree)
-            self.setnode(node)
-        else:
-            data = revlog.revision(node)
-            arraytext = array.array('c', data)
-            revlog.fulltextcache[node] = arraytext
-            super(treemanifestctx, self).__init__(dir=dir, text=data)
+    def read(self):
+        if self._node == revlog.nullid:
+            return treemanifest()
+
+        if not self._data:
+            if self._revlog._treeondisk:
+                treemf = treemanifest(dir=self._dir)
+                def gettext():
+                    return self._revlog.revision(self._node)
+                def readsubtree(dir, subm):
+                    return treemanifestctx(self._revlog, subm, dir).read()
+                treemf.read(gettext, readsubtree)
+                treemf.setnode(self._node)
+                self._data = treemf
+            else:
+                data = self._revlog.revision(self._node)
+                arraytext = array.array('c', data)
+                self._revlog.fulltextcache[self._node] = arraytext
+                self._data = treemanifest(dir=self._dir, text=data)
+
+        return self._data
 
 class manifest(manifestrevlog):
     def __init__(self, opener, dir='', dirlogcache=None):