[PATCH 07 of 14] cache: introduce a dualsourcebase class

[Boris Feld]

# HG changeset patch
# User Boris Feld <boris.feld at octobus.net>
# Date 1499458959 -7200
#      Fri Jul 07 22:22:39 2017 +0200
# Node ID 5d3e659c979aa428ba44b138cfac30b7cca28fb3
# Parent  5b49f653a4a50607127e37e7511c8a8e343cc8d9
# EXP-Topic obs-cache
cache: introduce a dualsourcebase class

This abstract class cover the case where cache are computed from data
contained in the changelog -and- the obsstore.

diff -r 5b49f653a4a5 -r 5d3e659c979a mercurial/cache.py
--- a/mercurial/cache.py	Fri Jul 07 22:22:04 2017 +0200
+++ b/mercurial/cache.py	Fri Jul 07 22:22:39 2017 +0200
@@ -181,3 +181,38 @@
 
     def _fetchupdatedata(self, repo):
         return repo.obsstore.getmarkerssince(self._cachekey)
+
+class dualsourcecache(obsstoresourcebase, changelogsourcebase):
+    """An abstract class for cache that needs both changelog and obsstore
+
+    The cache key used is a combinaison of the one used for the changelog and
+    the one used for the obsstore. See inherited class for details.
+    """
+
+    __metaclass__ = abc.ABCMeta
+
+    # default key used for an empty cache
+    emptykey = (changelogsourcebase.emptykey
+                + obsstoresourcebase.emptykey)
+    _cachekeyspec = (changelogsourcebase._cachekeyspec
+                     + obsstoresourcebase._cachekeyspec)
+    _cachename = None # used for debug message
+
+    def _fetchupdatedata(self, repo):
+        clkey = self._cachekey[0:2]
+        obskey = self._cachekey[2:4]
+
+        reset, revs, newclkey = self._fetchchangelogdata(clkey, repo.changelog)
+        if reset:
+            obskey = obsstoresourcebase.emptykey
+        obsreturn = repo.obsstore.getmarkerssince(obskey)
+        obsreset, obsmarkers, newobskey = obsreturn
+        if obsreset:
+            reset = True
+            clkey = changelogsourcebase.emptykey
+            clreturn = self._fetchchangelogdata(clkey, repo.changelog)
+            __, revs, newclkey = clreturn
+
+        newkey = newclkey + newobskey
+        data = (revs, obsmarkers)
+        return reset, data, newkey