D4292: pure: fix pure-Python revlog to support [0] lookups on empty log

[durin42 (Augie Fackler)]

durin42 created this revision.
Herald added a subscriber: mercurial-devel.
Herald added a reviewer: hg-reviewers.

REVISION SUMMARY
  This fixes many many test failures in pure mode, but it appears to be a material behavior difference from the cext version. I tried adding this test:
  
    def testindex0onemptyrevlog(self):
        want = (0, 0, 0, -1, -1, -1, -1, nullid)
        index, junk = parsers.parse_index2('', True)
        got = index[0]
        self.assertEqual(want, got)
  
  to test-parseindex2.py, and it fails on native (but passes --pure
  after this patch). I'm unclear what the correct behavior *should* be,
  but hopefully this guides someone to a fix...

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D4292

AFFECTED FILES
  mercurial/pure/parsers.py

CHANGE DETAILS

diff --git a/mercurial/pure/parsers.py b/mercurial/pure/parsers.py
--- a/mercurial/pure/parsers.py
+++ b/mercurial/pure/parsers.py
@@ -52,7 +52,7 @@
         return i
 
     def __getitem__(self, i):
-        if i == -1:
+        if i == -1 or i == len(self) == 0:
             return (0, 0, 0, -1, -1, -1, -1, nullid)
         i = self._fix_index(i)
         if i >= self._lgt:



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