D7271: linelog: be more careful about types before looking for _target attribute

[durin42 (Augie Fackler)]

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

REVISION SUMMARY
  Without this, pytype (correctly) complains that fakejge might not have
  a _cmprev attribute. We're operating on some constraints not
  expressible in the type system, so we detect the invalid case and
  raise a nicer exception now.
  
  Sadly, we also need an `assert` to give PyType a clue that we know
  what we're doing, but I can absolutely live with that.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D7271

AFFECTED FILES
  mercurial/linelog.py

CHANGE DETAILS

diff --git a/mercurial/linelog.py b/mercurial/linelog.py
--- a/mercurial/linelog.py
+++ b/mercurial/linelog.py
@@ -278,8 +278,14 @@
         fakejge = _decodeone(buf, 0)
         if isinstance(fakejge, _jump):
             maxrev = 0
+        elif isinstance(fakejge, (_jge, _jl)):
+            maxrev = fakejge._cmprev
         else:
-            maxrev = fakejge._cmprev
+            raise LineLogError(
+                'Expected one of _jump, _jge, or _jl. Got %s.'
+                % type(fakejge).__name__
+            )
+        assert isinstance(fakejge, (_jump, _jge, _jl))  # help pytype
         numentries = fakejge._target
         if expected != numentries:
             raise LineLogError(



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Cc: mercurial-devel