sidedata: check that the sidedata safely roundtrip

We actually use the data we stored during the test. It is a way to make sure
their content is not corrupted.

Differential Revision: https://phab.mercurial-scm.org/D6898

tests/testlib/ext-sidedata.py

@@ -1,36 +1,50 b''
 # ext-sidedata.py - small extension to test the sidedata logic
 #
 # Copyright 2019 Pierre-Yves David <[e-mail])
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import hashlib
 import struct
 
 from mercurial import (
     extensions,
+    node,
     revlog,
 )
 
 from mercurial.revlogutils import (
     sidedata,
 )
 
 def wrapaddrevision(orig, self, text, transaction, link, p1, p2, *args,
                     **kwargs):
     if kwargs.get('sidedata') is None:
         kwargs['sidedata'] = {}
     sd = kwargs['sidedata']
     ## let's store some arbitrary data just for testing
     # text length
     sd[sidedata.SD_TEST1] = struct.pack('>I', len(text))
     # and sha2 hashes
     sha256 = hashlib.sha256(text).digest()
     sd[sidedata.SD_TEST2] = struct.pack('>32s', sha256)
     return orig(self, text, transaction, link, p1, p2, *args, **kwargs)
 
+def wraprevision(orig, self, nodeorrev, *args, **kwargs):
+    text = orig(self, nodeorrev, *args, **kwargs)
+    if nodeorrev != node.nullrev and nodeorrev != node.nullid:
+        sd = self.sidedata(nodeorrev)
+        if len(text) != struct.unpack('>I', sd[sidedata.SD_TEST1])[0]:
+            raise RuntimeError('text size mismatch')
+        expected = sd[sidedata.SD_TEST2]
+        got = hashlib.sha256(text).digest()
+        if got != expected:
+            raise RuntimeError('sha256 mismatch')
+    return text
+
 def extsetup(ui):
     extensions.wrapfunction(revlog.revlog, 'addrevision', wrapaddrevision)
+    extensions.wrapfunction(revlog.revlog, 'revision', wraprevision)